Thyroid pathology, a clue to PTEN hamartoma tumor syndrome.

Phosphatase and tensin homolog (PTEN) hamartoma tumor syndrome (PHTS) is a hereditary disorder caused by germline inactivating mutations in the PTEN tumor suppressor gene. As a type of PHTS, Cowden syndrome is associated with abnormalities of the thyroid, breast, uterus, and gastrointestinal tract. A 52-year-old-woman visited the outpatient clinic of our endocrinology clinic with multiple thyroid nodules and Hashimoto's thyroiditis. Computed tomography imaging revealed a multinodular mass measuring up to 3.5 cm in the left thyroid lobe, causing laryngotracheal airway displacement. The total thyroidectomy specimen revealed multiple follicular adenomas and adenomatous nodules with lymphocytic thyroiditis and lipomatous metaplasia in the background. The patient was suspected of PTHS based on her thyroid pathology, family history, and numerous hamartomatous lesions of the breast, uterus, and skin. Her diagnosis was confirmed through molecular testing. This case demonstrates that pathologists must be well acquainted with thyroid pathology in PHTS.