419
0 1992
The Japanese Society of Pathology
Histologic Changes in Graves’ Thyroid Gland after l3lI Therapy for Hyperthyroid ism
Yuji Mizukami’, Takatoshi Michigishi2, Akitaka Nonomural, Takuma Hashimoto3, Masakuni Noguchi4, Kenji Ohmura4 and Fujitsugu Matsubara’
The effect of l 3 l I therapy was examined in 13 thyroid glands affected by Graves’ disease 3 to 29 years after irradiation for hyperthyroidism. All of the patients had clinically palpable thyroid nodules. Two patients were in a latent hypothyroid, 6 in a euthyroid and 5 in a hyperthyroid state. The microscopic changes in the thyroids showed a pattern of multiple adenomatous nodules with cystic changes, marked oxyphilic cell changes with nuclear atypism and various degrees of chronic thyroiditis. lmmunohistochemical staining for TG and T, was negative t o mildly positive in these oxyphilic cells and entirely negative for EGF and CEA. The DNA ploidy pattern was diploid pattern in 6 cases. One papillary-type microcarcinoma occurred, but there was no evidence of a relationship between the tumor and the irradiation. The pathologic findings in therapy are not specific, but Graves’ thyroid gland after l3lI pathologists should differentiate this lesion f r o m adenomatous goiter, which occurs with no apparent cause, or from thyroid carcinoma because of the marked nuclear atypism of this lesion. Acta Pathol Jpn 42: 419-426, 1992.
Graves’ thyroid, I3’I therapy, Histology, Hypothyroidism
Key words:
Radioactive iodine (l3lI)has been used for treatment of hyperthyroidism associated with Graves’ disease. Many studies have documented thyroid dysfunction after this type of therapy, and in particular hypothyroidism has frequently been reported after l 3 l I therapy for hyperthy roidism(1-3). On the other hand, only a few reports Received November 18, 1991. Accepted for publication January 28, 1992. ‘Pathology Section, and Departments of 2Nuclear Medicine, 3Laboratory Medicine and ‘Surgery, Kanazawa University Hospital, Kanazawa. Mailing address : Yuji Mizukami, Pathology Section, Kanazawa University Hospital, 13-1, Takara-machi, Kanazawa 920, Japan.
have described morphologic changes in the Graves’ thyroid gland after lB1l therapy, and little information is available regarding the relationship between histologic changes in this condition and thyroid dysfunction (4-8). This report describes the clinical and pathologic findings in 13 patients with Graves’ disease who presented with palpable thyroid nodules between 3 and 29 years after therapy.
MATERIALS AND METHODS This study involved 13 patients seen at the Kanazawa University Hospital who presented with a history of radioactive iodine (l3ll)therapy for hyperthyroidism associated with Graves’ disease and who showed palpable thyroid nodules. The therapeutic dose of l 3 l I was known in 5 patients, and varied from 1.5 mCi to 48 mCi, but in the remaining 8 patients, the exact dose was unknown. Thyroid tissues were obtained 3 to 29 years after irradiation, by subtotal thyroidectomy in 5 cases, by open biopsy in 1 case and by large needle biopsy in the remainder. Subtotal thyroidectomy was carried out because of increasing goiter or because of the failure of l3lI therapy to control the thyrotoxic state. Thyroid tissues were fixed in 10% formalin, dehydrated, embedded in paraffin, sectioned at a thickness of 5 p m and stained with hematoxylin and eosin (HE). Histologic changes were identified and tabulated. In order to grade and compare the pathological changes from case to case, a scale of (+) to ( # ) was employed, with 1+ denoting only a small, single area of change, and 3+ indicating extensive changes in multiple areas of tissue. Immunohistochemical examination was performed in all cases using paraffin-embedded sections and the avidin-biotin-complex technique. The antibodies used were those against thyroglobulin (TG) (Ortho, Raritan, NJ, prediluted), thyroxine (T4) (Ortho, prediluted), car-
420
Graves' Thyroid after I3'I Therapy (Mizukami et a/.) Table 1. Clinical Data in 1 3 Patients with Radioiodine Therapy for Graves' Hyperthyroidism __ Patient Clinical Thyroid TRC MRC Age of Patient Age /Sex Diagnosis Function at Initial Radioiodine ~Treatment 33/F Adenomatous Latent 402 802 15 yr goiter hypothyroid Diffuse goiter Eut hyroid 0 80' 20 yr 461 F 39 IF Adenoma tous Euthyroid (-1 202 32 yr goiter 1602 2 4 yr 53/F Adenomatous Hyperthyroid 10' goiter 57 y r (48 mCi) 202 63/F Adenomatous Euthyroid (-1 goiter 38 /F Adenomatous Latent 102 a02 15yr goiter hypothyroid (-1 3202 2 0 yr 37 I F Adenomatous Euthyroid goiter 29/F Adenoma tous Hyperthyroid ne ne 18 y r goiter 72, F Multiple cysts Eut hyroid (-1 402 7 1 yr (6 mCi) 40/F Solitary nodule Hyperthyroid (-1 802 34 y r (3 mCi) 1602 3 2 yr 402 Adenomatous Euthyroid 5 4 IF goiter 102 1602 2 8 y r (1 5 mCi) 32 F Adenomatous Hyperthyroid goiter 802 Hyperthyroid 202 61/F Adenomatous 5 8 yr (6 mCi) goiter______. ~
Case
No 1
2 3 4 5 6 7 8 9 10 11 12 13 ~
~~
~~
~~
TRC, anti-thyroglobulin antibody ; MRC, anti-microsome antibody ; ne, not examined.
cinoembryonic antigen (CEA) (Ortho, prediluted), and epidermal growth factor (EGF) (Wakunaga Pharmaceuticals, Osaka, Japan, 1 : 100, monoclonal). Electron microscopic examination was available in one case (Case No. 8). DNA ploidy status was determined by flow cytometry using 50 p m thick paraffin-embedded sections by the method of Hedley et a/. (9).
