Abstract

Primary malignant lymphoma of the thyroid gland is uncommon malignancies. Its fine needle aspiration cytology (FNAC) findings are rarely described in the literature. This article highlights the FNAC diagnosis of primary malignant lymphoma of the thyroid gland. A 70-year-old female presented with a rapidly enlarging thyroid mass of five months' duration. FNAC smears showed low cellularity consisting of predominantly atypical enlarged lymphoid cells admixed with a few small lymphocytes, plasma cells, and oncocytic cells. Some disrupted lymphoid cells were also present. The tumor cells infiltrated into the thyroid follicular epithelium forming lymphoepithelial lesion. The cytologic appearance showed a diffuse mixture of cell types with only a few small, mature lymphocytes and many enlarged lymphoid cells. The enlarged lymphoid cells were atypical and pleomorphic with nuclear clefting and irregularities. Grossly, the left lobe of the thyroid was nearly replaced by a diffuse firm to soft solid mass with smooth tan fish-flesh homogeneous cut surface. Histological diagnosis was diffuse large B-cell lymphoma with areas of marginal zone B-cell lymphoma of MALT type.

• Keywords: Fine needle aspiration cytology (FNAC);Thyroid gland;Primary malignant lymphoma;