Prog. expo Tumor Res., vol. 20, pp. 195-204 (Karger, Basel 1976)
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni c.J.
DAWE, R. SONSTEGARD, M.F. STANTON, D.E. WORONECKI and R. T. REPPERT
Laboratory of Pathology, National Cancer Institute" National Institutes of Health, Bethesda, Md.; Department of Microbiology, College of Biological Science, University of Guelph, Ont.; Cold Water Fishery Section, Albert M. Powell State Fish Hatchery, Hagerstown, Md.; Department of the Army, Corps of Engineers, Board of Engineers for Rivers and Harbors, Washington, D.C.
Intrahepatic biliary duct neoplasms were discovered in 1963 in Catastomus commersoni (white suckers) taken from Deep Creek Lake, Maryland [3]. As 3 such tumors were found among only 12 fish of this species examined, it was at first supposed that these tumors might be species-associated through a direct genetic influence, or that they might be indicative of some highly carcinogenic environmental factor(s) to which the fish of this species were selectively exposed. This brief communication is a report of a continued search for similar tumors in C. commersoni taken from widely separated aquatic environments over a lO-year period.
Materials and Methods
36
C.l.D. and M.F.S.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Table I indicates the methods of fish capture, the waters from which fish were taken, and the dates of capture. Sex was recorded in only some of the samples, as indicated. Since the smallest fish in which an hepatic tumor was found measured 15 inches in length, this length was chosen as a reference point for comparability of sampling in the parameter of body size. Four capture methods were used: rotenone poisoning, gill nets, pond drainage followed by hand capture, and electroshock. The majority were taken by gill net. Gross examination of the fish for liver tumors was necessarily done under variable conditions: (I) in the field immediately after killing the fish; (2) in the laboratory within
DAwEetal.
196
Table I Vicinity of
Deep Creek Lake Antietam Creek Spring Creek Isaac Walton Pond Patuxent River
McHenry, Md.
Method of capture
Numberof fish collected
9/4/63
rotenone
12
5
Hagerstown, Md.
2/18/64
20
0
Bellefonte, Pa.
3/18/64
68
13
Poolesville, Md.
9/19/64
electroshock e1ectroshock pond drainage gill net
6
4
18
15
6
4
17
15
24
2
Tridelphia Res., Md.
Date captured
5/1/64
Num- Sex berof fish >15 in
Deep Creek McHenry, Md. Lake Pleasant Valley Bittinger, Md. Lake Beaver Creek Hagerstown, Md.
12/9/64
gill net
12/9/64
Choptank River Greensboro, Md. Piney Creek Carroll Co., Md.
4/13/71 7/7/71
2 2
2 0
Deep Creek Lake Deep Creek Lake Deep Creek Lake Moose River Cold Lake Lake Simcoe Ostego Lake Houghton Lake
McHenry, Md.
4/14/72
lake drainage electroshock gill net electroshock gill net
16
14
McHenry, Md.
4/12/73
gill net
30
30
McHenry, Md.
4/5/74
gill net
22
18
Moosonee, Onto Grand Centre, Alb. Beaverton, Onto Gaylord, Mich. Houghton Lake, Mich. St.Lawrence R. Montreal, Que. Lake Ontario Toronto, Onto Lake Ontario Hamilton, Onto Lake Ontario Jordan Harbor, Onto Lake Ontario Rochester, N.Y. Buffalo, N.Y. Lake Erie Port Rowan, Onto Lake Erie
9/1/70
Number of tumors
2NS 3 1 Cf 12 Cf 0 8352Cf 0 166 0 Cf 11 Cf 53- 0 2NS 6Cf 0 8Cf 9318 Cf 66 NS 1 Cf 13NS
8/3/72 7/10/70 5/6/73 4/18/74 4/19/74
gill gill gill gill gill
net net net net net
40 200 550 23 17
40 200 550 23 17
18 Cf 1237Cf 153NS NS NS NS NS
4/25/74 5/26/74 5/3/74 5/25/74 5/17/74 5/14/74 4/28/73
gill gill gill gill gill gill gill
net net net net net net net
54 159 464 38 49 6 22
54 159 464 38 49 6 22
NS NS NS NS NS NS NS
130 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0
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Body of water
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni
197
Table I (continued)
Body of water
Vicinity of
Date captured
Method of capture
Number of fish collected
Num- Sex berof fish >15in
Number of tumors
Lake Erie Lake Erie Lake Erie Lake Huron Lake Huron Lake Huron Lake Huron Lake Huron Lake Huron Lake Huron Lake Michigan Lake Michigan Lake Superior Lake Superior
Detroit, Mich. Cleveland, Ohio Toledo, Ohio Sarina, Onto Kincardine, Ont. Southampton, Ont. Parry Sound, Ont. Byng Inlet, Ont. Little Current, Ont. Bay City, Mich. E. Chicago, Ind. Milwaukee, Wisc. Duluth, Minn. Thunder Bay, Onto