RESULTS I. Clinical findings The clinical findings in each patient are shown in Table 1. The patients studied had received I3'l therapy for hyperthyroidism associated with Graves' disease. The age of the patients at the time of surgery or biopsy ranged from 2 9 to 7 2 years. All of the patients were female. The clinical diagnosis at the time of surgery or biopsy was adenomatous (multinodular) goiter in 10 patients, diffuse goiter in 1 patient, solitary nodule in 1 patient and multiple cysts in 1 patient. The thyroid function of all the patients was evaluated from the values of serum thyroxine (TJ, triiodothyronine (T3) and thyrotropin (TSH). Two patients had latent hypothyroidism with normal levels of T, and T, and elevated TSH levels. Six patients had euthyroidism and two of the 6 euthyroid patients had received ant ithyroid drug therapy following 13'1 therapy. Five patients still had hyperthyroidism.
Thyroid antibodies (thyroglobulin antibody, TRC, and microsome antibody, MRC) were examined in 1 2 patients. Six patients had both antibodies, and the remainder had only microsome antibody.
II. Pathologic findings The pathologic findings and pathologic diagnosis in each case are summarized in Table 2. The most striking and frequently seen abnormality was the presence of multiple adenomatous nodules (Fig. 1). They showed a variable colloid content and frequently were organized into macrofollicular patterns (Figs. 2, 3). The size of the nodules varied and the border of the nodules with the surrounding parenchyma was irregular. Some of the nodules were surrounded by a fibrous capsule. Others lacked such a capsule, but no invasive growth was associated. The surrounding parenchyma showed hyperplastic changes suggesting Graves' thyroid, including large follicular spaces with focal epithelial folding. The follicular cells in these nodules showed extensive oxyphilic changes, with an expanded granular cytoplasm, and often a larger, more pleomorphic nucleus (Figs. 4-6). In the center of the nodules, these oxyphilic cells had degenerated and disappeared, and subsequently cystic degeneration of the nodules was frequently observed (Fig. 7). Many nodular lesions were still evident, but nodules isolated and surrounded by a thick fibrous c a p sule, suggesting adenoma, were rarely observed. The
421
Acta Pathologica Japonica 42 (6) : 1992
Table 2. Histologic Evaluation of Thyroid Gland in 13 Patients Case No. -~
Ma teria I
1
NB
2
NB
3
NB
4
NB
5
NB
6
NB
7
NB
8
OB
9
STT
10
STT
11
STT
12
STT
13
STT
Lymphocytic Infiltration (9)
Fibrosis
Histologic Findings Epithelial Nuclear Ox y phiIia Atypism (it) (+I
-
Epithelial Hyperplasia
(-1
Pat hologica Diagnosis Chronic thyroiditis Chronic thyroiditis Hyperplastic thyroid Hyperplastic thyroid Adenomatous goiter Adenomatous goiter Adenomatous goiter Adenomatous goiter Adenoma tous goiter Graves' thyroid Adenoma tous goiter Graves' thyroid Adenomatous goiter Papillary carcinoma
NB, needle biopsy ; OB, open biopsy ; STT, subtotal thyroidectomy. (-), non; (+), mild; (it), moderate; (ik), marked.
Figure 1. Macroscopic appearance of thyroid gland (Case 8). Both thyroid lobes are enlarged and multiple nodules of various size are evident.
422
Graves’ Thyroid after
L3LI Therapy (Mizukami et
a/.)
Figure 2. Adenomatous nodule with cystic change. Early capsule formation is evident. Surrounding thyroid parenchyma reveals mild hyperplastic changes (Case 7) (HE). Figure 3. Adenomatous nodule with marked epithelial oxyphilia. Follicles are dilated and contain scant colloidal materials (Case 8) (HE). Figure 4. Oxyphilic cells with granular cytoplasm show a papillary arrangement. Nuclei are hyperchromatic, but nuclear atypia is not remarkable (Case 8) (HE). Figure 5. Tiny foci of epithelial oxyphilia are scattered within thyroid parenchyma showing hyperplastic changes (Case 11) (HE).
nuclear atypia of the follicular cells also appeared to be distributed in a random manner with follicles and nodules. Mitoses were rarely observed and the nuclear atypia appeared to be associated with cell degeneration, because it was predominant in the oxyphilic follicular cells. Diffuse hyperplasia composed of macrofollicles, resembling Graves’ thyroid, was seen in 2 cases. Compared with typical Graves’ thyroid, the follicular cells were cuboidal to flattened, and the papillary folding of the follicular cells into the lumen was not prominent (Fig. 8). Both of these patients were still in a hyperthyroid
state. Four of the 13cases (30%) showed mild to intense infiltration of lymphocytes, often with formation of germinal centers (Fig. 9). In these four cases, two were diagnosed histologically as chronic thyroiditis and one as latent hypothyroidism. Fibrosis, generally mild in degree, was present in 6cases, usually in the form of interlobular fibrosis. One patient was found to have a papillary carcinoma (Fig. 10). The size of the carcinoma was approximately 1.0 cm in diameter and was a microcarcinoma. The carcinoma cells showed somewhat degenerative
Acta Pathologica Japonica 42 (6): 1992
423
Figure 6. Oxyphilic cells with moderate nuclear atypia. Note variation in nuclear size, shape and chromatin distribution (Case 10) (HE).
