Immunohistochemical detection of proliferating cell nuclear antigen and Ki-67 in mast cell tumors from dogs.

OBJECTIVE

To determine whether immunohistochemical detection of proliferating cell nuclear antigen (PCNA) and Ki-67 correlated with prognosis for dogs with cutaneous mast cell tumors (MCT).

DESIGN

Case series.

ANIMALS

120 dogs with solitary cutaneous MCT that were excised.

PROCEDURE

Information on signalment, history, and outcome was obtained by sending a questionnaire to referring veterinarians. Tumors were graded histologically, and immunohistochemical staining for Ki-67 and PCNA was performed.

RESULTS

Survival rates 12, 18, and 24 months after surgery were significantly different among groups when dogs were grouped on the basis of histologic grade. Although mean number of PCNA-positive nuclei/1,000 tumor nuclei was significantly higher for dogs that died of MCT than for those that survived, there was great overlap in values. Mean number of Ki-67-positive nuclei/1,000 tumor nuclei was significantly higher for dogs that died of MCT than for those that survived, without any overlap in values between groups, and number of Ki-67-positive nuclei/1,000 tumor nuclei was significantly different among groups when tumors were grouped on the basis of histologic grades. For dogs with grade-II tumors, number of Ki-67-positive nuclei/1,000 tumor nuclei (< 93 vs > or = 93) was significantly associated with outcome (survived vs died).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that for dogs with solitary cutaneous MCT, determining number of Ki-67-positive nuclei may be useful in predicting prognosis, particularly for dogs with grade-II tumors.