5/28/74 6/3/74 6/1/74 7/27/74 6/29/74 6/26/74 6/16/74 6/20/74 6/23/74 7/11/74 7/15/74 7/19/74 7/22/74 7/26/74
gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net
3 3 4 200 107 132 167 52 140 51 11 51 33 406
3 3 4 200 107 132 167 52 140 51 11 51 33 406
0 0 0 0 0 0 0 0 0 0 0 0 0 0
NS NS NS NS NS NS NS NS NS NS NS NS NS NS
24 hours of transport of fish on ice; (3) in the laboratory following formalin fixation of the viscera in the field. Each of the 4 neoplasms in table I was histologically confirmed by examination of hematoxylin-eosin-stained sections. Any areas of liver showing unusual color characteristics or deviations from normal consistency were examined histologically, but all of the confirmed cholangial neoplasms were actually first recognized during gross examination. Regaud's iron hematoxylin method was applied to tumor and normal liver for identification of protozoan parasites.
As indicated in table I, only a single additional tumor of biliary duct origin was found among 3,208 fish examined in collections subsequent to that of 1963, and that example was found in a fish taken in 1964 from a small lake (Pleasant Valley Lake) within 5 miles of Deep Creek Lake, having a similar watershed. Pleasant Valley Lake had been specifically selected for sampling because of its proximity to Deep Creek Lake and because no motorboating had been permitted on Pleasant Valley Lake for many years. Residues from engine exhausts had been postulated [3] as one factor possibly related etiologically to these neoplasms.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Results
DAWE
et al.
198
Although 66 C. commersoni measuring over 15 inches in length were taken from Deep Creek Lake subsequent to 1963, none was found to bear a liver tumor. It may be relevant to note that the method of capture of all fish from Deep Creek Lake subsequent to 1963 was by gill net, whereas the fish collected in 1963 were taken by rotenone poisoning. The tumor-bearing fish from Pleasant Valley Lake was a male measuring 15 inches in length. This represents the smallest specimen in which a bile duct tumor has yet been found. The three tumor-bearing fish from Deep Creek Lake in 1963 all measured more than 20 inches. All of the tumorbearing fish were therefore at least 5 years old and some may have been 15 or more years old according to data collected by BEAMISH [2]. Among the total of 103 fish examined from the two bodies of water where the tumors have been found, 17 were less than 15 inches and 86 were 15 inches or more in length. Of 3,105 fish from other waters, only 102 were smaller than 15 inches.
The single tumor-bearing specimen obtained after the 1963 report was a male with fork-length of 15 inches. It was well nourished, with no visible external sign of the neoplasm or other disease. It had been captured by hand after drainage of the lake, and was examined after the entire fish, with body cavity open, had been fixed in 10% formalin for several days. One lobe of the liver contained a firm, discrete mass 2.5 cm in diameter, umbilicated on its serosal surface. This mass was much firmer than the liver surrounding it, and its cut surface was gray and slightly raised above the adjacent yellow-brown liver. No gross evidence of tumor in other organs was found. Histologically, th~ tumor was closely similar to the three previously studied from Deep Creek Lake. It was composed of closely grouped, irregularly shaped duct-like structures lined by columnar epithelium much like that of normal intrahepatic biliary ducts (fig. I). The neoplastic epithelial cells were fairly uniform in size and nuclear characteristics, although nuclei tended to be located at variable levels relative to the basal poles of the cells. Mitoses were moderately numerous. The stroma was variable, in some areas being composed of copious amounts of loose fibrous tissue surrounding groups of the neoplastic duct-like structures. Centrally, there were foci of necrosis. Peripherally, the tumor was unencapsulated, and single duct-like structures or groups of them extended into adjacent liver parenchyma.
