Choristomas of the oral cavity: A review Laisheng Chou, DA4D,a Louis S. Hansen, DDS, MS, MBA,b and Troy E. Daniels, DDS, MS,c San Francisco, Calif. DIVISION

OF ORAL

PATHOLOGY,

SCHOOL

OF DENTISTRY,

UNIVERSITY

OF CALIFORNIA,

SAN

FRANCISCO The choristoma is a tumorlike mass of normal cells in an abnormal location. Intraoral choristomas been reported under a wide variety of names. This comprehensive review of the English-language on oral choristomas offers a classification of these lesions, analyzes their clinical and histologic and discusses possible pathogeneses and treatment. (ORAL SURC ORAL MED ORAL PATHOL 1991;72:584-93)

T he term

“choristoma” applies to a cohesive tumorlike mass consisting of normal cells in an abnormal location. It is thus distinguished from the hamartoma, a tumorlike malformation composed of a focal overgrowth of mature normal cells located where they are normally found. Both are distinguished from benign neoplasms. Intraoral tumorlike masses of normal but heterotopic cells that fit the definition of choristoma have been reported under a variety of other terms according to the type of dislocated cells. Many of the terms commonly applied are inappropriate; for example, “tumor” does not reflect the nonneoplastic clinical behavior and microscopic pattern, and “heterotopia” does not convey the appearance of a tumorlike mass. Only a few studies have been reported on choristomas in oral regions, and a classification of these lesions is not available. We attempted to trace all available cases in the English-language literature and include them in this comprehensive review article. Our purpose was to formulate a primary classification of choristomas of the oral cavity, to analyze the clinical and histomorphologic features, and to discuss the terminology and pathogenesis of each distinct entity in the classification.

“Postdoctoral Fellow; now at Faculty of British Columbia, Vancouver. bProfessor. cProfessor and Chairman. 7114128233

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The University

MATERIAL

have literature features,

AND METHODS

For the study a MEDLINE search of the Englishlanguage literature from 1966 through 1987 was performed with the use of the following Medical Subject Headings: “choristoma”; “hamartoma”; “osteoma”; “chondroma”; and “glioma”; together with “jaw,” “mandibular,” “maxillary,” “head and neck,” “mouth,” and “oropharyngeal neoplasma”; and “thyroid gland” together with “tongue” and with “tongue neoplasms.” A supplemental manual search was performed to trace appropriate cases reported before 1966. The criteria for including previously reported cases were as follows: l Clinically, the lesion presented as a tumorlike growth in soft tissue or as a radiolucency in the jaws. l Histologically, the dislocated tissues exhibited a normal pattern, with no neoplastic features. l The tissues were of a type not normally found in the region. On the basis of the various types of tissues recognized, the lesions were assigned to one of the following categories: 1. Salivary gland choristoma a. Central b. Gingival 2. Cartilaginous choristoma 3. Osseous choristoma 4. Lingua1 thyroid choristoma 5. Lingual sebaceous choristoma 6. Glial choristoma 7. Gastric mucosal choristoma

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a. Cystic b. Solid Ectopic lymphoid tissuelm4 in the oral cavity usually presents as a component of the lymphoepithelial cyst, and oral lesions containing respiratory epithelium5 are considered to be a form of metaplasia. Therefore they were excluded. Examples of a tumorlike mass with hair follicles on gingiva6 and skeletal muscle in the area of the maxillary lateral incisor and its attachment to the overlying mucosa’ have been reported. Although these single cases fulfill the criteria for choristoma, establishing new entities of intraoral hair follicle choristoma and intraoral skeletal muscle choristoma requires the accumulation of additional qualified cases for analysis. RESULTS AND DISCUSSION Salivary gland choristoma

