Immunocytochemical localization of calcitonin-producing cells in a strumal carcinoid with amyloid stroma

A nonfunctioning strumal carcinoid arising in a 49-year-old woman was studied by histochemical and immunocytochemical techniques. All tumor cells, irrespective of their architectural arrangement, showed properties of neuroendocrine-programmed cells, without any evidence of thyroid follicular cell differentiation. Foci of calcitonin-producing C-cells were demonstrable by immunocytochemical technique and were closely associated with areas of amyloid stroma of the tumor. Efforts at localization of insulin and gastrin within the tumor cells gave negative results. While the results in the present case offer additional support for an APUD cell origin of strumal carcinoids, the presence of the calcitonin-producing C-cells within the tumor raises interesting histogenetic possibilities as to whether these lesions are derived from C-cells or represent an ovarian carcinoid with foci of C-cell differentiation.