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Pathology
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni
199
Search revealed, between the epithelial cells of the tumor, occasional thick-walled, rodlet-containing cells (fig. 2) of the same type previously described in the three tumors from Deep Creek Lake [2]. These have been variably thought to be: (a) protozoan parasites designated Rhabdospora thelohani (Laguesse) [1]; (b) specialized gland cells [5]; or (c) a special type of leukocyte peculiar to some fishes [4]. BANNISTER'S [1] ultrastructural study of these cells provides the strongest available evidence in favor of their parasitic nature.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Fig. 1. Cholangioma in the specimen taken from Pleasant Valley Lake in 1964. Tumor is composed of closely grouped, biliary duct-like structures lying within a cellular, fibrous stroma. Normal liver to right of unencapsulated tumor margin. HE. x 90.
DAWE
et al.
200
Fig. 2. A rod let cell (Rhabdospora thelomani) lying (short arrow) among neoplastic epithelial cells of the tumor. Long arrow indicates a tumor cell in late telophase of mitosis. HE. x 475.
presence of the above parasite (or rodlet cell) between the epithelial cells of bile ducts. Occasionally we have encountered small proliferations of biliary duct epithelium containing large numbers of this parasite-like cell (fig. 3 and 4). These proliferative lesions, though not manifestly neoplastic, might conceivably represent incipient tumors or pre neoplastic changes in bile duct epithelium reacting to the presence of the parasite.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Histological examination of nontumor-containing livers from C. commersoni has, in nearly every individual we have examined, revealed the
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni
201
Fig. 3. A focus of hyperplasia of interlobular biliary ducts in a nontumor-bearing fish. HE. x 140.
Contrary to expectations based on the small 1963 sampling from Deep Creek Lake [3], this rather extensive survey of C. commersoni from many environments, including Deep Creek Lake, has yielded only a single additional example of intrahepatic biliary duct tumor. This additional example came from a small lake close to Deep Creek Lake, and was found only a little more than a year after the first 3 tumors were discovered in fish from Deep Creek Lake.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Discussion
DAwEetal.
202
The paucity of positive findings warns against attempting a precise interpretation. The tumor in a fish from a lake other than Deep Creek Lake does establish that fish with such tumors are not limited to Deep Creek Lake, but Pleasant Valley Lake is so close to Deep Creek Lake that it might be presumed the two environments are essentially the same. This is not true with respect to one variable, however: the effects that motorboating might have in introducing products of internal combustion engines into the waters and bottom sediments. Since Pleasant Valley Lake has no motorboat activities,
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Fig. 4. Higher magnification of a portion of the field in figure 3, showing (arrows) numerous rodlet cells (Rhabdospora thelomani) among the epithelial cells lining the bile ducts. HE. x 350.
203
it seems unlikely that the hepatic neoplasms are related to pollution from motorboats. The failure to find biliary duct neoplasms in C. commersoni from many widely separated waters in the eastern and mid-western US and Canada does not necessarily mean that the neoplasms do not occur in the locations surveyed. Because of legal restrictions and the characteristics of most of the habitats sampled, different methods of capture were used in localities other than Pleasant Valley Lake and Deep Creek Lake. While fish from the latter sites were taken by water drainage and by rotenone poisoning, respectively, most of those taken elsewhere were caught by gill nets placed in appropriate locations during spawning runs. This difference could have a decidedly selective effect on the sampling. For example, if fish bearing the neoplasms do not take part in the spawning runs, they obviously would not be caught by gill-netting the spawners. This consideration might well be relevant, since several of the fish in the original sample taken by rotenone from Deep Creek Lake were found to have retained ova from the preceding season. Fish carrying old, retained ova have rarely, if ever, been found in an active spawning run. The apparent ubiquity of the parasite found in the tumors makes it difficult to assess the possible influence of this parasite on the development of the tumors. Perhaps the continued presence of the parasite in bile duct epithelium leads to tumor development in some proportion of older fish. This hypothesis is consistent with the observation that only large fish in an age group of 5 to more than 15 years have been found with this type of tumor. It is also consistent with the observation that proliferative, but nonneoplastic, lesions of bile duct epithelium have been seen to contain large numbers of the parasite. Unfortunately, it is also reasonable to postulate that hyperplastic duct epithelium as well as neoplastic duct epithelium provides a more ideal habitat for the parasites than does normal bile duct epithelium. The present survey throws no light on the question as to whether insecticides, herbicides, or chemical contaminants of any type in the environment have any causal influence on the occurrence of these tumors. More than anything, perhaps, the results of the survey reflect the problems inherent to epizootiologic studies involving the application of different methods of sampling to different fish populations in different habitats under different seasonal conditions. Only where these variables can be controlled will it be practical to assign quantitative significance to data regarding the prevalence of neoplasms in feral fishes.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni
DAwEetal.
