Wk. Vogelbein et Jw. Fournie, ULTRASTRUCTURE OF NORMAL AND NEOPLASTIC EXOCRINE PANCREAS IN THE MUMMICHOG, FUNDULUS-HETEROCLITUS, Toxicologic pathology, 22(3), 1994, pp. 248-260
The ultrastructure of exocrine pancreatic neoplasms occurring in the m
ummichog, Fundulus heteroclitus, from a creosote-contaminated site in
the Elizabeth River, Virginia, is described and related to nonneoplast
ic exocrine pancreas. Normal mummichog pancreas was an anastomosing tu
bular gland, with parenchymal cells organized as branched, anastomosin
g tubules around a central ductular system. The pancreatic ductular sy
stem consisted sequentially of terminal canalicular lumens lined by ac
inar cells, pancreatic preductules formed by an acinar and a centroduc
tular cell, pancreatic ductules lined by 2 centroductular cells, and p
ancreatic ducts lined by cuboidal or columnar epithelial cells resting
on a basal lamina and stromal sheath. Acinar cell adenomas retained t
he normal tubular organization and relationship between acinar and cen
troductular cells. Tumor cells exhibited nuclear pleomorphism but cont
ained a full complement of normal zymogen granules and rough endoplasm
ic reticulum (RER). Some adenomas exhibited necrosis and cellular dege
neration. Acinar cell carcinomas ranged from well to poorly differenti
ated. They exhibited loss of cell polarity, moderate to severe nuclear
pleomorphism, extensive variation in size, shape, and number of zymog
en granules, variability in RER content, and cellular degeneration. Ac
inar cell neoplasms in the mummichog were similar to those induced che
mically in other fishes and certain mammals, suggesting that this fish
population has been exposed to potent chemical carcinogens and that t
he species may be an effective indicator of polluted estuarine environ
ments.