Figure 8 illustrates a cholangiocarcinoma. When these lesions are large, as is 
evident in many histologic sections, they are grossly apparent. There are many 
morphologic variants of the tumors I have shown. 
Some neoplasms are well-differentiated and relatively uniform in architecture. 
However, there are morphologic variants of cholangiocarcinomas that are very bizarre. 
The morphologic patterns of the neoplasms resemble those induced in rodents with 
experimental carcinogens. 
Figure 9 shows a carcinoma that a pathologist would characterize as 
anaplastic. An anaplastic neoplasm is one whose constituent cells are not well 
differentiated and which do not resemble those of normal tissue. Numerous mitotic 
figures are present, some very large and containing excess numbers of chromosomes 
(polyploid). All of these features are characteristic of lesions which generally are 
metastatic; however, whether these lesions metastasize presently is unknown. 
Figure 10 illustrates chromatically distinct cells in cardiac muscle that are not 
inflammatory cells, that is they are not leukocytes. If one looks at the lesion at higher 
magnification, the cells resemble hepatic tumor cells, cells of a hepatic carcinoma. This 
could be the first metastasis documented in these fish. This finding suggests that these 
fish have a lesion which is biologically or behaviorally comparable to that of warm¬ 
blooded animals and, therefore, might take the same course. 
I will finish by showing you the gross lesions last because they will impress you 
more than the photomicrographs. If you have ever seen a normal winter flounder liver, 
you know that it is essentially homogeneous in color, usually coffee-brown, although the 
color depends on the nutritional status of the fish and the time of the year. The liver in 
Figure 11 is not normal. Almost all of the discrete, nodular areas are tumors. The 
specific kind of tumor is unknown until one examines the tissues microscopically. I also 
have shown you the worst-case situation to impress you. I did not show you pictures of 
livers with only a few nodules; however, they are quite common. 
Boston Harbor winter flounder with tumors look normal like their cohorts. 
One could easily ask whether the lesion has any significance on the health of the fish. 
There is much to do to resolve what the lesions ultimate effect is, either for individual 
fish or populations of fishes. 
In closing I would like to acknowledge the assistance provided me by Dr. Clyde 
Dawe formerly of the National Cancer Institute, and now at Harvard Medical School and 
Woods Hole. Dr. Dawe first described hepatic neoplasms in wild fish from polluted water 
and his assistance and interest have been invaluable. He has made all of the collecting 
trips with me, in fact, he made one trip without me because of lack of funds for my travel 
to Boston from Maryland. Thank you. 
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