Figure 7. In the center of adenomatous nodules, degenerative change and disruption of follicles is evident (Case 2) (HE).
Figure 8. Macrofollicles with mild hyperplastic changes, similar to those seen in Graves’ thyroid, are predominantly evident (Case 11) (HE).
Figure 9. Severe lymphocytic infiltration is a predominant histologic feature, indicating development of chronic thyroiditis (Case 1) (HE).
changes, probably due to the effect of the I8ll therapy. Therefore, this carcinoma was considered to have been present at the time of the therapy.
ing in their cytoplasm (Fig. 11). The immunostaining for EGF and CEA was negative in all cases.
IV.
111.
lmmunohistochemistry
lmmunostaining for TG and T, showed negative to mildly positive results in various areas of a single section in all cases. The oxyphilic cells showed negative stain-
Electron microscopy
Electron microscopic examination of the oxyphilic changed cells showed numerous, closely packed mitochondria in their cytoplasm. In the apical region of the cytoplasm, many dense bodies were also observed, but
424
Graves' Thyroid after I3lITherapy (Mizukami et a/.)
Figure 10. Association of papillary carcinoma. Carcinoma cells show somewhat degenerative changes, probably due t o l3II treatment (Case 13) (HE).
Figure 11. lmmunostaining for TG. Oxyphilic cells show positive staining only along the luminal surface. Cytoplasm shows negative staining (Case 10) (ABC method).
Figure 12. Electron micrograph of oxyphilic follicular cells. Cytoplasm is filled with numerous mitochondria. Many dense bodies are evident in the apical region (Case 8) ( ~ 5 , 2 0 0 ) .
development of the rough endoplasmic reticulum (rER) or Golgi apparatus was poor (Fig. 12). These ultrastructural findings suggested that these oxyphilic cells have no functional activity.
V.
DNA ploidy
All 6cases examined showed a diploid D N A pattern. Various degrees of nuclear atypism were associated in all 6 cases, but none showed D N A aneuploidy.
Acta Pathologica Japonica 42 (6): 1992
DISCUSSION It is known that the major complication of lS1ltherapy in hyperthyroidism associated with Graves' disease is a cumulative incidence of post-radiation hypothyroidism. The incidence of this complication varies in different series, ranging from as low as 15% to as high as 70% after 10 years (1-3). Our present study indicated two histological features therapy. One is to account for hypothyroidism after IS1l an association of chronic thyroiditis and the other is extensive oxyphilic changes in follicular cells. Lymphocytic infiltration was observed in 30% of the cases, and two cases were diagnosed as chronic thyroiditis because of extensive lymphocytic infiltration and lack of hyperplastic follicular changes. This might suggest the development of a cellular autoimmune reaction in the lS1l-treatedthyroid glands, possibly caused by physical damage to follicular cells with release of thyroglobulin and microsome antigens. This is supported by the higher incidence of thyroid autoantibody-positive cases in our series. Increase or development of thyroid autoantibodies after l3lI therapy for hyperthyroidism has also been reported (10, 11). Association of thyroiditis after low doses of radioiodine has also been described in rats (12). Extensive oxyphilic change in the follicular cells in l3lItreated thyroids are also an important histologic factor in accounting for hypothyroidism. Our ultrastructural observations showed that these oxyphilic cells were characterized by numerous mitochondria in their cytoplasm. In our previous study, cells showing oxyphilic change in chronic thyroiditis or in Graves' thyroids after long-term treatment with anti-thyroid drugs were found to lack peroxidase, an enzyme essential for thyroglobulin synthesis (13). The present immunohistochemical study also demonstrated that these oxyphilic cells synthesize no or only minimal amounts of thyroglobulin, and therefore this would have induced the hypothyroidism in these patients. The mechanism responsible for oxyphilic change in follicular cells after radiation has not been elucidated. Some studies have shown that such change is caused by a subsequent increase of TSH secretion (6, 14). However, we consider that irradiation changes primarily thyroid follicular cells into oxyphilic cells, and that thereafter, the serum TSH level increases due to a feedback mechanism. Of the present patients, two were latent hypothyroid, 6 euthyroid and 5 hyperthyroid. We consider that the above-mentioned two histologic features: association of chronic thyroiditis and extensive oxyphilic changes in follicular cells, are important causative factors of hypothyroidism after l9lltherapy. However, it might be
425
