Cytotoxic T-cell non-Hodgkin's lymphoma of the thyroid gland.

An 86-year-old female was diagnosed with peripheral T-cell lymphoma, unspecified, which affected only her thyroid gland. Lymphoma cells were TIA-1(+), suggesting cytotoxic T-cell origin. She had not suffered from autoimmune thyroiditis and showed normal thyroid function. Without any specific therapies, the lymphomatous lesion showed the partial spontaneous regression before diagnostic hemithyroidectomy, and she had been well for 2 years without relapse. This is the first case of primary thyroid lymphoma of cytotoxic T-cell origin that showed spontaneous regression.