- 2 - 
consistent for amebae (Dawe, C. J., J. Bagshaw, and C. M. Poore. Amebic 
Pseudotumors in Pseudobranchs of Pacific cod, Gadus macrocephalus. Proc. 
70th Annu. Meet. Am. Assoc. Cancer Res., 245, 1979J. thus, *'x-ceir' 
tumors are parasitic lesions, not neoplasms as previously reported. This 
explains certain long recognized non-neoplastic features of these lesions 
such as negative Feulgen reaction by "x-cells" and occasional granuloma¬ 
tous reaction to them. It also provides an explanation for the incon¬ 
sistent results of attempts to correlate their occurrence with pollution. 
Future workers will need to differentiate the amebic "x-cell" adenoma¬ 
like and papilloma-like lesions from true epithelial neoplasms of 
Osteichthyes such as papilloma in red drum (RTLA 1904 from Allyn Johnson), 
white sucker (RTLA 1907 from John Hnath), and koi carp (RTLA 1901 from 
Harold Wolf). So far amebic "x-cells" are unknown from papillary le¬ 
sions in any non-bony fish species such as fibropapilloma in green sea 
turtles (RTLA 1856, 1883 from George Balazs) and epidermal papilloma in 
a green lizard (RTLA 1917 from Edward Elkan). This lizard papilloma did 
contain virus-like nuclear inclusions, however. 
Among the interesting and significant accessions were five cases 
of hepatocellular carcinoma in Atlantic tomcod from the Hudson River con¬ 
tributed by Charlie Smith (RTLA 1868-1872). The Hudson is heavily pol¬ 
luted by polynuclear aromatic hydrocarbons (PAH's). PAH's in fish are 
chiefly modified for excretion by liver enzymes with the presumed pro¬ 
duction of activated intermediates which are carcinogenic. Fish liver 
cancer has been experimentally induced by exposure to a number of PAH's 
known to be carcinogenic in rodents. These observations support the 
hypothesis that these tomcod carcinomas are indicative of carcinogenic 
PAH's in their environment. 
The first and only known liver neoplasm in cartilaginous fish was 
a well-differentiated hepatocellular adenoma in a stingray (RTLA 1851). 
This specimen, and two other Chondrichthyes contributed by Prince 
Masahito (RTLA 1852, 1853), also had thyroid hyperplasia. Additionally, 
thyroid hyperplasia was seen in an Osteichthyes --a flagfish from 
Virginia Snarski (RTLA 1952). 
A valuable group of 40 accessions (RTLA 2001-2040) was received 
from the Japanese Registry of Tumors in Poikilothermic Animals courtesy 
of Dr. Ikuo Kimura and Dr. Masao Ito. Among these were ameloblastoma 
in salmon, hepatocellular neoplasms in various salmonids, ovarian neo¬ 
plasms in carp, melanophoroma in croaker and rainbow trout, nephroblas¬ 
toma in rainbow trout and Japanese eel, adenomatous stomach polyps in 
salmon, fibroma in walleye pollack, retinoblastoma in green swordtail 
and meningioma in Permatochromis kribensis . 
In addition to the two central nervous system (CNS) neoplasms from 
the Japanese tumor registry, an invasive esthesioneuroepithelioma near 
the lateral line of a goldfish (RTLA 1931 from Harold Wolf) may be the 
first CNS tumor arising from the vagus nerve. Neuroblastoma in platy- 
fish/swordtail hybrids (RTLA 1930 from M. Schwab) were induced by N- 
Methyl-N-Nitrosourea. 
