Electron microscopy in an oncologic institution. Diagnostic usefulness in surgical pathology.

A retrospective survey of all electron microscopic (EM) examinations of surgical pathology specimens obtained at the Istituto Nazionale Tumori of Milan over a 5-year period (1981-1985) was carried out. During this time a total of 259 cases were examined: for 97 (38%) electron microscopy provided a substantial diagnostic contribution, whereas in 151 (58%) it confirmed the previous light microscopic diagnosis. In our experience, EM was most useful for diagnosing selected cases of cutaneous malignant melanoma predominantly metastatic, rhabdomyosarcoma, neuroblastoma and poorly differentiated neuroepithelial tumors and less helpful in the further analysis of cases of malignant mesothelioma, Ewing's sarcoma, leiomyosarcoma and fibrohistiocytic malignancies. In cases of well-differentiated neuroepithelial tumors, such as carcinoids, EM data was essentially confirmatory of (immuno)-histochemical findings.