Endocrine Abstracts

Background: Thyroid lymphoma accounts for approximately 2-8% of malignant thyroid masses. Two types are recognized: primary thyroid lymphoma, originating in the thyroid and representing 1-2% of extranodal lymphomas, and secondary thyroid involvement, occurring in 11-27% of cases.

Case presentation: We report the case of a 69-year-old woman referred for dysphagia and anterior cervical discomfort. She reported a palpable left inguinal lymphadenopathy identified four months prior to her presentation. We performed a cervical ultrasound, identifying a partially cystic nodule in the right thyroid lobe, a 10mm hypoechoic isthmic nodule with peripheral vascularity, a 23 mm irregular hypoechoic mass in the left lobe with central vascularity, and multiple left jugulo-carotid lymph nodes (Figure 1.A.). Technetium-99m thyroid scintigraphy showed a nearly absent uptake of the left lobe, corresponding to a hyper-metabolic area on the FDG PET-CT. Fine-needle aspiration (FNA) of the left thyroid nodule revealed inflammatory and hemorrhagic cytology, while biopsy of the inguinal lymph node confirmed the diagnosis of marginal zone lymphoma. PET-CT staging established a stage IVB marginal zone lymphoma. Due to the disseminated disease and clinical symptoms, treatment with Rituximab and Bendamustine was initiated. After four cycles, follow-up thyroid ultrasound no longer revealed the isthmic and the left hypoechoic thyroid masses (Figure 1.B.). The patient also reported clinical improvement including of dysphagia.

Figure 1: (A) Hypoechoic isthmic nodule.(B) Hypoechoic mass in the left lobe of the thyroid gland.(C) One of the jugulocarotid lymph nodes.(D) Left thyroid lobe after four cycles of Rituximab and Bendamustine.

Discussion: The thyroid gland is an uncommon metastatic site for nodal or extranodal lymphomas (1). Hashimoto’s thyroiditis has been linked to an increased risk of primary thyroid lymphoma through chronic lymphocytic stimulation, though this association is less obvious in secondary forms (5). Our patient had a history of Hashimoto’s thyroiditis. Clinically, symptoms related to thyroid infiltration-such as hoarseness or dysphagia-are less frequently observed in secondary thyroid lymphoma (2), which was the case in our patient. Thyroid ultrasound is the first-line imaging tool. Primary lymphoma usually appears as a diffuse hypoechoic area with septations, whereas secondary lymphoma may mimic anaplastic thyroid carcinoma, presenting as a solid hypoechoic mass (3). Internal vascularity and lack of calcification may help differentiate lymphoma from anaplastic thyroid carcinoma; both are often hypermetabolic on FDG PETCT (3). Fine-needle aspiration cytology (FNAC) may be performed, but is often insufficient for diagnosis due to limited sample size and inability to perform immunohistochemistry. Core needle or surgical biopsy is preferred as they preserve tissue architecture (3). Secondary thyroid lymphoma is typically disseminated at diagnosis, in contrast to primary thyroid lymphoma, which tends to remain localized and is associated with a more favorable prognosis (4). Treatment strategy depends on staging; disseminated cases typically require systemic chemotherapy combined with Rituximab (5).

Conclusion: Thyroid involvement in marginal zone lymphoma is rare, but should be considered in patients with thyroid nodules and generalized lymphadenopathy. PET-CT and histopathological confirmation are crucial for accurate diagnosis, staging, and treatment planning. Biopsy is recommended in order to allow immunohistochemical analysis and to preserve tissue architecture, essential for proper classification.

References: 1. Mancuso S, Carlisi M, Napolitano M, Siragusa S. Lymphomas and thyroid: Bridging the gap. Hematol Oncol. 2018 Feb 27. doi: 10.1002/hon.2504. Epub ahead of print. 2. Takashima S, Takayama F, Momose M, Shingu K, Sone S. Secondary malignant lymphoma which simulated primary thyroid cancer. Clin Imaging. 2000 May-Jun;24(3):162-5. doi: 10.1016/s0899- 7071(00)00195-9. 3. Sharma A, Jasim S, Reading CC, Ristow KM, Villasboas Bisneto JC, Habermann TM, Fatourechi V, Stan M. Clinical Presentation and Diagnostic Challenges of Thyroid Lymphoma: A Cohort Study. Thyroid. 2016 Aug;26(8): 1061-7. doi: 10.1089/thy.2016.0095. 4. Nam M, Shin JH, Han BK, Ko EY, Ko ES, Hahn SY, Chung JH, Oh YL. Thyroid lymphoma: correlation of radiologic and pathologic features. J Ultrasound Med. 2012 Apr;31(4):589-94. doi: 10.7863/jum.2012.31.4.589. 5. Stein SA, Wartofsky L. Primary thyroid lymphoma: a clinical review. J Clin Endocrinol Metab. 2013 Aug;98(8):3131-8. doi: 10.1210/jc.2013-1428.