Pheochromocytomas, uncommon adrenal tumors, have an uncertain behavior. Recently, PASS criteria were proposed for differentiating between benign and malignant cases. These are not perfect, however. The aim of the study was to investigate angiogenesis and mast cell density in context of the clinical behavior and morphologic characteristics of pheochromocytomas.

Mean intratumoral chymase positive cell count was 14.50 for malignant, 15.73 for benign cases; mean subcapsular chymase positive cell count was 12.50 for malignant, 11.27 for benign cases. Mean intratumoral tryptase positive cell count was 17.50 for malignant and 17.91 for benign cases; mean subcapsular tryptase positive cell count was 15.25 for malignant and 15.73 for benign cases. Mean intratumoral CD31 positive vessel count was 46.98 for malignant and 51.02 for benign cases; mean subcapsular CD31 positive vessel count was 44.86 for malignant and 39.81 for benign cases. Mean intratumoral CD105 positive vessel count was 37.84 for malignant and 35.95 for benign cases; mean subcapsular CD105 positive vessel count was 26.36 for malignant and 22.03 for benign cases. The differences between benign and malignant cases were not significant. All the vascular counts were correlated with mast cells counts. PASS index was inversely correlated with mast cell counts.