Primary thyroid
lymphoma is a
rare disease that continues to produce diagnostic and therapeutic dilemmas. There was great difficulty in distinguishing thyroid
lymphoma from
anaplastic thyroid carcinoma but, because of new immunocytochemical staining techniques and increased cytopathologic knowledge, our ability to diagnose thyroid
lymphoma has improved drastically over the past decade. Surgery that was once the mainstay of treatment for this disease, now plays a minimal role. Current treatment regimens for primary thyroid
lymphoma consist of
chemotherapy (
cyclophosphamide,
doxorubicin,
vincristine, and
prednisone) and external beam radiation. The overall and distant relapse rates have been shown to be significantly lower in those patients receiving
combined modality therapy compared to
chemotherapy or radiation alone. Although the role of surgery has changed over time, it continues to play an important role, especially in confirming diagnoses through open biopsies, potentially providing local control in the more indolent subtypes, and may play a role in the palliation of symptoms for large obstructive
lymphomas. The evolving classification of extranodal
lymphomas has brought about a better understanding of the
biologic behavior of these
tumors. Most thyroid
lymphomas are B-cell origin, with six different histologic subtypes, but there appears to be two distinct clinical and prognostic groupings of these rare
tumors. The more indolent
lymphomas are the subgroup of mucosa-associated lymphoid tissue (
MALT) lymphomas comprising approximately 6% to 27% of thyroid
lymphomas. This subgroup, when localized to the thyroid (stage IE), responds well to total
thyroidectomy or radiation with a complete response rate of more than 90%, leading some authors to recommend surgery as primary
therapy in the treatment of localized
MALT lymphomas. Therefore, surgery as a primary treatment for thyroid
lymphomas would only be recommended under ideal conditions, such as MALT subtype stage IE only, and completely resectable with minimal morbidity. Unfortunately, this scenario is rarely the case. The more common subtype, comprising up to 70% of cases, is
diffuse large B-cell lymphoma. This subtype appears to have the most aggressive
clinical course with almost 60% of these
tumors diagnosed with disseminated disease. Up to 40% of all
diffuse large cell lymphomas appear to have undergone transformation from a
MALT lymphoma, but they behave in a similar fashion to
diffuse large cell lymphomas. Treatment for these
tumors should include
chemotherapy and radiation. The overall 5-year survival for this aggressive group is less then 50%. Surgery is rarely beneficial in
diffuse large cell lymphoma and the mixed large cell subtypes because the disease is generally disseminated and surgical excision of all disease is not possible or associated with increased morbidity. However, there may be a role for palliative surgical debulking to alleviate obstructive symptoms while the patient is undergoing standard
chemotherapy and radiation.