204
Summary
In 1963, intrahepatic cholangial neoplasms were found in 3 of 12 white suckers (Catastomus commersoni) taken from Deep Creek Lake, Maryland. A subsequent survey covering a 10-year period has yielded only 1 additional tumor of the same type from a collection of 3,208 fish of the same species. The single additional neoplasm was in a fish from Pleasant Valley Lake, located only a few miles from Deep Creek Lake. Cells of disputed parasitic nature (Rhabdospora thelohani) were found in all 4 of the cholangial neoplasms, but were also found in the biliary duct epithelium of livers without tumors. The etiology of the tumors remains unknown.
References 2 2
3
BANNISTER, L. H.: Is Rhabdospora thelohani (Laguesse) a sporozoan parasite or a tissue cell of lower vertebrates? Parasitology 56: 633-638 (1966). BEAMISH, R. J.: Factors affecting the age and size of the white sucker, Catastomlls commersoni at maturity. Thesis cited by SCOTT and CROSSMAN; in Freshwater fishes of Canada, Bulletin 184, p. 541 (Fisheries Research Board of Canada, Ottawa 1973). DAWE, c.J.; STANTON, M.F., and SCHWARTZ, F.J.: Hepatic neoplasms in native bottom-feeding fish of Deep Creek Lake, Maryland. Cancer Res. 24: 1194-1201 (1964).
5
DUTHIE, E. S.: The origin, development, and function of the blood cells in certain marine teleosts. 1. Morphology. J. Anat. 73: 396-412 (1939). PLEHN, M.: Driisenzellen oder Parasiten? Anat. Anz. 29: 152-156 (1906).
C. J. DAWE, MD, Laboratory of Pathology, National Cancer Institute, National Institute of Health, Bethesda, MD. 20014 (USA)
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4
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni c.J.
DAWE, R. SONSTEGARD, M.F. STANTON, D.E. WORONECKI and R. T. REPPERT
Laboratory of Pathology, National Cancer Institute" National Institutes of Health, Bethesda, Md.; Department of Microbiology, College of Biological Science, University of Guelph, Ont.; Cold Water Fishery Section, Albert M. Powell State Fish Hatchery, Hagerstown, Md.; Department of the Army, Corps of Engineers, Board of Engineers for Rivers and Harbors, Washington, D.C.
Intrahepatic biliary duct neoplasms were discovered in 1963 in Catastomus commersoni (white suckers) taken from Deep Creek Lake, Maryland [3]. As 3 such tumors were found among only 12 fish of this species examined, it was at first supposed that these tumors might be species-associated through a direct genetic influence, or that they might be indicative of some highly carcinogenic environmental factor(s) to which the fish of this species were selectively exposed. This brief communication is a report of a continued search for similar tumors in C. commersoni taken from widely separated aquatic environments over a lO-year period.
Materials and Methods
36
C.l.D. and M.F.S.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Table I indicates the methods of fish capture, the waters from which fish were taken, and the dates of capture. Sex was recorded in only some of the samples, as indicated. Since the smallest fish in which an hepatic tumor was found measured 15 inches in length, this length was chosen as a reference point for comparability of sampling in the parameter of body size. Four capture methods were used: rotenone poisoning, gill nets, pond drainage followed by hand capture, and electroshock. The majority were taken by gill net. Gross examination of the fish for liver tumors was necessarily done under variable conditions: (I) in the field immediately after killing the fish; (2) in the laboratory within
DAwEetal.
196
Table I Vicinity of
Deep Creek Lake Antietam Creek Spring Creek Isaac Walton Pond Patuxent River
McHenry, Md.
Method of capture
Numberof fish collected
9/4/63
rotenone
12
5
Hagerstown, Md.
2/18/64
20
0
Bellefonte, Pa.
3/18/64
68
13
Poolesville, Md.
9/19/64
electroshock e1ectroshock pond drainage gill net
6
4
18
15
6
4
17
15
24
2
Tridelphia Res., Md.
