Feline melanoma: a comparative study of ocular, oral, and dermal neoplasms

Melanomas diagnosed in 29 cats over an 11 year period included 19 ocular (16 intraocular, three palpebral), five oral, and five dermal melanomas. Intraocular melanomas involved the ciliary body and iris in 12; the whole eye was involved in four. The average age of cats with intraocular melanomas was 11 years; the female : male ratio was 9 : 7. Histologically, eight intraocular tumors were mixed, six were epithelioid, and two were spindle cell. Ten of 16 cats (62.5%) with intraocular melanomas were killed because of the tumor at a mean of 156 days; four are living with no evidence of disease (average, 255 days). The mean time of death in cats with palpebral melanoma was 409 days. Metastasis occurred in 63% of cats with intraocular melanoma and all cats with palpebral melanoma. Four cats with oral melanoma were killed at a mean of 61 days; all had metastasis. Of five cats with cutaneous melanoma, one was killed with metastasis at 90 days; three cats were alive without evidence of recurrence or metastasis greater than 365 days after surgery. Results of this study indicate that in the cat, ocular melanomas are more common than oral and dermal melanomas, and ocular and oral melanomas are more malignant than dermal melanomas, with higher rates of mortality and metastasis.