Plasma cell neoplasm involving the thyroid.

Involvement of the thyroid gland by plasma cell neoplasms is very rare. On review of 248 cases, we found 4 cases in which pathological evidence of plasma cell neoplasm in the thyroid was verified. This was a heterogeneous group of patients; the thyroid involvement was clinically recognized as a site of extramedullary plasma cell neoplasm in one patient and as a part of generalized disease in two patients. In another patient with generalized disease, the thyroid involvement was discovered at autopsy.