Date captured
5/1/64
Num- Sex berof fish >15 in
Deep Creek McHenry, Md. Lake Pleasant Valley Bittinger, Md. Lake Beaver Creek Hagerstown, Md.
12/9/64
gill net
12/9/64
Choptank River Greensboro, Md. Piney Creek Carroll Co., Md.
4/13/71 7/7/71
2 2
2 0
Deep Creek Lake Deep Creek Lake Deep Creek Lake Moose River Cold Lake Lake Simcoe Ostego Lake Houghton Lake
McHenry, Md.
4/14/72
lake drainage electroshock gill net electroshock gill net
16
14
McHenry, Md.
4/12/73
gill net
30
30
McHenry, Md.
4/5/74
gill net
22
18
Moosonee, Onto Grand Centre, Alb. Beaverton, Onto Gaylord, Mich. Houghton Lake, Mich. St.Lawrence R. Montreal, Que. Lake Ontario Toronto, Onto Lake Ontario Hamilton, Onto Lake Ontario Jordan Harbor, Onto Lake Ontario Rochester, N.Y. Buffalo, N.Y. Lake Erie Port Rowan, Onto Lake Erie
9/1/70
Number of tumors
2NS 3 1 Cf 12 Cf 0 8352Cf 0 166 0 Cf 11 Cf 53- 0 2NS 6Cf 0 8Cf 9318 Cf 66 NS 1 Cf 13NS
8/3/72 7/10/70 5/6/73 4/18/74 4/19/74
gill gill gill gill gill
net net net net net
40 200 550 23 17
40 200 550 23 17
18 Cf 1237Cf 153NS NS NS NS NS
4/25/74 5/26/74 5/3/74 5/25/74 5/17/74 5/14/74 4/28/73
gill gill gill gill gill gill gill
net net net net net net net
54 159 464 38 49 6 22
54 159 464 38 49 6 22
NS NS NS NS NS NS NS
130 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0
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Body of water
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni
197
Table I (continued)
Body of water
Vicinity of
Date captured
Method of capture
Number of fish collected
Num- Sex berof fish >15in
Number of tumors
Lake Erie Lake Erie Lake Erie Lake Huron Lake Huron Lake Huron Lake Huron Lake Huron Lake Huron Lake Huron Lake Michigan Lake Michigan Lake Superior Lake Superior
Detroit, Mich. Cleveland, Ohio Toledo, Ohio Sarina, Onto Kincardine, Ont. Southampton, Ont. Parry Sound, Ont. Byng Inlet, Ont. Little Current, Ont. Bay City, Mich. E. Chicago, Ind. Milwaukee, Wisc. Duluth, Minn. Thunder Bay, Onto
5/28/74 6/3/74 6/1/74 7/27/74 6/29/74 6/26/74 6/16/74 6/20/74 6/23/74 7/11/74 7/15/74 7/19/74 7/22/74 7/26/74
gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net gill net
3 3 4 200 107 132 167 52 140 51 11 51 33 406
3 3 4 200 107 132 167 52 140 51 11 51 33 406
0 0 0 0 0 0 0 0 0 0 0 0 0 0
NS NS NS NS NS NS NS NS NS NS NS NS NS NS
24 hours of transport of fish on ice; (3) in the laboratory following formalin fixation of the viscera in the field. Each of the 4 neoplasms in table I was histologically confirmed by examination of hematoxylin-eosin-stained sections. Any areas of liver showing unusual color characteristics or deviations from normal consistency were examined histologically, but all of the confirmed cholangial neoplasms were actually first recognized during gross examination. Regaud's iron hematoxylin method was applied to tumor and normal liver for identification of protozoan parasites.
As indicated in table I, only a single additional tumor of biliary duct origin was found among 3,208 fish examined in collections subsequent to that of 1963, and that example was found in a fish taken in 1964 from a small lake (Pleasant Valley Lake) within 5 miles of Deep Creek Lake, having a similar watershed. Pleasant Valley Lake had been specifically selected for sampling because of its proximity to Deep Creek Lake and because no motorboating had been permitted on Pleasant Valley Lake for many years. Residues from engine exhausts had been postulated [3] as one factor possibly related etiologically to these neoplasms.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Results
DAWE
et al.
