Pheochromocytomas, PASS, and immunohistochemistry.

Differentiation between malignant and benign pheochromocytomas of the adrenal gland traditionally relies on the presence of clinically detectable metastases. The PASS system for differentiating between benign and malignant pheochromocytomas is based on defined morphological criteria, of which some are related to tumour cell proliferation and survival. Immunohistochemical markers for important events in the cell cycle were explored in order to characterise differences in apoptosis, G1 checkpoints, and S phase in more detail. A panel consisting of p53, tenascin, bcl-2, pRb, cyclin D1, mcm2, and p27 was employed. Only for pRb a statistically significant difference between PASS 3 and less and PASS 4+ tumours was detected, indicating qualitative differences in the mitotic cycle, probably immediately before early S phase. These results are discussed in relation to similar studies in recent literature.