difficult to predict thyroid function after therapy only on the basis of the histologic appearance of the thyroid gland in each case. In two cases of latent hypothyroidism, chronic thyroiditis was found in only one, and epithelial oxyphilia was moderate in both. On the other hand, in five patients who remained hyperthyroid, various degrees of epithelia I hyperplasia remained, in associa tion with epithelial oxyphilia. Thus epithelial hyperplasia might also influence thyroid function. It has been shown that external irradiation of the thyroid in growing children can cause thyroid carcinoma (15-18). In 1950, Duffy and Fitzgerald (19) observed that 1 0 of 2 8 children with thyroid cancer had a history of previous neck irradiation. Fleming et a/. (20) reviewed 2 9 8 children who received low-dose neck irradiation and reported that thyroid cancer developed in two. Spitalnik and Straus (21) also reported that 59% of 68 patients who had received low-dose irradiation to the head and neck in childhood had papillary or follicular carcinoma in their thyroids. However, the number of adult patients developing thyroid carcinoma after therapeutic doses of IS1l is small (22,23). Kennedy and Thomson (4) reported one case of papillary carcinoma in 33 thyroid glands after I3lltherapy, and stated that there was no evidence of a causal relationship between carcinoma and I3lltherapy. In our present cases, only one had accompanying papillary microcarcinoma. However, this carcinoma was considered to have been present at the therapy. time of lB1I Marked nuclear atypia of follicular cells in the adenomatous nodules was a characteristic cytologic feature of lS1l-treatedthyroids, and this sometimes leads pathologists to a misdiagnosis of carcinoma. However, the absence of capsular invasion, the rarity of mitoses and the marked epithelial oxyphilia might support a benign diagnosis. Our immunohistochemical study showed that EGF was not expressed in oxyphilic cells with atypical nuclei. Our previous study indicated that most thyroid carcinoma cells expressed EGF to various degrees in their cytoplasm (24). DNA ploidy analysis also showed no aneuploid tumors in our series. This suggests that this nuclear atypism does not imply a precancerous condition, but a degenerative condition of follicular cells. Are the histologic findings observed in this study specific for Graves' thyroid glands after lS1I treatment ? Our previous study indicated that in the thyroid glands of patients with Graves' disease treated with anti-thyroid drugs for a long period, epithelial oxyphilia with nuclear a typism and lymphocytic infiltra tion developed focally, although these features were usually unaccompanied by diffuse adenomatous nodular changes or marked epithelial degeneration resulting in cyst formation (13, 25).
426
Graves' Thyroid after I3'lTherapy (Mizukami et a/.)
Adenomatous goiter which occurs with no apparent cause might also show a similar macroscopic appearance. However, it also does not show such extensive cystic changes, extensive epithelial oxyphilia or marked nuclear atypism, as observed in Graves' thyroids after 1 3 ' 1 therapy. In conclusion, thyroid tissues removed from patients after therapy for hyperthyroidism associated with Graves' disease revealed adenomatous nodular changes, cystic changes, oxyphilic cell changes with nuclear atypia and chronic thyroiditis t o various degrees. When encountering multiple adenomatous nodules with marked oxyphilic changes and nuclear atypia of the follicular cells, pathologists should ascertain whether the patient has a history of 1 3 ' 1 therapy.
11. 12. 13.
14.
15.
Acknowledgements : The authors thank Mrs. Sanae ltoh for preparation of the manuscript.
16.
REFERENCES
17.
1. Werner SC, Coelho B, and Quimby EH. Ten years results of 1 3 1 1 therapy of hyperthyroidism. Bull NY Acad Med 33 : 783-806, 1957. 2. Dunn JT and Chapman EM. Rising incidence of hypothyroidism after radioactive-iodine therapy in thyrotoxicosis. N Engl J Med 271: 1037-1042, 1964. 3. Nofal MM, Beierwaltes WH, and Pantno ME. Treatment of hyperthyroidism with sodium iodine 1-131. JAMA 197 : 605-610, 1966. 4. Kennedy JS and Thomson JA. The changes in the thyroid gland after irradiation with I3ll or partial thyroidectomy for thyrotoxicosis. J Pathol 112: 6581, 1974. 5. Dobyns BM, Vickery AL, Maloof F, and Chapman EM. Functional and histologic effects of therapeutic doses of radioactive iodine on the thyroid of man. J Clin Endocrinol Metab 1 3 : 548-567, 1953. 6. Sheline GE, Lindsay S,McCormack KR, and Galante M. Thyroid nodules occurring late after treatment of thyrotoxicosis with radioiodine. J Clin Endocrinol Metab 2 2 : 8-18, 1962. 7. Curran RC, Eckert H, and Wilson GM. The thyroid gland after treatment of hyperthyroidism by partial thyroidectomy or iodine 1-131. J Pathol Bacteriol 76: 541 -560, 1958. 8. Vickery AL Jr. Thyroid alterations due to irradiation. In International Academy of Pathology, ed. The T h y roid. Williams & Wilkins, 1964: 184-206. 9. Hedley DW, Fiedlander ML, Taylor IW, et a/, Method for analysis of cellular DNA content of paraffin-embedded pathological material using flow cytometry. J Histochem Cytochem 3 1 : 1333-1335, 1983. 10. Einhorn J, Fagraeus A, and Jonsson J. Thyroid anti-
18.
19. 20.
21. 22. 2 3.
24.