Tumorlike masses of aberrant salivary gland tissue in the oral cavity have been reported with some regularity under various names. However, our search revealed only 23 cases that had been examined histologically or by sialographys2* and many were not choristomas. In 14 of these cases the salivary gland tissue was present in an indentation on the mandibular lingual surface or as a pedunculated mass extending into the mandible through a perforation of the inner plate with a connection to the submandibular or sublingual glands. *-19 Because of the salivary gland connection, these cases were not considered to fulfill the criteria of choristoma. In five cases, however, the salivary gland tissue was completely enclaved in the mandible. These lesions were variously termed “latent” or “static bone cyst,” “salivary gland inclusion in the mandible,” and “aberrant salivary gland defect.“20-24 In the remaining four cases the aberrant salivary gland tissue was situated in the attached gingiva and called “gingival salivary gland choristoma 9925-28 The term “latent” or “static bone cyst,” established by Stafne,29 implies only a cavity located between the mandibular canal and the angle and does not specify the nature and content of the cavity. Nonneoplastic aberrant or ectopic salivary gland tissue appearing either as a raised tumorlike mass or as a tumorlike radiolucency probably represents a single clinical entity, and the term “salivary gland choristoma” would be a more accurate description for these lesions. The lesions may be subclassified as central and gingival salivary gland choristoma, according to their specific location. Central salivary gland choristoma. Central sali-

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vary gland choristoma is a rare lesion, defined as an encapsulated solid mass of salivary gland tissue entirely enclaved in the mandible by intact cortical plates, with no evidence of connection to the submandibular or sublingual glands. Five reported cases could be placed in this subclassification. Four occurred in the anterior aspect of the mandible,20> 22-24 and one in the angle of the mandible around the cana1.21Three cases were in men, and two in women; age at diagnosis ranged from 26 to 53 years. This lesion has not been reported in a child. Clinically, the lesions appeared as round or oval, well-circumscribed radiolucencies, with fairly well-defined sclerotic borders, measuring 0.5 to 2.5 cm in diameter. Tenderness at the site of the lesion, an occasional complaint,23 was possibly due to compression by limited mucous excretion from the enclaved salivary gland nodule. Two possible origins for these central lesions were given: (1) mucous metaplasia of the lining epithelium of an odontogenic cyst*i$ 3o and (2) embryologically entrapped retromolar mucous salivary gland tissue. 1o131,32Although it is conceivable that the epithelial lining of odontogenic cysts may exhibit isolated areas of mucous metaplasia, it is unlikely that this epithelium can differentiate into normal salivary gland tissue. 21 The second theory also fails to explain the origin of a lesion occurring in the anterior mandible. With regard to the innocent nature and relatively small size of the intraosseous gland, we presume that the lesion may differentiate and develop from multipotential ectodermal cells within the mandible. The intraosseous salivary gland tissue is presumed to be nonfunctional and somewhat quiescent, like remnants of dental lamina. Gingivai salivary gland choristoma. The gingival salivary gland choristoma was first reported by Moskow and Baden in 1964, who described it as a tumorlike mass of the gingiva consisting of normal salivary tissue. We found a total of four reported cases.25-28 Of these four cases, two were in male patients25, 26 and one in a female, 28whereas in another case sex was not specified. 27 The age at diagnosis ranged from 9 to 44 years. Recorded locations were gingiva of the anterior maxilla (two cases), gingiva of third mandibular molar (one case), and gingiva of the anterior mandible (one case). All the lesions appeared clinically as asymptomatic, solitary, tumorlike masses of soft tissue in buccal or lingual gingiva, measuring 0.5 to 1.5 cm in diameter. No bony involvement was observed. TWO possibilities regarding the origin of gingival salivary gland choristoma have been proposed*s* 33,34:

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( 1) developmental displacement of minor salivary gland tissue and (2) metaplasia from multipotential gingival epithelium. With regard to the former, it is conceivable that during growth and development some of the salivary gland tissue normally located in oral mucosa becomes entrapped and remains in the gingiva, where it produces a clinical mass. However, the precise pathogenesis is still debatable. General comments. Generally, both central and gingival salivary gland choristomas appear histologically as encapsulated, lobulated masses composed of normal-appearing salivary gland acini of the mixed type; frequently, mucous acini are prominent, with the usual intermingling of normal ducts. Small to moderate numbers of chronic inflammatory cells such as lymphocytes are commonly observed. The salivary gland choristoma should be differentiated from adenomatous hyperplasia. The latter, by definition, is an increase in the number and size of glands in areas normally occupied by glands. A complication is the development of a cystic lesion or a true salivary gland neoplasm from the salivary gland choristoma. Traeger35 reported a case of a raised mass in the facial aspect of the anterior maxillary gingiva with the histologic appearance of a cyst, lined by a layer of epithelial cells with adjacent salivary gland acini. This case seems to be an example of a choristomatous cyst of salivary gland. Some authors20, 32,36 mentioned that salivary gland tissue entrapped in the bone may undergo neoplastic change. The review of central salivary gland tumors by Palladino et a1.20 made it obvious that these lesions occur more frequently than central nonneoplastic salivary gland tissue. Those neoplasms include mucoepidermoid tumor,37 mixed tumor,20 adenoid cystic carcinoma, and adenocarcinoma.36 Thus the possibility that neoplastic change may evolve from a salivary gland choristoma should be considered. Cartilaginous

