A fibrosarcoma in a Siamese crocodile (Crocodylus siamensis).

A fibrosarcoma of periosteal origin was identified in the oral cavity of a 22-yr-old male captive Siamese crocodile (Crocodylus siamensis). The diagnosis was based upon the gross and light microscopical examination. The mesenchymal histogenesis was derived from the capability of the cells to produce collagen fibers. The invasive growth and the polymorphous cells in combination with the low mitotic index suggest a low-order malignancy. Attempts by immunohistochemical staining techniques to identify the specific lineage of the neoplastic cells and the expressed collagen type were unsuccessful.