25.
bodies after l 3 l I treatment for hyperthyroidism. J Clin Endocrinol Metab 2 5 : 1218-1224, 1965. Eihorn J, Fagraeus A, and Jonsson J. Thyroid antibodies in euthyroid subjects after iodine-1 31 therapy. Radiat Res 28: 296-301, 1966. Potter GD, Lindsay S, and Chaikoff IL. Induction of neoplasms in rat thyroid glands by low doses of radioiodine. Arch Pathol 69 : 257-269, 1960. Mizukami Y and Matsubara F. An enzyme histochemistry and electron microscopic study of chronic thyroiditis and Graves' disease. Nippon Naibunpi Gakkai Zasshi 5 6 : 241-250, 1980 (in Japanese). Lindsay S and Jenks PR. Enzyme histochemistry of the thyroid gland. Fourth Int. Goitre Conf., London, July 1960 (Abstract) (Excerpta Medica Int. Congress Series, No. 26). New York, 1960: 29-30. Becker FO, Economou SG, Southwick HW, and Eisenstein R. Adult thyroid cancer after head and neck irradiation in infancy and childhood. Ann Intern Med 8 3 : 347-351, 1975. Favus MJ, Schneider AB, Stachura ME, et a/. Thyroid cancer occurring as a late consequence of head and neck irradiation. N Engl J Med 294: 1019-1025, 1976. Hempelmann LH, Hall WJ, Phillips M, et a/. Neoplasms in persons treated with x-rays in infancy: Fourth survey in 20 years. J Natl Cancer lnst 5 5 : 5 19-530, 1975. Refetoff S, Harrison J, Karanfilski BT, et a/. Continuing occurrence of thyroid carcinoma after irradiation to the neck in infancy and childhood. N Engl J Med 292 : 171-175, 1975. Duffy BJ and Fitzgerald PJ. Cancer of the thyroid in children: A report of 28cases. J Clin Endocrinol Metab 1 0 : 1296-1308, 1950. Fleming ID, Black TL, Thompson El, et a/. Thyroid dysfunction and neoplasia in children receiving neck irradiation for cancer. Cancer 5 5 : 1190-1194, 1985. Spitalnik PF and Straus FH. Patterns of human thyroid parenchymal reaction following low-dose childhood irradiation. Cancer 41 : 1098-1105, 1978. Burke G, Levinson MJ, and Zitman IH. Thyroid carcinoma ten years after sodium iodine l 3 l I treatment. JAMA 199: 247-251, 1967. McDougall IR, Kennedy JS, and Thomson JA. Thyroid carcinoma following iodine-131 therapy. Report of a case and review of the literature. J Clin Endocrinol Metab 3 3 : 287-292, 1971. Mizukami Y, Nonomura A, Hashimoto T, et a/. Immunohistochemical demonstration of epidermal growth factor and c-myc oncogene product in normal, benign and malignant thyroid tissues. Histopathology 18: 11-18, 1991. Mizukami Y, Michigishi T, Kawato M, et a/. Chronic thyroiditis. Thyroid function and histologic correlations in 601 cases. Hum Pathol (in press).
0 1992
The Japanese Society of Pathology
Histologic Changes in Graves’ Thyroid Gland after l3lI Therapy for Hyperthyroid ism
Yuji Mizukami’, Takatoshi Michigishi2, Akitaka Nonomural, Takuma Hashimoto3, Masakuni Noguchi4, Kenji Ohmura4 and Fujitsugu Matsubara’
The effect of l 3 l I therapy was examined in 13 thyroid glands affected by Graves’ disease 3 to 29 years after irradiation for hyperthyroidism. All of the patients had clinically palpable thyroid nodules. Two patients were in a latent hypothyroid, 6 in a euthyroid and 5 in a hyperthyroid state. The microscopic changes in the thyroids showed a pattern of multiple adenomatous nodules with cystic changes, marked oxyphilic cell changes with nuclear atypism and various degrees of chronic thyroiditis. lmmunohistochemical staining for TG and T, was negative t o mildly positive in these oxyphilic cells and entirely negative for EGF and CEA. The DNA ploidy pattern was diploid pattern in 6 cases. One papillary-type microcarcinoma occurred, but there was no evidence of a relationship between the tumor and the irradiation. The pathologic findings in therapy are not specific, but Graves’ thyroid gland after l3lI pathologists should differentiate this lesion f r o m adenomatous goiter, which occurs with no apparent cause, or from thyroid carcinoma because of the marked nuclear atypism of this lesion. Acta Pathol Jpn 42: 419-426, 1992.
Graves’ thyroid, I3’I therapy, Histology, Hypothyroidism
Key words:
Radioactive iodine (l3lI)has been used for treatment of hyperthyroidism associated with Graves’ disease. Many studies have documented thyroid dysfunction after this type of therapy, and in particular hypothyroidism has frequently been reported after l 3 l I therapy for hyperthy roidism(1-3). On the other hand, only a few reports Received November 18, 1991. Accepted for publication January 28, 1992. ‘Pathology Section, and Departments of 2Nuclear Medicine, 3Laboratory Medicine and ‘Surgery, Kanazawa University Hospital, Kanazawa. Mailing address : Yuji Mizukami, Pathology Section, Kanazawa University Hospital, 13-1, Takara-machi, Kanazawa 920, Japan.
have described morphologic changes in the Graves’ thyroid gland after lB1l therapy, and little information is available regarding the relationship between histologic changes in this condition and thyroid dysfunction (4-8). This report describes the clinical and pathologic findings in 13 patients with Graves’ disease who presented with palpable thyroid nodules between 3 and 29 years after therapy.
