Background
Primary thyroid lymphoma can be defined as a lymphoma that arises from the thyroid gland. This definition excludes those that invade the thyroid gland as a consequence of either metastasis or direct extension. Primary thyroid lymphomas are practically always of the non-Hodgkin type. Primary thyroid Hodgkin disease is extremely rare. Non-Hodgkin lymphomas (NHLs) can be further divided into aggressive and indolent cell types. The aggressive NHLs comprise a large number of cell types, the most common of which is large cell lymphoma. They most frequently arise from lymph nodes, but an extranodal site can be the primary source in approximately 30% of cases and the thyroid gland is among the most common of these extranodal sites.
Thyroid lymphomas constitute only 3% of all NHLs and approximately 5% of all thyroid neoplasms.[1, 2, 3] Thyroid NHL, although not a very common disorder, is highly curable, without the need for extensive surgery and, for this reason, should be recognized early and treated correctly.
Note the image below.
Rapidly enlarging thyroid mass occurring in association with neck adenopathy. Pathophysiology
Interestingly, these disorders are very frequently associated with Hashimoto thyroiditis (HT). Conversely, there is a markedly increased incidence of primary thyroid lymphomas in patients with HT and it is thought that there is very likely a pathogenetic link between this autoimmune disorder and thyroid NHL.[4] Hypothyroidism has been observed in 30-40% of patients with thyroid lymphoma. As expected because of its association with HT, thyroid lymphomas occur more commonly in females, with a female-to-male ratio ranging from 2:1 and as high as 14:1 in some series.[2, 5] Similar to other NHLs, the median age is usually close to 60 years.[6]
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