198
Although 66 C. commersoni measuring over 15 inches in length were taken from Deep Creek Lake subsequent to 1963, none was found to bear a liver tumor. It may be relevant to note that the method of capture of all fish from Deep Creek Lake subsequent to 1963 was by gill net, whereas the fish collected in 1963 were taken by rotenone poisoning. The tumor-bearing fish from Pleasant Valley Lake was a male measuring 15 inches in length. This represents the smallest specimen in which a bile duct tumor has yet been found. The three tumor-bearing fish from Deep Creek Lake in 1963 all measured more than 20 inches. All of the tumorbearing fish were therefore at least 5 years old and some may have been 15 or more years old according to data collected by BEAMISH [2]. Among the total of 103 fish examined from the two bodies of water where the tumors have been found, 17 were less than 15 inches and 86 were 15 inches or more in length. Of 3,105 fish from other waters, only 102 were smaller than 15 inches.
The single tumor-bearing specimen obtained after the 1963 report was a male with fork-length of 15 inches. It was well nourished, with no visible external sign of the neoplasm or other disease. It had been captured by hand after drainage of the lake, and was examined after the entire fish, with body cavity open, had been fixed in 10% formalin for several days. One lobe of the liver contained a firm, discrete mass 2.5 cm in diameter, umbilicated on its serosal surface. This mass was much firmer than the liver surrounding it, and its cut surface was gray and slightly raised above the adjacent yellow-brown liver. No gross evidence of tumor in other organs was found. Histologically, th~ tumor was closely similar to the three previously studied from Deep Creek Lake. It was composed of closely grouped, irregularly shaped duct-like structures lined by columnar epithelium much like that of normal intrahepatic biliary ducts (fig. I). The neoplastic epithelial cells were fairly uniform in size and nuclear characteristics, although nuclei tended to be located at variable levels relative to the basal poles of the cells. Mitoses were moderately numerous. The stroma was variable, in some areas being composed of copious amounts of loose fibrous tissue surrounding groups of the neoplastic duct-like structures. Centrally, there were foci of necrosis. Peripherally, the tumor was unencapsulated, and single duct-like structures or groups of them extended into adjacent liver parenchyma.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Pathology
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni
199
Search revealed, between the epithelial cells of the tumor, occasional thick-walled, rodlet-containing cells (fig. 2) of the same type previously described in the three tumors from Deep Creek Lake [2]. These have been variably thought to be: (a) protozoan parasites designated Rhabdospora thelohani (Laguesse) [1]; (b) specialized gland cells [5]; or (c) a special type of leukocyte peculiar to some fishes [4]. BANNISTER'S [1] ultrastructural study of these cells provides the strongest available evidence in favor of their parasitic nature.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Fig. 1. Cholangioma in the specimen taken from Pleasant Valley Lake in 1964. Tumor is composed of closely grouped, biliary duct-like structures lying within a cellular, fibrous stroma. Normal liver to right of unencapsulated tumor margin. HE. x 90.
DAWE
et al.
200
Fig. 2. A rod let cell (Rhabdospora thelomani) lying (short arrow) among neoplastic epithelial cells of the tumor. Long arrow indicates a tumor cell in late telophase of mitosis. HE. x 475.
presence of the above parasite (or rodlet cell) between the epithelial cells of bile ducts. Occasionally we have encountered small proliferations of biliary duct epithelium containing large numbers of this parasite-like cell (fig. 3 and 4). These proliferative lesions, though not manifestly neoplastic, might conceivably represent incipient tumors or pre neoplastic changes in bile duct epithelium reacting to the presence of the parasite.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Histological examination of nontumor-containing livers from C. commersoni has, in nearly every individual we have examined, revealed the
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni
201
Fig. 3. A focus of hyperplasia of interlobular biliary ducts in a nontumor-bearing fish. HE. x 140.
Contrary to expectations based on the small 1963 sampling from Deep Creek Lake [3], this rather extensive survey of C. commersoni from many environments, including Deep Creek Lake, has yielded only a single additional example of intrahepatic biliary duct tumor. This additional example came from a small lake close to Deep Creek Lake, and was found only a little more than a year after the first 3 tumors were discovered in fish from Deep Creek Lake.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Discussion
DAwEetal.
