A critical reassessment of the concept of C-cell hyperplasia of the thyroid - A quantitative immunohistochemical study

We performed a retrospective quantitative immunohistochemical analysis of C-cells in 150 thyroids obtained at autopsy from 86 men and 64 women >50 years of age (range, 53-92 years) without clinical evidence of thyroid disease. Evaluation of the immunostaining results was performed at low power (100x). C-cells were counted in 50 consecutive low-power fields (LPFs) per slide, which corresponds to a total area of 1.26 cm(2)/slide and 35.28 cm(2)/gland. C-cell density per gland was expressed as the number of C-cells per cm(2). An LPF containing at least 50 C-cells was set as the threshold for hyperplasia. In 104 glands (69.3%) there were LPFs with at least 50 C-cells. The age range of these subjects was 56 to 92 years (mean, 67.84 +/- 12.48 years); 67 (64.4 %) were men and 37 (35.6%) were women. The number of C-cells per thyroid varied from 116 to 3,314; C-cell density per thyroid varied from 3.28 to 93.93 cells/cm(2). Fields with at least 50 C-cells per slide varied from one to 48 per thyroid; in 20 (19.2%) glands, they also occurred in both lobes. Fields with at least 50 C-cells were observed in 48 (65.7%) thyroid glands without histopathologic changes, in 23 (71.8%) with nontoxic nodular enlargement, in 15 (75%) with chronic inflammation, in eight (66.6%) with latent papillary carcinomas, and in 10 (76.9%) with metastases from extrathyroid tumors. Fields with at least 50 C-cells were found in 34 (77.3%) thyroid glands from patients with malignant extrathyroid tumors, in six (75%) with chronic renal failure, in 22 (81.4%) with gastric duodenal ulcer, in eight (44.4%) with hepatic cirrhosis, in two (1008) with diabetes mellitus, and in 32 (54.2%) with cardiovascular and respiratory diseases. The statistical analysis showed that there was no significant statistical difference in both C-cell number and C-cell density between men and women and between subjects with and without malignant tumors. The results of the present study show that in the thyroid of adults >50 years of age, fields with at least 50 C-cells, a number usually employed as the threshold for C-cell hyperplasia, are a common finding. We believe that the presence of LPFs with at least 50 C-cells could represent a physiologic C-cell component of thyroids in subjects >50 years of age.