[Ultrastructural analysis in differential diagnosis of tumors].

Ultrastructures of 25 tumors were analyzed by electron microscopy (EM). Of the 25 cases, there were 9 amine precursor uptake and decarboxylation tumors (APUD) (2 carotid body tumor, 2 medullary carcinoma of thyroid and 5 carcinoid) in which the dense core granules of different sizes were seen in the cytoplasm. 4 cases of malignant melanoma were identified by EM basing on the premelanosome and melanosome in the cells. In 4 carcinomas from different locations, 2 had mucous secretory granules in the cytoplasm and junction complex between the tumor cells. The diagnosis was finally confirmed as adenocarcinoma. The other 2 cases were identified as epidermoid carcinoma or anaplastic carcinoma as desmosome and tonofilaments were found. 4 cases of malignant lymphoma without any cell junction complex were identified. Moreover, there were several cases of mesenchymal cell tumors, such as leiomyoma, rhabdomyosarcoma, chordoma and Schwannoma confirmed by their special organelles. This study shows that the ultrastructural analysis is valuable in the differential diagnosis and classification of tumors.