MAST CELL TUMORS IN CHEETAH (ACINONYX JUBATUS): A CASE SERIES.

Mast cell tumors in nondomestic felids are rarely reported and their biological characteristics are not well described. A retrospective review of the pathology records of 52 zoo-housed cheetahs (Acinonyx jubatus) identified five cases of mast cell tumor, involving four closely related individuals. The age at initial presentation varied from 14 mo to 6 yr. Four cases presented as solitary or multiple cutaneous masses that were mostly slow growing, up to 20 mm diameter, and predominantly nonulcerated. The diagnosis was made by fine needle aspiration cytology of a lesion in one case and by excisional biopsy in the others. Histopathologically, the lesions resembled low- to intermediate-grade canine mast cell tumors, with variations in the degree of anisocytosis and anisokaryosis. Surgical excision was incomplete for 80% of the cutaneous lesions, but local recurrence was not observed in any case. One animal with cutaneous lesions subsequently developed fatal visceral mastocytosis involving the spleen, liver, and adrenal gland. There was no evidence of lymph node invasion or paraneoplastic gastrointestinal signs in any of the cases.

KIT mutations in mast cell tumours from cheetahs (Acinonyx jubatus) and domestic cats (Felis catus).

Mast cell tumours (MCT) have been documented in numerous species and mutations within the KIT proto-oncogene are implicated in the neoplastic biology of mast cells in humans, dogs and cats. This study determined high KIT gene nucleotide and Kit amino acid sequence homology between several species known to suffer mast cell neoplasia and especially high sequence conservation between the cheetah (Acinonyx jubatus) and domestic cat (Felis catus) KIT sequences. As a result, we hypothesised that KIT mutations would exist in the neoplastic DNA of four cheetahs diagnosed with MCT from a recent case series. PCR and Sanger sequencing identified conservative exon 6 KIT mutations in two of the four cheetahs. The mutations were different between the two cheetahs. Only wild-type DNA in exons 6, 8, 9 and 11 of KIT was observed in the MCTs of the remaining two cheetahs. Twenty cutaneous MCTs from domestic cats were collected for KIT mutation comparison. Twelve tumours possessed a mutation within KIT exons 6, 8 or 9 (60%, 95% CI 38.5%-81.5%). No mutations were detected in exon 11. There was no significant association between domestic feline MCT KIT mutation status and tumour histological grade (traditional schematic, P = .934; Sabattini 2-tier schematic, P = .762) or mitotic index (P = .750). KIT mRNA and Kit protein sequences are conserved across species but the role of KIT in feline MCT pathogenesis is not completely understood.