choristoma

Many tumorlike masses composed of differentiated cartilage, such as tendons, tendon sheaths, and extraarticular tissues in hands and feet,38 have been reported in the soft tissues. Only a few cases have been reported in the soft tissues of the oral cavity. Our literature search showed 20 reported cases.39-52 All 20 cases involved extraskeletal cartilaginous nodules in the tongue (17 cases),39-49buccal mucosa (2 cases),50y51 and soft palate (1 case).52 The age at diagnosis ranged widely, from 10 to 80 years, with a mean of 47 years. Eleven patients (58%) were female whereas eight (42%) were male; in one case sex was

not specified. Clinically, the masses were increasing in size. Size ranged from less than 1 cm to several centimeters, with the largest reported to be 13 X 10 cm in diameter.53 Occasionally, superficial inflammation of mucosa (probably caused by irritation from biting or pressure of a denture) and dysphagia or dysphonia, caused by the large size of the mass, were present. Histologically, the cartilaginous choristoma is composed of a tumorlike mass of hyaline cartilage surrounded by dense, fibrous connective tissue suggestive of perichondrium, 5o.52 by loose fibrous connective tissue, or occasionally by myxoid tissue suggestive of primitive mesenchyme. The chondrocytes may be small and lying within clearly defined lacunar spaces in the hyaline intercellular substance, or may be large, mature, and lying in the calcified intercellular substance. The cartilage is usually more mature at the center of the mass and less mature at the periphery. 50,5’ Occasionally, chondroblasts are present in the substance of the cartilage, implying active interstitial growth, or in the inner part of the perichondrium, implying active appositional growth. The innocence of these masses is established by the regularity of the cartilage cells and by the mature differentiation of the hyaline matrix. As to the possible origin of this lesion, the theory that it develops from undifferentiated mesenchymal cells is speculative. Its tumorlike expansion may be explained by the process of cartilage formation from multipotential mesenchymal cells with proper stimulation and by its active interstitial and/or appositional growth. The term “chondroma,” commonly used for these concartilaginous masses, 38-Q 45-W 51,52 is somewhat troversial. Our review of reported examples suggests that these masses are nonneoplastic developmental lesions of cartilage rather than neoplasms. Because the pattern of tumorlike growth and abnormal location fit the criteria of choristoma, “cartilaginous choristoma”

is a more appropriate

term. It is impor-

tant to recognize cartilaginous choristoma at the immature stage and to distinguish it from extraskeletal chondrosarcoma.54, 55 The latter often exhibits cellular pleomorphism, including numerous giant cells,56 and a lack of well-differentiated hyaline. Furthermore, it has been considered to arise de novo rather than from a preexisting benign lesion.57 Cartilaginous choristoma may also be distinguished from cartilaginous metaplasia, which usually occurs in the soft tissue beneath ill-fitting dentures and is histologically characterized by chondroid matrix with diffuse calcium deposits and scattered

cartilaginous

cells ar-

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rangedin variousstagesof maturationin singleor

sionalspaces within themassmaycontain bloodves-

clustered foci. These metaplastic lesions are positioned external to the bone. Recurrence in the intraoral cases of cartilaginous choristoma has not been reported. However, some extraoral cases of “chondroma of soft parts” have been reported to recur,38 probably because of incomplete excision. Because the perichondrium and surrounding connective tissue may have the potential to form new cartilage, complete excision, including the surrounding soft tissue, is recommended.

sels lined with endothelium or fibrous tissue, and a few cells that correspond in appearance to osteoclasts 58 The presence of fatty marrow is not uncommon.67 The cause of the osseous choristoma is unknown. The close proximity of these lesions to the foramen cecum suggests a developmental malformation. Several presumptions, such as ossification of branchial arch remnants64 and development of ectopic mesenchymal cells, 69have been proposed. Other suggestions include epignathous formation and a degenerating fibroma undergoing ossification.70 Treatment consists of surgical removal of the lesion. Recurrence or malignant change has not been reported.

