Immunohistochemical and clinical evaluation of p53 in canine cutaneous mast cell tumors

One hundred twenty-six cutaneous mast cell tumors obtained by excisional bi opsy from 106 dogs were evaluated using immunohistochemical staining for th e presence of p53 protein. a standard avidin-biotin immunohistochemical pro tocol was used incorporating a polyclonal antibody of rabbit origin (CM-1) as the primary antibody. Histopathologic grading of tumors was performed on hemotoxylin and eosin-stained samples. There was a significant difference in the percentage of cells staining positive for p53 for the histopathologi c grades (P = 0.0005). Grade III tumors had a significantly greater p53 con tent than did grade I or II turners (P < 0.05). Clinical data obtained retr ospectively was available for 54 dogs. Tumor recurred in 19 of 54 (35.2%) d ogs. Twenty-nine dogs died by the end of the study; 9 of 29 (31.0%) died of mast cell tumor disease. Histopathologic grade showed a significant negati ve association with survival time. Both clinical stage and histopathologic grade showed a significant negative association with time to recurrence. Th e percentage of cells staining positive for p53 did not significantly impro ve the forward analysis. Immunohistochemical detection of p53 did not appea r useful in characterizing the clinical association between cutaneous mast cell tumor cellular features and survival time or time to tumor recurrence in dogs.