Df. Kusewitt et al., S-100 IMMUNOREACTIVITY IN MELANOMAS OF THE SOUTH-AMERICAN OPOSSUM MONODELPHIS-DOMESTICA, Veterinary pathology, 34(4), 1997, pp. 346-350
S-100 immunoreactivity was determined 1) in foci of melanocytic hyperp
lasia, 2) in naturally occurring, ultraviolet radiation-induced, and 9
,10-dimethyl-1,2-benzanthracene (DMBA)-induced primary melanomas, and
3) in metastatic melanoma lesions in the South American opossum Monode
lphis domestica. Preneoplastic lesions of melanocytic hyperplasia cont
ained scattered cells with S-100-positive nuclei. All primary melanoma
s, with the exception of a single DMBA-induced tumor, contained cells
with S-100-positive nuclei. The pattern of S-100 reactivity in tumors
varied from large foci of S-100-positive cells to scattered individual
S-100-positive cells. Lymph node metastases were S-100 positive, but
metastatic masses in internal organs were usually S-100 negative. Alth
ough S-100 reactivity did not distinguish preneoplastic lesions from t
umors or benign melanomas from malignant melanomas, identification of
metastatic tumor cells clearly demonstrated malignancy.