MATERIALS AND METHODS This study involved 13 patients seen at the Kanazawa University Hospital who presented with a history of radioactive iodine (l3ll)therapy for hyperthyroidism associated with Graves’ disease and who showed palpable thyroid nodules. The therapeutic dose of l 3 l I was known in 5 patients, and varied from 1.5 mCi to 48 mCi, but in the remaining 8 patients, the exact dose was unknown. Thyroid tissues were obtained 3 to 29 years after irradiation, by subtotal thyroidectomy in 5 cases, by open biopsy in 1 case and by large needle biopsy in the remainder. Subtotal thyroidectomy was carried out because of increasing goiter or because of the failure of l3lI therapy to control the thyrotoxic state. Thyroid tissues were fixed in 10% formalin, dehydrated, embedded in paraffin, sectioned at a thickness of 5 p m and stained with hematoxylin and eosin (HE). Histologic changes were identified and tabulated. In order to grade and compare the pathological changes from case to case, a scale of (+) to ( # ) was employed, with 1+ denoting only a small, single area of change, and 3+ indicating extensive changes in multiple areas of tissue. Immunohistochemical examination was performed in all cases using paraffin-embedded sections and the avidin-biotin-complex technique. The antibodies used were those against thyroglobulin (TG) (Ortho, Raritan, NJ, prediluted), thyroxine (T4) (Ortho, prediluted), car-
420
Graves' Thyroid after I3'I Therapy (Mizukami et a/.) Table 1. Clinical Data in 1 3 Patients with Radioiodine Therapy for Graves' Hyperthyroidism __ Patient Clinical Thyroid TRC MRC Age of Patient Age /Sex Diagnosis Function at Initial Radioiodine ~Treatment 33/F Adenomatous Latent 402 802 15 yr goiter hypothyroid Diffuse goiter Eut hyroid 0 80' 20 yr 461 F 39 IF Adenoma tous Euthyroid (-1 202 32 yr goiter 1602 2 4 yr 53/F Adenomatous Hyperthyroid 10' goiter 57 y r (48 mCi) 202 63/F Adenomatous Euthyroid (-1 goiter 38 /F Adenomatous Latent 102 a02 15yr goiter hypothyroid (-1 3202 2 0 yr 37 I F Adenomatous Euthyroid goiter 29/F Adenoma tous Hyperthyroid ne ne 18 y r goiter 72, F Multiple cysts Eut hyroid (-1 402 7 1 yr (6 mCi) 40/F Solitary nodule Hyperthyroid (-1 802 34 y r (3 mCi) 1602 3 2 yr 402 Adenomatous Euthyroid 5 4 IF goiter 102 1602 2 8 y r (1 5 mCi) 32 F Adenomatous Hyperthyroid goiter 802 Hyperthyroid 202 61/F Adenomatous 5 8 yr (6 mCi) goiter______. ~
Case
No 1
2 3 4 5 6 7 8 9 10 11 12 13 ~
~~
~~
~~
TRC, anti-thyroglobulin antibody ; MRC, anti-microsome antibody ; ne, not examined.
cinoembryonic antigen (CEA) (Ortho, prediluted), and epidermal growth factor (EGF) (Wakunaga Pharmaceuticals, Osaka, Japan, 1 : 100, monoclonal). Electron microscopic examination was available in one case (Case No. 8). DNA ploidy status was determined by flow cytometry using 50 p m thick paraffin-embedded sections by the method of Hedley et a/. (9).
RESULTS I. Clinical findings The clinical findings in each patient are shown in Table 1. The patients studied had received I3'l therapy for hyperthyroidism associated with Graves' disease. The age of the patients at the time of surgery or biopsy ranged from 2 9 to 7 2 years. All of the patients were female. The clinical diagnosis at the time of surgery or biopsy was adenomatous (multinodular) goiter in 10 patients, diffuse goiter in 1 patient, solitary nodule in 1 patient and multiple cysts in 1 patient. The thyroid function of all the patients was evaluated from the values of serum thyroxine (TJ, triiodothyronine (T3) and thyrotropin (TSH). Two patients had latent hypothyroidism with normal levels of T, and T, and elevated TSH levels. Six patients had euthyroidism and two of the 6 euthyroid patients had received ant ithyroid drug therapy following 13'1 therapy. Five patients still had hyperthyroidism.
Thyroid antibodies (thyroglobulin antibody, TRC, and microsome antibody, MRC) were examined in 1 2 patients. Six patients had both antibodies, and the remainder had only microsome antibody.
II. Pathologic findings The pathologic findings and pathologic diagnosis in each case are summarized in Table 2. The most striking and frequently seen abnormality was the presence of multiple adenomatous nodules (Fig. 1). They showed a variable colloid content and frequently were organized into macrofollicular patterns (Figs. 2, 3). The size of the nodules varied and the border of the nodules with the surrounding parenchyma was irregular. Some of the nodules were surrounded by a fibrous capsule. Others lacked such a capsule, but no invasive growth was associated. The surrounding parenchyma showed hyperplastic changes suggesting Graves' thyroid, including large follicular spaces with focal epithelial folding. The follicular cells in these nodules showed extensive oxyphilic changes, with an expanded granular cytoplasm, and often a larger, more pleomorphic nucleus (Figs. 4-6). In the center of the nodules, these oxyphilic cells had degenerated and disappeared, and subsequently cystic degeneration of the nodules was frequently observed (Fig. 7). Many nodular lesions were still evident, but nodules isolated and surrounded by a thick fibrous c a p sule, suggesting adenoma, were rarely observed. The
421
Acta Pathologica Japonica 42 (6) : 1992
Table 2. Histologic Evaluation of Thyroid Gland in 13 Patients Case No. -~
Ma teria I
1
NB
2
NB
3
NB
4
NB
5
NB
6
NB
7
NB
8
OB
9
STT
10
STT
11
STT
12
STT
13
STT
Lymphocytic Infiltration (9)
Fibrosis
Histologic Findings Epithelial Nuclear Ox y phiIia Atypism (it) (+I
-
Epithelial Hyperplasia
(-1
Pat hologica Diagnosis Chronic thyroiditis Chronic thyroiditis Hyperplastic thyroid Hyperplastic thyroid Adenomatous goiter Adenomatous goiter Adenomatous goiter Adenomatous goiter Adenoma tous goiter Graves' thyroid Adenoma tous goiter Graves' thyroid Adenomatous goiter Papillary carcinoma
NB, needle biopsy ; OB, open biopsy ; STT, subtotal thyroidectomy. (-), non; (+), mild; (it), moderate; (ik), marked.
