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Background. The diagnosis of medullary thyroid carcinoma (MTC) depends on the calcitonin immunohistochemistry. Familial MTC is associated with C-cell hyperplasia (CCH), whereas sporadic MTC is not. A specific and sensitive calcitonin immunohistochemistry is necessary for the diagnosis of MTC and CCH. Methods. An affinity-purified anti-calcitonin antiserum APxCT) was used for immunohistochemistry of the thyroids of 15 patients with MTC. The thyroids of five patients with familial MTC were studied in detail, with each gland sectioned in 48 areas. Results. Between three and ten independent MTC were found in each thyroid, and CCH was found in all five patients (24.2%, varying from 8.4-56.3% of the 48 areas from each thyroid). MTC and CCH were localized mainly in the middle third and in the central axis of the thyroid lobes. They often were found together in the same area (in a total of 21 areas for the five thyroids sectioned in 48 areas) but ten areas with MTC did not have CCH, and 37 areas with CCH did not have MTC. In ten thyroids partially studied, CCH was indicated in three patients thought to have sporadic MTC. In two thyroids, with follicular and papillary carcinoma, a higher density of C-cells was found around the tumors, but disease was not characterized as CCH. Conclusions. APxCT antiserum increased the immunohistochemical specificity and sensitivity. The distinction of the familial from the sporadic MTC requires a careful and extensive search of CCH. C-cells in high density may be found around follicular cell carcinomas, being a potential source of diagnostic error.

Prostatic needle biopsies from 142 patients were studied: 61 cases were “benign”, 19 atypical small acinar proliferation, 31 high-grade prostatic intraepithelial neoplasia, and 31 adenocarcinoma. Using univariate analysis of 46 previously described morphological features, 16 variables were selected, which were followed by multivariate discriminant analysis. Of these parameters, seven (glandular fusion, crystalloids, nucleolomegaly, papillary architecture, visibility of basal cell layer, areas of normal luminal cell nucleus/cytoplasm ratio and areas of high luminal cell nucleus/cytoplasm ratio) remained significant in discriminating the groups. Multivariate analysis selected a small panel of histological features as those most helpful in the differential diagnosis of proliferative lesions in prostate biopsies.