Abnormal distribution and hyperplasia of thyroid C-cells in PTEN-associated tumor syndromes

Cowden's disease (CD) and Bannayan-Ruvalcaba-Riley syndrome (BRRS) are allelic disorders characterized by multiple hamartomatous overgrowths of the thyroid, breast, skin, and gastrointestinal tract, and an increased risk of developing benign and malignant tumors of the breast and thyroid gland, secondary to germline point mutations in the PTEN gene. In contrast to thyroid epithelial lesions, abnormalities of the C-cells are currently not considered part of the spectrum of manifestations seen in PTEN-associated syndromes.

The thyroid glands from two patients with overlapping CD/BRRS phenotypes, and with distinct PTEN mutations, were entirely submitted for histopathological examination, calcitonin immunostaining and C-cell mapping.

Multiple follicular adenomas and adenomatous nodules were present in the thyroid glands from both patients. A microscopic focus of papillary carcinoma was also present in one gland. C-cell hyperplasia was documented in both cases by calcitonin immunostaining.

PTEN-associated tumor syndromes should be considered in the differential diagnosis of C-cell hyperplasia of the thyroid.