Figure 1. Macroscopic appearance of thyroid gland (Case 8). Both thyroid lobes are enlarged and multiple nodules of various size are evident.
422
Graves’ Thyroid after
L3LI Therapy (Mizukami et
a/.)
Figure 2. Adenomatous nodule with cystic change. Early capsule formation is evident. Surrounding thyroid parenchyma reveals mild hyperplastic changes (Case 7) (HE). Figure 3. Adenomatous nodule with marked epithelial oxyphilia. Follicles are dilated and contain scant colloidal materials (Case 8) (HE). Figure 4. Oxyphilic cells with granular cytoplasm show a papillary arrangement. Nuclei are hyperchromatic, but nuclear atypia is not remarkable (Case 8) (HE). Figure 5. Tiny foci of epithelial oxyphilia are scattered within thyroid parenchyma showing hyperplastic changes (Case 11) (HE).
nuclear atypia of the follicular cells also appeared to be distributed in a random manner with follicles and nodules. Mitoses were rarely observed and the nuclear atypia appeared to be associated with cell degeneration, because it was predominant in the oxyphilic follicular cells. Diffuse hyperplasia composed of macrofollicles, resembling Graves’ thyroid, was seen in 2 cases. Compared with typical Graves’ thyroid, the follicular cells were cuboidal to flattened, and the papillary folding of the follicular cells into the lumen was not prominent (Fig. 8). Both of these patients were still in a hyperthyroid
state. Four of the 13cases (30%) showed mild to intense infiltration of lymphocytes, often with formation of germinal centers (Fig. 9). In these four cases, two were diagnosed histologically as chronic thyroiditis and one as latent hypothyroidism. Fibrosis, generally mild in degree, was present in 6cases, usually in the form of interlobular fibrosis. One patient was found to have a papillary carcinoma (Fig. 10). The size of the carcinoma was approximately 1.0 cm in diameter and was a microcarcinoma. The carcinoma cells showed somewhat degenerative
Acta Pathologica Japonica 42 (6): 1992
423
Figure 6. Oxyphilic cells with moderate nuclear atypia. Note variation in nuclear size, shape and chromatin distribution (Case 10) (HE).
Figure 7. In the center of adenomatous nodules, degenerative change and disruption of follicles is evident (Case 2) (HE).
Figure 8. Macrofollicles with mild hyperplastic changes, similar to those seen in Graves’ thyroid, are predominantly evident (Case 11) (HE).
Figure 9. Severe lymphocytic infiltration is a predominant histologic feature, indicating development of chronic thyroiditis (Case 1) (HE).
changes, probably due to the effect of the I8ll therapy. Therefore, this carcinoma was considered to have been present at the time of the therapy.
ing in their cytoplasm (Fig. 11). The immunostaining for EGF and CEA was negative in all cases.
IV.
111.
lmmunohistochemistry
lmmunostaining for TG and T, showed negative to mildly positive results in various areas of a single section in all cases. The oxyphilic cells showed negative stain-
Electron microscopy
Electron microscopic examination of the oxyphilic changed cells showed numerous, closely packed mitochondria in their cytoplasm. In the apical region of the cytoplasm, many dense bodies were also observed, but
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Graves' Thyroid after I3lITherapy (Mizukami et a/.)
Figure 10. Association of papillary carcinoma. Carcinoma cells show somewhat degenerative changes, probably due t o l3II treatment (Case 13) (HE).
Figure 11. lmmunostaining for TG. Oxyphilic cells show positive staining only along the luminal surface. Cytoplasm shows negative staining (Case 10) (ABC method).
Figure 12. Electron micrograph of oxyphilic follicular cells. Cytoplasm is filled with numerous mitochondria. Many dense bodies are evident in the apical region (Case 8) ( ~ 5 , 2 0 0 ) .
development of the rough endoplasmic reticulum (rER) or Golgi apparatus was poor (Fig. 12). These ultrastructural findings suggested that these oxyphilic cells have no functional activity.
V.
DNA ploidy
All 6cases examined showed a diploid D N A pattern. Various degrees of nuclear atypism were associated in all 6 cases, but none showed D N A aneuploidy.