Osseous

choristoma

The term “osseous choristoma” was introduced by Krolls et a1.58to describe a tumorlike growth of normal, mature lamellated bone occurring in the soft tissues of the oral cavity. This uncommon lesion is also known as “osteoma mucosae” or “soft tissueosteoma,” and is analogous to the dermal lesion “osteoma cutis.” Since 1913, when Monserrat’s original report appeared, 39 cases have been reported in the English-language literature.58y 60-70 Of 39 cases, 34 (85%) occurred in the posterior dorsum of the tongue near the circumvallate papillae or the foramen cecum.s8’ 60-62,65,66*68 Three (8%) OCcurred in the middle third of the dorsum of the tongue,62-64 one (3%) in the lingual aspect of the alveolar process of the anterior mandible,65 and one (3%) in the left mandibular buccal vestibule.67 Twenty-eight lesions (72%) were present in females and only 11 in males, making the female/male ratio 2.7:1. The youngest patient at diagnosis was an 8-year-old girl, and the oldest was a 73-year-old man; the average age was 30.7 years. However, the reported duration of the lesions ranged from several months to several years. Clinically, the osseous choristoma is described as either a pedunculated or a sessile mass; therefore this lesion should be included in the differential diagnosis of any pedunculated lesion on the dorsum of the posterior third of the tongue. The size ranges from 0.5 to 2 cm in diameter. The lesions are asymptomatic but occasionally cause choking, gagging, nausea, and dysphagia, depending on the size and location. Histologically, the lesions are composed of a well-circumscribed, lamellated mass of dense, vital bone with haversian canals, surrounded by dense fibrous connective tissue and covered with stratified squamous epithelium in the exophytic part of the swelling. Osteocytes may be seen in the lacunae within the bony spherule. Cellular activity of osteoblasts at the periphery of the osseous mass is inconspicuous.63 Occa-

Lingual thyroid choristoma

Tumorlike growth of lingual thyroid tissue has been reported under the terms “lingual thyroid” or “ectopic thyroid tissue.” It is termed “choristoma” here, although still questionable, because its tumorlike manifestation arising from ectopic thyroid tissue differentiates this clinical entity from simple latent ectopic thyroid tissue. The latter is a developmental anomaly consisting of an aggregate, or small scattered islands, of thyroid tissue occurring in the base of the tongue or at any other point along the route of descent of the thyroid primordium. Because of its asymptomatic nature, its incidence is thought to be much higher than that of lingual thyroid choristoma. The fact that lingual thyroid remnants have been found in 10% of 200 routine autopsies71 and in 9.8% of 184 cadaver tongues72 implies that approximately one of every 10 people may have such microscopic lingual remnants of thyroid tissue. On the other hand, the lingual thyroid choristoma is rare. We could not find a single case in our files on 50,000 oral biopsies. By applying strict standards, we collected 49 cases published in the English-language literature since 1962.73-87 All 49 cases met the following criteria: (1) the lesion was a tumorlike mass occurring in the midportion of the tongue between the foramen cecum and the epiglottis, and (2) the diagnosis was confirmed by radioactive iodine methods or by histologic examination. The ages of these 49 patients at the time of diagnosis ranged from 2% to 72 years, with a mean of 23 years. There were two age peaks, at about 10 and 40 years. Thirty-nine cases (80%) were in females and the female/male ratio was 3.9: 1. It must be noted that the female/male ratio of lingual thyroid choristoma discovered clinically was different from that of simple

