Endocrine Abstracts

Introduction: Primary thyroid lymphoma is a rare entity accounting for <5% of thyroid malignancies and <2% of extra-nodal lymphomas with diffuse large B-cell lymphoma (DLBCL) being the most common subtype. Plasmablastic lymphoma (PBL) is an uncommon and aggressive subtype of DLBCL mainly detected in patients with immunosuppression, especially related to HIV infection. Typically, PBL occurs in extra-nodal sites, usually the oral cavity and the gastrointestinal tract while primary thyroid PBL is extremely rare.

Objective: To report an extremely rare case of extra-nodal PBL presented as a rapidly increasing thyroid mass.

Case presentation: A 73-year-old male with a history of multinodular goiter and autoimmune thyroiditis, presented to the emergency department with a rapidly growing, painless, cervical mass and dyspnea. Computed tomography (CT) scan revealed an enlarged heterogenous thyroid gland (12 cm right lobe, 10 cm left lobe), causing trachea compression and displacement to the left side. Fine needle aspiration (FNA) cytology suggested an undifferentiated thyroid cancer and a core biopsy was performed to confirm the diagnosis. However, histological examination revealed the presence of a PBL with expression of Vimentin, LCA, CD79a, slgk, CMyC (in 35% of the tumor cells), while staining for TTF1 and TG was negative; cell proliferation index Ki-67 of 50% was found. Bone marrow biopsy showed no lymphoma cells infiltration, but whole body CT scan showed stage IV disease (multiple subcutaneous nodules, as well as abdominal and inguinal lymphadenopathy). Thyroid function was normal (TSH 1.71 μIU/ml, fT4 15.07 pmol/L, NR 9-19), while anti-TPO and anti-Tg were positive (>2000 IU/ml, NR <5.6 and 143.32 IU/ml, NR <4, respectively). Virology testing for HIV was negative. Treatment with systemic chemotherapy DA-EPOCH (dose adjustment etoposide, prednisolone, vincristine, cyclophosphamide and doxorubicin) was initiated with ≥30% decrease of the longest diameter of the thyroid masses after the completion of 3 cycles of chemotherapy. Compression of the trachea was significantly decreased and the patient does not experience any dyspnea.

Conclusion: To our knowledge, this is the third documented case of primary thyroid PBL. Due to its rarity, primary thyroid lymphoma can be challenging to diagnose and it should always be suspected in patients with a rapidly enlarging cervical mass. FNA is often insufficient for diagnosis and a core biopsy with histological confirmation is necessary to differentiate thyroid lymphoma from anaplastic thyroid cancer. Early and appropriate treatment can lead to significant patient’s response and outcome improvement.