A Plurihormonal TSH-Producing Pituitary Tumor of Monoclonal Origin in a Patient with Hypothyroidism

OBJECTIVE: A clinicopathological and clonal study of a pituitary tumor was made in a 26-year-old woman with chronic thyroiditis to differentiate TSH-producing adenoma from TSH hyperplasia. METHODS: Tumor specimens were subjected to histopathological study and clonal analysis (HUMARA). RESULTS: Immunohistochemical examination disclosed TSH-beta, PRL, GH, ACTH, FSH-beta, LH-beta, and alpha-subunit production in the adenoma cells. These heterogeneous phenotypes are characteristic of both thyrotroph hyperplasia and plurihormonal TSH-producing adenoma. However, the HUMARA method demonstrated monoclonality of the tumor cells. CONCLUSION: Monoclonality of the tumor cells proved that the pituitary tumor was plurihormonal TSH-producing adenoma, not TSH hyperplasia.