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latent ectopic thyroid tissue discovered in routine autopsies, which was 9: 11.‘l The lesions of all 49 patients were in the median line of the base of the tongue between the foramen cecum and the epiglottis. They were rounded, hemispheric, and semisoft or firm masses, with the largest measuring 5.0 X 4.0 cm. Often they were lobulated but covered with normal intact mucosa. The symptoms of lingual thyroid choristoma, produced by an increase in size, were protean and ranged from a slight voice change or a feeling of a foreign body in the throat to hemorrhage, dysphagia, dysphonia, and dyspnea. The use of the gamma scanning camera and the scintillation counter has made the recognition of thyroid choristoma relatively simple in most instances, and a biopsy is then unnecessary.‘t, ‘& 78,88-9’ We found that in 42 of the 49 cases (86%), the tumorlike growth mass of lingual thyroid was the only functional thyroid tissue in the body, as determined by thyroid scan techniques. Hypothyroidism is frequently associated with a unique functional lingual thyroid.77y 92 However, hyperthyroidism is rarely associated and has been noted only when functional thyroid tissue was also present in the normal pretracheal area.92-97 Juvenile myxedema or cretinism was present in 10% of patients.96s 98 In a number of autopsy reports on cretins who died early in life of athyrosis, the only thyroid tissue found was at the base of the tongue.99 Biopsies of lingual thyroid choristoma generally reveal embryonic or mature thyroid tissue, or a combination of the two, with an incomplete or poorly defined capsule. The fetal or microfollicular adenomatous pattern is most common and can be misinterpreted as carcinoma. Variable amounts of lymphocytic infiltration are not uncommon. Rarely, epithelial pearl-like formation7i and association with parathyroid tissue7*> 72 have been reported, but with no explanation of how these bizarre findings might have developed.92 When symptoms associated with lingual thyroid choristoma require treatment, radioactive iodine 13 1 or thyroid hormone suppression to reduce the size of the glands is the method of choice and is especially appropriate in patients whose lingual thyroid is the only functional gland. 73,74~8oy83 Occasionally, efforts to transplant lingual thyroid tissue elsewhere in the body have been successful.‘00 Pathologic changes of lingual thyroid choristoma, including cysts and carcinoma, may occur, because any of the diseases that affect the thyroid gland may also involve ectopic thyroid.87* 9’ Carcinoma develop-

ing in lingual thyroid tissue is extremely rare. We reviewed the English-language literature since 1965 and found only three published cases: two in women, both 40 years old, and one in a 12-year-old boy.84, 101,102Th e d’iagnosis of all three cases was follicular carcinoma. For this reason a frozen-section examination of the specimen should be done to rule out carcinoma before implanting the tissue into other parts of the body. Lingual

sebaceous

choristoma

There have been many reports of sebaceous glands occurring in various sites of the oral mucosa, especially on the buccal and labial mucosa, retromolar area, gingiva, and palate. We do not regard sebaceous glands in these locations as ectopic glandular tissue, because they have been reported to occur in more than 80% of the population. lo3 However, there are rare reports of a mass of sebaceous glands in an unusual location, the dorsum of the tongue. About six cases have been reported in this location in the English-language literature, and the term “sebaceous choristoma” was first used for this particular entity by Leider et al.io4 Of six cases of lingual sebaceous choristoma, five were in men and one was in a woman; their ages ranged from 23 to 73 years at diagnosis. Lesions were described in the dorsal midline of the posterior third in the region of the foramen cecum in two casesto4, to5 and of the middle third in one case.lo6 The lesions also occurred at one side of the dorsal midline of the middle third in two cases.‘07 In one of them a central ostium was easily observed, and exploration with a blunt probe proved this to be the opening of a duct that extended in a plane parallel to the dorsum of the tongue as far as the foramen cecum. Clinically, the lesions are described as firm, asymptomatic, dome-shaped masses. Smooth-surfaced areas might be covered by multiple small, round, yellowish aggregates. The lesions range from 0.2 to 2 cm in diameter. White fluid discharge from the ostium of the conic projection on compression of the lesion was seen in two cases.io6glo7 Histologically, the lesions are composed of numerous lobules of weIl-differentiated branching sebaceous glands associated with stratified squamous epitheliurn-lined excretory ducts continuous with typical dorsum epithelium. Occasionally, small patches of lymphoid tissue are seen along the length of the tube.to4 In addition, ductal structures resembling apocrine sweat glands are commonly observed.io4, lo6, lo7 Pilosebaceous parasites, Demodex folliculorum, were reported encysted within sebaceous glands, which was thought to be due to the duc-

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tal communication of the sebaceous glands with the external environment.106 With regard to those lesions which were associated with thyroglossal ductlike structures, Leider et al.‘” and Knapplo suggested that their cases might have arisen from thyroglossal duct remnants. However, Guiducci and Hyman lo5 believed their case represented “ectodermal sequestration” within the tongue during embryogenesis, because of the lack of lymphoid tissue in the vicinity of their lesion. Glial choristoma

