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[Review of the misdiagnosed cases focusing on the quality control of histopathological diagnosis].

A serious problem for every pathologist is how to avoid making errors in histopathological diagnosis. Five cases which I misdiagnosed or nearly did were reviewed, and the ways to avoid making errors were discussed. The first case was clinically a gastric carcinoma. In the biopsy of gastric mucosa, I took a lymphoepithelial lesion for poorly differentiated adenocarcinoma. In the surgical specimen, the histological diagnosis was malignant lymphoma. The second case was a tumor of cecum. Clinically cecal cancer was suspected and operated due to the complication of invagination. Histological examination of cecal tumor revealed marked lymphocytic infiltration with plasma cells. The immunohistochemistry showed a mixed pattern of B- and T-lymphocytes with monoclonal proliferation of plasma cells (IgA, Kappa). Because an inflammatory polyp could not be ruled out, it was offered to consultation. The diagnosis was malignant lymphoma, lymphoplasmacytoid type. The third case was a neck tumor. Although histological diagnosis at first was undifferentiated carcinoma, immunohistochemically tumor cells were unexpectedly negative for epithelial membrane antigen and positive for creatine kinase-mm. Finally it was diagnosed as rhabdomyosarcoma. The fourth case was a struma nodosa. In the frozen section, it was diagnosed as follicular adenoma. However, in the permanent section, the diagnosis was corrected to papillary carcinoma, follicular type, because many intranuclear inclusions were clearly observed. The last case was a finger tumor. Since hemangiosarcoma could not be histologically ruled out, it was offered to consultation. The diagnosis was intravascular papillary endothelial hyperplasia. In conclusion, I emphasize the importance of consultation in order to avoid making errors in histopathological diagnosis.