Ultrasonographic Characterization of Cervical Lymphadenopathy in Chronic Autoimmune Thyroiditis

C hronic autoimmune thyroid disease (CAT) is a globally prevalent condition. Cervical lymphadenopathy found in conjunction with nodular thyroid disease is a potentially problematic finding that raises the specter of a malignant process. Previously held notions that autoimmune thyroid diseases with thyroid nodules were less likely to be malignant have been questioned (1,2). Pseudonodule formation can be a prominent feature of Hashimoto's thyroiditis, a form of CAT, but these can often be distinguished from true nodular disease on orthagonal imaging by ultrasound (3). Therefore, nodular and nodal findings in autoimmune thyroid patients need to be evaluated with the same clinical rigor as any other nodular disease and as directed by current clinical guidelines.

In order to better characterize the cervical lymph node findings on ultrasound in autoimmune thyroid disease, Brancato et al. (4) have undertaken a prospective description of the size, number, anatomic location, and ultrasonographic characteristics of cervical lymph nodes in 106 CAT patients compared to 70 healthy control subjects without biochemical or ultrasonographic evidence for CAT. They report that CAT is associated with a significantly higher number of total lymph nodes with a long axis greater than 1 cm in cervical levels II, III, and IV compared to the healthy control group. In addition, the short axis diameter of lymph nodes in levels III and IV was greater in the CAT patients than in the healthy control group. Furthermore, the CAT group was also more likely to have lymph nodes with a hilus demonstrated on ultrasonography (suggestive of reactive process) than the control group. The authors conclude that an increased number of benign hyperplastic-appearing lymph nodes, especially in levels II, III, and IV, is characteristic of CAT. This report represents the first systematic characterization of cervical lymphadenopathy in the CAT population (5).

Lymphadenopathy coincident with an autoimmune inflammatory disease is a common finding and has been reported in cases of nonthyroidal autoimmune processes (6). Lymphadenoapthy may be a reflection of the inflammatory state or an active participant in the inflammatory process. Given our vigilance toward lymphadenopathy as it relates to malignancy, it is important to appreciate its prevalence and benignity in CAT. These observations may assist in confirming the diagnosis of CAT in addition to classic ultrasonographic findings in the thyroid itself or positive biochemical parameters such as anti–thyroid peroxidase or anti-thyroglobulin antibodies. Moreover, this understanding may prevent undesired clinical tangents pursuing possible malignancies by multiple or repeated fine-needle biopsies or thyroglobulin washings of benign inflammatory lymph nodes based solely on an increased number of mildly enlarged benign-appearing cervical lymph nodes in the setting of CAT.

Benign lymph nodes typically have a characteristic appearance on ultrasound (7). Not every lymphadenopathy requires a routine and/or an immediate biopsy. In cases of growth, demonstrated on serial exams, or persistent enlargement over time, consideration should be given to fine-needle biopsy with a thyroglobulin level determined on needle washing. If the biopsy material is insufficient to provide interpretable data by cytology or flow cytometry, and morphologic features on ultrasound are still suspicious, consideration might be given to an open nodal excisional biopsy. This should be an infrequent event in CAT patients. Clinical management would then be instituted based on pathological data.

While the findings of this study clearly document that CAT can be associated with cervical lymphadenopathy, it is important to be cautious when significantly abnormal lymph nodes are detected (such as lymph nodes with increased size or a morphology suggestive of malignancy) because these could represent a malignant process developing in the setting of CAT. In addition to the possibility of metastases from a thyroid cancer derived from follicular cells, there is an association between Hashimoto's thyroiditis and lymphoma, particularly originating in or involving the thyroid gland (8).

Brancato et al. (4) are to be congratulated for investigating this phenomenon and bringing their data into the scientific literature. Hopefully, a greater appreciation for the size, distribution, and morphology of what are presumed to be benign lymph nodes in patients affected by CAT will prevent many patients and providers from embarking on unnecessary tangents in diagnosis and treatment.