Tumorlike masses composed of mature brain tissue and occurring outside the cranial cavity are distinctly uncommon. Of the recorded cases in the English-language literature, most have been located in and around the nose,108-110 nasopharynx,“** lt2 eye,l13 orbit,l14 and lung. 1l5 For these masses to occur in the oral cavity with no connection to the central nervous system is extremely rare. To date, a total of 13 cases have been reported within the oral cavity. The terminology for a mature brain tissue mass in the oral cavity is controversial. The terms most often used are “heterotopic brain tissue”’ 14,116-lz4 and “extracranial glioma. “125, 126 After reevaluating the reported cases, we question the suitability of these terms. “Heterotopic brain tissue” implies that the brain tissue is ectopic but does not reflect the fact that the ectopic tissue grows as a tumorlike mass. In addition, the mature appearance of the glial elements, with differentiated specialized structures, and the lack of either continued growth or invasive patterns of the lesional tissue indicate that these masses are not neoplasms. Thus the term “glioma” is inappropriate. Furthermore, the mass cannot be classified as a teratoma, because no mesodermal or endodermal elements were identified. In our opinion, in recognition of the distinction between tumorlike growth and simply ectopic tissue, and between normal tissue growth and true neoplasia, “glial choristoma” is a more appropriate term. Clinically, all 13 cases (10 in female patients) presented as a raised, large, firm mass covered by normal oral mucosa. In seven cases lesions were located in the soft palate, frequently extending forward to the hard palate and/or backward to the oropharynx. The largest mass, measuring 6.0 X 6.0 X 5.0 cm in diameter, was reported in a newborn girl.120 Of those cases in the palatal region, two were associated with partial cleft palate and the lesions were in one side of the soft palate.*17, It9 Formation of a partial palatal cleft was suggested to result from mechanical obstruction of growth of the maxillary process by “a severed rem-

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nant of brain.“l12 Other locations of lesions are the cheek extending from the preauricular region to the submandibular area (two casesj,123, 124 the anterior two thirds of the dorsum of the tongue (two cases), 125~126and the oropharynx, extending upward into the nasopharynx (two cases).121,122 Most patients have lesions between 3.0 and 5.0 cm in diameter before 1 year of age, at which time surgical excision is usually performed. A possible explanation for this rapid growth in infants is that the glial choristoma could grow as rapidly as does normal brain tissue during infancy.127 Histologically, the encapsulated -mass&s are composed of mature central nervous tissue elements, with rather wide variation in the amounts of connective tissue present. Astrocytes are commonly identifiable within masses of glial fibers, a finding that was confirmed by immunocytochemical and ultrastructural studies.125 In some cases cleftlike spaces are lined by mature ependymal cells, and in some areas the lining cells form papillary projections, suggesting differentiation into choroid plexus.’ 1‘p 117-12’*126Occasionally some unusual components .are seen, such as spongioblasts,126 oligodendrocytes,121y lz6 and ganglion cells.1163119 Abnormal mitoses, nuclear hyperchromatism, or prominent nucleoli are not noted. Macomber .and Wang*** proposed that glial choristoma is caused by separation of ceils from the anterior part of the brain in early embryonal development. Shapiro and Mix117 and Kurzer et a1.125 considered that the lesion develops from a misplaced primordium. This latter theory might better explain those lesions occurring in the oral cavity. Surgical excision is suggested for glial choristoma. Recurrence, as a result of incomplete excision because of technical difficulties in determining the lesion’s extent, is rare. Gastric mucosal choristoma

The oral lesion containing .heterotopic gastric elements was first described in 1927 by Toyama12g as “stomach mucosa at base of tongue.” We term this lesion “gastric mucosal choristoma” because of its abnormal location and innocent tumorlike growth. Since 1960 a total of 21 cases of intraoral gastric mucosal choristoma have been reported.r30-147 A careful evaluation of these cases revealed that all but two146*147presented as a cyst within the oral cavity. Therefore gastric mucosal choristoma may be subclassified as cystic or solid entities. Gastric cystic choristoma. This entity is defined as a cystic lesion in the oral cavity, that is usually lined partly by stratified squamous epithelium and partly

