Cytological findings in medullary carcinoma of the thyroid

In six cases of medullary carcinoma of the thyroid rather characteristic findings were seen in cytological specimens obtained by aspiration or imprint. The roundish-polygonal or spindle-shaped cells were predominantly disseminated, but occasionally arranged in small groups. The nuclei were frequently found in an excentric position; binuclear cells were sometimes encountered. In addition, five of the six cases showed intranuclear cytoplasmic inclusions which were also investigated by electron microscopy in specimens of two cases. Such inclusions in aspiration biopsies of the thyroid have so far been regarded, as characteristic for papillary carcinoma. In smears as well as in histological sections amyloid and calcitonin could be demonstrated by congo red staining and by immunocytochemistry, respectively. The cytomorphology of the tumor cells, their pattern of arrangement, and the peculiar nuclear inclusions make up a combination of findings that may justify the diagnosis of medullary carcinoma in aspiration biopsies. In smears the diagnosis can already be confirmed when (immuno-) cytochemical methods are applied to smear preparations.