Immunohistochemical and flow cytometric study of neuroendocrine carcinoma of the skin

Immunohistochemical and flow cytometric analysis using formalin-fixed, paraffin-embedded sections was performed on 10 neuroendocrine carcinomas of the skin (NCS). Grim-elius staining was positive in seven tumors. All tumors showed coexpression of CAM 5.2 and neuron-specific enolase with paranuclear dot-like or diffuse cytoplasmic reactivity. Neuro-filament was positive in five cases, chromogranin in six, calcitonin and carcinoembryonic antigen in two each, and somatostatin and S-100 protein in one each. Eight primary lesions were diploid and the remaining two were aneuploid; however, two diploid NCS presented as aneuploid metastatic tumors. The follow-up periods ranged from 3 to 66 months (mean 13.6). Six patients died of metastatic diseases between 3 and 33 months (mean 9.2) after the diagnosis. There were no significant correlations among histologic features, DNA ploidy, S-phase fraction, and clinical outcome of the patients with NCS. These results indicate that a panel of antibodies may be required for immunohistochemical confirmation of neuroendocrine differentiation and that a flow cytometric analysis is not a good tool to predict the biologic behavior of NCS.