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by gastric mucosa, and occasionally by intestinal epithelium. Of 19 reported cases, 12 (63%) occurred in the ventral surface of the tongue and usually extended to the floor of the mouth,‘33% ‘37-‘43s ‘45 four (21%) occurred in the anterior third of the tongue,‘3’, ‘35, ‘44 and three (18%) were in the mid-dorsum of the tongue.‘3’, 134.‘36 T we 1ve 1esions (63%) were present in males, and seven in females. The lesions generally occurred during infancy or early childhood, and many were left untreated for considerable periods of time. The age of patients at the time of diagnosis ranged from newborn to 31 years. The lesions usually present as asymptomatic swellings, ranging in size from 1 to 3 cm in diameter. The cyst walls are relatively thick, and the internal surfaces are slightly granular and congested. Multiple cysts in the anterior portion of the floor of the mouth were reported in one male infant.‘33 Microscopically, the lining of these lesions is that of the cardiac, fundus, or pylorus regions of the stomach. In addition to gastric epithelium, these cysts sometimes show other types of mucosal lining such as stratified squamous, simple columnar, and ciliated columnar epithelium. Usually, the well-defined smooth muscle layer is seen outside the mucosal layer. In one case14’ the cyst communicated with the surface of the tongue by an orifice lined by stratified squamous epithelium. Heterotopic gastric mucosa has been postulated to arise from misplaced embryonal gastric rests, because in the 3 to 4 mm embryo (4 weeks) the undifferentiated primitive stomach lies in the midneck region close to the primordium of the tongue. It has been assumed that the endodermal gastric mucosa becomes entrapped in the midline of the tongue by fusion of the lateral lingual swellings over the tuberculum impar. Various features of these cysts, such as the presence of parietal, chief, and mucous neck cells, and closely associated smooth fibers, indicate a high degree of differentiation and organization. Lectins have been used for histochemical studies on mucin in intraoral gastric cystic choristoma. ‘42 The presence of galactose, IV-acetylgalactosamine, and galactose N-acetylgalactosamine structures favor the view that these lesions arise from undifferentiated endoderm subjected to an inductive influence; this results in various degrees of differentiation, thus explaining the rather variable resemblance of this lesion to gastric, intestinal, or colonic mucosa. Conservative excision is the treatment of choice; of the patients reviewed, only one patient required a second excision, as a result of incomplete removal originally. Solidgastric mucosal choristoma. In 1972 Gruskin

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and Landolfe’46 reported a 2.0 X 1.5 X 1.5 cm polypoid mass on the dorsum of the tongue, at the junction of the anterior third and posterior two thirds, in a 20-year-old man. The lesion had been present since birth and had been excised 14 years previously but had slowly recurred. This recurrent mass was excised, and microscopic examination showed that the major portion was composed of mucosa almost identical to that found in the fundus and body of the normal stomach. The surface of the mass was covered by a mucin-secreting simple columnar epithelium that Ied into gastric pits and glands. The glands contained cells that were indistinguishable from normal parietal cells, chief cells, and mucous neck cells. Beneath the glands were several discontinuous layers of smooth muscle bundles that formed a muscular mucosae. Wurster et al.‘47 in 1985 reported a polypoid mass, 2.0 cm in diameter, on the dorsum of the anterior aspect of the tongue of a 30-year-old woman. The lesion had been present for 9 months and interfered with articulation. Examination of the excisional biopsy speci’nen satisfied all the criteria for the identification of gastric mucosa except that chief and parietal cells were lacking. The presence of primordial mucous glands and the layer of smooth muscle leave no doubt as to its gastric nature. An IS-month follow-up revealed no recurrence of the mass. These two cases were the only English-language reports of a solid mass of heterotopic gastric mucosa in the oral cavity. Because the findings in these examples consisted of a tumorlike mass clinically and ectopic gastric mucosa microscopically, we believe, at least for the present, that the designation “solid gastric mucosal choristoma,” as distinguished from the cystic lesion, is appropriate. We thank Evangeline

Leash for editing the manuscript.

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6. Arwill T, Heyden G. Ramstedt A. Follicular choristoma 01 the gingiva: a peculiar lesion. ORAL SURF ORAL MED ORAL PATHOL

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7. Blaney TD, Bellizzi R, Hartwell GR. Presentation of skeletal muscle tissue in an unusual location: a case report. J Endod 1982;8:421-3. placed parotid gland tn the mandible. 8. Slavin MI. Ectopically ORAL

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Louis S. Hansen, DDS, MS, MB Division of Oral Pathology University of California San Francisco, CA 94143-0424