Primary Plasmablastic Thyroid Lymphoma: A Case Report

Objective: Primary thyroid lymphoma (PTL) is a rare cause of thyroid cancer. The underlying pathology and subtype of lymphoma are critical to define and prognosticate the tumor. More importantly, solidifying the pathology directs the specific treatment plan for the patient. The aim of this case report was to highlight the importance of histology for treatment and prognosis in PTL. Methods: We report a unique case of PTL in an 80-year-old female who presented to the endocrinology clinic with an enlarging goiter. Results: Initial fine-needle aspiration did not reveal malignancy. Surgical biopsy soon after revealed plasma-blastic lymphoma, which is an aggressive type of B-cell lymphoma, and the patient was promptly referred to hematology and oncology. Plasmablastic lymphoma is a rare form of lymphoma commonly presenting as a mass lesion of the head and neck region, with highest incidence in human immunodeficiency virus (HIV)-positive patients, for which treatment options are limited given its rarity. To our knowledge, there have been no reported cases of the thyroid as the primary location of plasmablastic lymphoma in the United States. In addition, testing was negative for HIV in our patient. Conclusion: The underlying pathology of PTL is vital, as it reveals the specific prognosis and treatment considerations. When a patient presents with an enlarging goiter and PTL is considered, caution should be taken with a negative or equivocal fine-needle aspiration biopsy. Core-needle or surgical biopsy should be done promptly to expedite referral to hematology and oncology and subsequent treatment. Abbreviations: DLBCL diffuse, large, B-cell lymphoma FNA fine-needle aspiration HIV human immunodeficiency virus MALT mucosa-associated lymphoid tissue PET positron emission tomography PTL primary thyroid lymphoma TPO thyroperoxidase