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Two sisters at risk for hereditary medullary carcinoma and having small but progressive increases of serum calcitonin in response to calcium infusion underwent thyroidectomy. The thyroid glands were studied for C-cell distribution. Middle and upper portions of the lateral thyroid lobes showed marked increases and clustering of calcitonin-containing cells in comparison with normal thyroid glands. Elevated calcitonin content (670 to 4100 Medical Research Council mU per gram), as compared to similar regions in normal thyroid tissue (<0.6 to 50.0 Medical Research Council mU per gram), correlated precisely with the cytologic localization. Histologic characteristics of the cells had the appearance of a preinvasive hyperplastic process. A third case from another kindred was studied with similar findings. C-cells thus appear to be distributed inhomogeneously in normal human thyroid tissue; an early change in persons destined to development of hereditary tumors of these cells is a multicentric, but anatomically restricted, increase in numbers of cells. (N Engl J Med 289:437–441, 1973)
Wolfe et al. (Thu,) studied this question.