Pigmented Dermal Neoplasms in Gizzard Shad

Dermal neoplasms composed of fusiform cells and containing melanin were found in adult gizzard shad (Dorosoma cepedianum) in an unpolluted reservoir in Oklahoma (Ostrander et al., 1995; Jacobs and Ostrander, 1995). The cell of origin of these tumours is unknown but could be melanocytes, nerve sheath cells, or fibroblasts. Mean prevalence in adults (2-5 years old) was 22.1% in several samples collected over nearly 3 years, but grossly visible neoplasms were not found in juveniles. Prevalence of these neoplasms did not appear to be seasonal. There was no evidence from electron microscopy and reverse transcriptase assays that a virus was involved.

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