PROGNOSTICATING TOOLS IN PRIMARY NEUROENDOCRINE (MERKEL-CELL) CARCINOMAS OF THE SKIN - HISTOPATHOLOGICAL SUBDIVISION, DNA CYTOMETRY, CELL-PROLIFERATION ANALYSES (KI-67-IMMUNOREACTIVITY) AND NCAM IMMUNOHISTOCHEMISTRY - A CLINICOPATHOLOGICAL STUDY IN 25 PATIENTS

Histopathologically, 18 of our patients had classical Merkel-cell carc inomas (MCC); seven had neuroendocrine (NE) carcinomas with features d ifferent from MCC, here called ''aberrant MCC''. These patients showed a progressive neoplastic disease with a fatal outcome in four of them . The cytometric DNA distribution pattern of the tumor cell nuclei of all the abet-rant MCCs was found to be of the aneuploid type. By contr ast, the neoplastic disease of the majority of patients with classical MCC ran a milder course; a fatal outcome occurred in only one of them . Here, the DNA ploidy pattern was of the euploid (diploid or tetraplo id) type in eight cases and of the aneuploid type in another eight. Ou r recently described ''proliferation cell index'' (PCI), based on nucl ear immunoreactivity (IR) with the proliferation ''marker'' antigen Ki -67, was significantly lower in those five MCCs of the classical ''DNA -diploid'' type than in the seven ''DNA-aneuploid'' ones. These five p atients presented a mild neoplastic disease; only one had a local recu rrence and none had metastases. Otherwise, neither the PCI values nor the NCAM IR of the MCC cells were found to be of any prognostic signif icance.