Primary Thyroid Lymphoma: A Case Series

Abstract

Background Primary thyroid lymphoma (PTL) is a rare form of thyroid cancer. It is frequently accompanied by Hashimoto's thyroiditis. Treatment approaches differ significantly from those used for other types of thyroid cancer. This study aimed to examine the clinical presentation, diagnostic methods, and treatment strategies employed in patients with PTL. Materials and methods We present a retrospective case series of seven patients diagnosed with PTL at a tertiary care hospital between 2017 and 2021. Results Our sample included seven patients, five (71.4%) females and two (28.6%) males. The mean age was 57.8, and their ages ranged from 39 to 77. Four of our patients were diagnosed with Hashimoto's thyroiditis. Most of the patients presented with a rapidly enlarging mass associated with compression symptoms. The diagnosis of PTL was made by core needle biopsy and surgical excision. They all had diffuse large B-cell lymphoma (DLBCL) in the histopathological examination. Out of the total patients, 28.6% (two patients) experienced mortality: one in stage III and one in stage IV. Conclusion Any patient presenting with a rapidly growing thyroid mass accompanied by a history of Hashimoto's thyroiditis should raise the possibility of PTL. In our retrospective case series, DLBCL was identified as the predominant subtype. Fine-needle aspiration cytology (FNAC) demonstrated limited diagnostic modalities, with none of the cases achieving a definitive diagnosis. In contrast, core needle biopsy was the preferred diagnostic tool. Surgery plays a limited role and is mainly for diagnosis. Prognosis depends on the stage of the disease at diagnosis.

Keywords: chemotherapy (ct); core needle biopsy; hashimoto's thyroiditis; primary thyroid lymphoma (ptl); radiotherapy (rt).

Figure 1. Ultrasound findings

(A) The right is almost totally replaced by a large heterogeneous, hypoechoic lesion with evident vascularity and irregular outline. (B) Diffuse enlargement of the thyroid gland with ill-defined margins and possible retrosternal extension, showing heterogeneous echotexture with multiple variable-sized nodules. (C) Heterogeneous mass lesion, mainly hypoechoic, occupying most of the right thyroid lobe and showing minimal internal color flow. (D) Enlarged right lobe of the thyroid gland noted with a complex cystic nodule having internal echoes. (E) Both thyroid lobes are diffusely markedly enlarged and heterogeneous with multiple hypoechoic small nodules. (F) Large heterogeneous nodule seen occupying and enlarging the left thyroid gland. (G) Enlarged right thyroid lobe and isthmus, nearly totally occupied by a large heterogeneous hypoechoic nodule.

Figure 2. Histopathology selected images of cases

(A) The tumor infiltrates the skeletal muscle fibers (arrow), H&E stain. (B) The tumor is composed of sheets of large cells. No more thyroid follicles are seen in this field, H&E stain. (C) The tumor shows areas of necrosis and numerous apoptotic bodies. (D) The background thyroid shows lymphocytic thyroiditis (arrow), H&E stain. (E) Tumor cells are positive for the B-cell marker CD20. (F) This case showed high Ki-67 proliferation index (more than 90% of nuclei are positive).