202
The paucity of positive findings warns against attempting a precise interpretation. The tumor in a fish from a lake other than Deep Creek Lake does establish that fish with such tumors are not limited to Deep Creek Lake, but Pleasant Valley Lake is so close to Deep Creek Lake that it might be presumed the two environments are essentially the same. This is not true with respect to one variable, however: the effects that motorboating might have in introducing products of internal combustion engines into the waters and bottom sediments. Since Pleasant Valley Lake has no motorboat activities,
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Fig. 4. Higher magnification of a portion of the field in figure 3, showing (arrows) numerous rodlet cells (Rhabdospora thelomani) among the epithelial cells lining the bile ducts. HE. x 350.
203
it seems unlikely that the hepatic neoplasms are related to pollution from motorboats. The failure to find biliary duct neoplasms in C. commersoni from many widely separated waters in the eastern and mid-western US and Canada does not necessarily mean that the neoplasms do not occur in the locations surveyed. Because of legal restrictions and the characteristics of most of the habitats sampled, different methods of capture were used in localities other than Pleasant Valley Lake and Deep Creek Lake. While fish from the latter sites were taken by water drainage and by rotenone poisoning, respectively, most of those taken elsewhere were caught by gill nets placed in appropriate locations during spawning runs. This difference could have a decidedly selective effect on the sampling. For example, if fish bearing the neoplasms do not take part in the spawning runs, they obviously would not be caught by gill-netting the spawners. This consideration might well be relevant, since several of the fish in the original sample taken by rotenone from Deep Creek Lake were found to have retained ova from the preceding season. Fish carrying old, retained ova have rarely, if ever, been found in an active spawning run. The apparent ubiquity of the parasite found in the tumors makes it difficult to assess the possible influence of this parasite on the development of the tumors. Perhaps the continued presence of the parasite in bile duct epithelium leads to tumor development in some proportion of older fish. This hypothesis is consistent with the observation that only large fish in an age group of 5 to more than 15 years have been found with this type of tumor. It is also consistent with the observation that proliferative, but nonneoplastic, lesions of bile duct epithelium have been seen to contain large numbers of the parasite. Unfortunately, it is also reasonable to postulate that hyperplastic duct epithelium as well as neoplastic duct epithelium provides a more ideal habitat for the parasites than does normal bile duct epithelium. The present survey throws no light on the question as to whether insecticides, herbicides, or chemical contaminants of any type in the environment have any causal influence on the occurrence of these tumors. More than anything, perhaps, the results of the survey reflect the problems inherent to epizootiologic studies involving the application of different methods of sampling to different fish populations in different habitats under different seasonal conditions. Only where these variables can be controlled will it be practical to assign quantitative significance to data regarding the prevalence of neoplasms in feral fishes.
Downloaded by: Université de Paris 193.51.85.197 - 1/18/2020 1:15:47 AM
Intrahepatic Biliary Duct Neoplasms in Catastomus commersoni
DAwEetal.
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Summary
In 1963, intrahepatic cholangial neoplasms were found in 3 of 12 white suckers (Catastomus commersoni) taken from Deep Creek Lake, Maryland. A subsequent survey covering a 10-year period has yielded only 1 additional tumor of the same type from a collection of 3,208 fish of the same species. The single additional neoplasm was in a fish from Pleasant Valley Lake, located only a few miles from Deep Creek Lake. Cells of disputed parasitic nature (Rhabdospora thelohani) were found in all 4 of the cholangial neoplasms, but were also found in the biliary duct epithelium of livers without tumors. The etiology of the tumors remains unknown.
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BANNISTER, L. H.: Is Rhabdospora thelohani (Laguesse) a sporozoan parasite or a tissue cell of lower vertebrates? Parasitology 56: 633-638 (1966). BEAMISH, R. J.: Factors affecting the age and size of the white sucker, Catastomlls commersoni at maturity. Thesis cited by SCOTT and CROSSMAN; in Freshwater fishes of Canada, Bulletin 184, p. 541 (Fisheries Research Board of Canada, Ottawa 1973). DAWE, c.J.; STANTON, M.F., and SCHWARTZ, F.J.: Hepatic neoplasms in native bottom-feeding fish of Deep Creek Lake, Maryland. Cancer Res. 24: 1194-1201 (1964).
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DUTHIE, E. S.: The origin, development, and function of the blood cells in certain marine teleosts. 1. Morphology. J. Anat. 73: 396-412 (1939). PLEHN, M.: Driisenzellen oder Parasiten? Anat. Anz. 29: 152-156 (1906).
C. J. DAWE, MD, Laboratory of Pathology, National Cancer Institute, National Institute of Health, Bethesda, MD. 20014 (USA)
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