Thyroid lymphoma is a relatively rare disease, constituting fewer than 1% of all lymphomas and accounting for 2% of extranodal non-Hodgkin’s lymphoma.58 Almost all of these thyroid lymphomas are non-Hodgkin’s lymphoma, with the majority (70% to 90%) being intermediate grade and the remainder being high grade (see Chapter 127). Many are considered mucosa-associated lymphoid tissue lymphomas (MALTomas), show plasmacytic differentiation, and may be associated with similar lesions in extranodal sites, especially in the gastrointestinal tract.

The majority of patients with thyroid lymphoma have disease on one side of the diaphragm with a proportion confined to the thyroid (stage IE). The majority have thyroid disease plus cervical or mediastinal lymph nodes (stage IIE).58 The incidence of this disease may be changing, primarily due to improved recognition and diagnosis of thyroid lymphoma. One hypothesis to explain the incidence increase is that these patients were previously diagnosed as having anaplastic thyroid carcinoma and, with better understanding and more sophisticated diagnostic tools, such as immunohistochemistry, these patients are now being correctly categorized as having thyroid lymphoma.

In most series, there is a strong female predominance, ranging from 3:1 up to 8:1. The median age in most series at diagnosis places patients in the seventh decade of life, similar to what is seen for ATC and much older than patients with well-differentiated thyroid cancer. Between 10% and 30% of patients report a symptom or combination of symptoms relating to local invasion, including hoarseness ...