# Primary Follicular Lymphoma of Thyroid: A Rare Case Report with Review of the Literature

## TL;DR

This paper presents a rare case of primary follicular lymphoma of the thyroid and highlights the importance of accurate diagnosis using histopathology and immunohistochemistry.

## Contribution

The paper adds to the limited literature on primary follicular lymphoma of the thyroid and emphasizes the need for immunohistochemical confirmation for accurate diagnosis.

## Key findings

- A 62-year-old female was diagnosed with primary follicular lymphoma of the thyroid after histopathological and immunohistochemical assessments.
- CD20, CD10, BCL2, and BCL6 positivity in lymphoid follicles helped confirm the diagnosis.
- FDG-PET CT scan showed no evidence of lymphoma elsewhere, supporting the primary nature of the thyroid lymphoma.

## Abstract

Thyroid lymphomas are predominantly secondary to lymphoma at other sites, and primary follicular lymphoma of the thyroid is a very rare entity.

Here, we report a case of a 62-year-old female who presented with swelling in the front of her neck for one month. The clinical diagnosis was a multinodular goiter. Fine needle aspiration cytology was done and reported as nodular colloid goiter with lymphocytic thyroiditis. The system examination was unremarkable. Histopathological assessments of the right hemithyroidectomy specimen revealed the effacement of thyroid architecture by abnormal and extensive lymphoid follicles. Immunohistochemistry revealed CD20, CD10, BCL2, and BCL6 positivity in the lymphoid follicles. FDG-PT CT scan demonstrated no evidence of lymphoma elsewhere. So, a e final diagnosis of follicular lymphoma of the thyroid was made.

Due to the rarity and low prevalence of primary follicular lymphoma of the thyroid and challenging in its differentiation from Hashimoto's thyroiditis with dense lymphoplasmacytic infiltration and formation of lymphoid follicles, histopathologic diagnosis should be confirmed by immunohistochemical studies.