Infiltration of the thyroid gland by T-cell prolymphocytic leukemia.

Background: T-cell prolymphocytic leukemia (T-PLL) is rare, accounting for only 0.06% of all malignant lymphomas, and is classified as a T-cell mature lymphoma. The disease affects mainly elderly patients and is characterized by splenomegaly, lymphadenopathy, skin infiltration, and a high leukocyte count, but thyroid filtration has never been detected as far as we could determine. We report here a case of infiltration of the thyroid gland by T-PLL.

Methods: An 89-year-old woman who had been treated for Hashimoto's thyroiditis for 20 years presented with a progressively enlarging thyroid mass accompanied by dyspnea and dysphasia. Atypical lymphocytes with irregular nuclei were observed in the peripheral blood. An open biopsy of the thyroid provided pathological evidence of T-PLL, and bone marrow examination showed infiltration by T-PLL. The diagnosis was therefore infiltration of the thyroid gland by T-PLL. Chemotherapy was initiated, but six months after termination, recurrence of neck swelling was observed. The patient was then treated with radiotherapy, but she died of a major stroke 15 months after onset.

Conclusions: This is the first report of T-PLL infiltration of the thyroid gland, reminding physicians to keep in mind a broad differential diagnosis when encountering a patient with diffuse thyroid lesions and abnormal lymphocytes in the peripheral blood.