Acta Pathologica Japonica 42 (6): 1992
DISCUSSION It is known that the major complication of lS1ltherapy in hyperthyroidism associated with Graves' disease is a cumulative incidence of post-radiation hypothyroidism. The incidence of this complication varies in different series, ranging from as low as 15% to as high as 70% after 10 years (1-3). Our present study indicated two histological features therapy. One is to account for hypothyroidism after IS1l an association of chronic thyroiditis and the other is extensive oxyphilic changes in follicular cells. Lymphocytic infiltration was observed in 30% of the cases, and two cases were diagnosed as chronic thyroiditis because of extensive lymphocytic infiltration and lack of hyperplastic follicular changes. This might suggest the development of a cellular autoimmune reaction in the lS1l-treatedthyroid glands, possibly caused by physical damage to follicular cells with release of thyroglobulin and microsome antigens. This is supported by the higher incidence of thyroid autoantibody-positive cases in our series. Increase or development of thyroid autoantibodies after l3lI therapy for hyperthyroidism has also been reported (10, 11). Association of thyroiditis after low doses of radioiodine has also been described in rats (12). Extensive oxyphilic change in the follicular cells in l3lItreated thyroids are also an important histologic factor in accounting for hypothyroidism. Our ultrastructural observations showed that these oxyphilic cells were characterized by numerous mitochondria in their cytoplasm. In our previous study, cells showing oxyphilic change in chronic thyroiditis or in Graves' thyroids after long-term treatment with anti-thyroid drugs were found to lack peroxidase, an enzyme essential for thyroglobulin synthesis (13). The present immunohistochemical study also demonstrated that these oxyphilic cells synthesize no or only minimal amounts of thyroglobulin, and therefore this would have induced the hypothyroidism in these patients. The mechanism responsible for oxyphilic change in follicular cells after radiation has not been elucidated. Some studies have shown that such change is caused by a subsequent increase of TSH secretion (6, 14). However, we consider that irradiation changes primarily thyroid follicular cells into oxyphilic cells, and that thereafter, the serum TSH level increases due to a feedback mechanism. Of the present patients, two were latent hypothyroid, 6 euthyroid and 5 hyperthyroid. We consider that the above-mentioned two histologic features: association of chronic thyroiditis and extensive oxyphilic changes in follicular cells, are important causative factors of hypothyroidism after l9lltherapy. However, it might be
425
difficult to predict thyroid function after therapy only on the basis of the histologic appearance of the thyroid gland in each case. In two cases of latent hypothyroidism, chronic thyroiditis was found in only one, and epithelial oxyphilia was moderate in both. On the other hand, in five patients who remained hyperthyroid, various degrees of epithelia I hyperplasia remained, in associa tion with epithelial oxyphilia. Thus epithelial hyperplasia might also influence thyroid function. It has been shown that external irradiation of the thyroid in growing children can cause thyroid carcinoma (15-18). In 1950, Duffy and Fitzgerald (19) observed that 1 0 of 2 8 children with thyroid cancer had a history of previous neck irradiation. Fleming et a/. (20) reviewed 2 9 8 children who received low-dose neck irradiation and reported that thyroid cancer developed in two. Spitalnik and Straus (21) also reported that 59% of 68 patients who had received low-dose irradiation to the head and neck in childhood had papillary or follicular carcinoma in their thyroids. However, the number of adult patients developing thyroid carcinoma after therapeutic doses of IS1l is small (22,23). Kennedy and Thomson (4) reported one case of papillary carcinoma in 33 thyroid glands after I3lltherapy, and stated that there was no evidence of a causal relationship between carcinoma and I3lltherapy. In our present cases, only one had accompanying papillary microcarcinoma. However, this carcinoma was considered to have been present at the therapy. time of lB1I Marked nuclear atypia of follicular cells in the adenomatous nodules was a characteristic cytologic feature of lS1l-treatedthyroids, and this sometimes leads pathologists to a misdiagnosis of carcinoma. However, the absence of capsular invasion, the rarity of mitoses and the marked epithelial oxyphilia might support a benign diagnosis. Our immunohistochemical study showed that EGF was not expressed in oxyphilic cells with atypical nuclei. Our previous study indicated that most thyroid carcinoma cells expressed EGF to various degrees in their cytoplasm (24). DNA ploidy analysis also showed no aneuploid tumors in our series. This suggests that this nuclear atypism does not imply a precancerous condition, but a degenerative condition of follicular cells. Are the histologic findings observed in this study specific for Graves' thyroid glands after lS1I treatment ? Our previous study indicated that in the thyroid glands of patients with Graves' disease treated with anti-thyroid drugs for a long period, epithelial oxyphilia with nuclear a typism and lymphocytic infiltra tion developed focally, although these features were usually unaccompanied by diffuse adenomatous nodular changes or marked epithelial degeneration resulting in cyst formation (13, 25).
426
Graves' Thyroid after I3'lTherapy (Mizukami et a/.)
Adenomatous goiter which occurs with no apparent cause might also show a similar macroscopic appearance. However, it also does not show such extensive cystic changes, extensive epithelial oxyphilia or marked nuclear atypism, as observed in Graves' thyroids after 1 3 ' 1 therapy. In conclusion, thyroid tissues removed from patients after therapy for hyperthyroidism associated with Graves' disease revealed adenomatous nodular changes, cystic changes, oxyphilic cell changes with nuclear atypia and chronic thyroiditis t o various degrees. When encountering multiple adenomatous nodules with marked oxyphilic changes and nuclear atypia of the follicular cells, pathologists should ascertain whether the patient has a history of 1 3 ' 1 therapy.
11. 12. 13.
14.
15.
Acknowledgements : The authors thank Mrs. Sanae ltoh for preparation of the manuscript.
16.
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