Primary Thyroid Lymphoma: How Molecular Biology and Ancillary Techniques Can Help the Cytopathologist Overcome This Diagnostic Challenge

Primary thyroid lymphoma (PTL) occurs rarely, its diagnosis is a challenge, and the prognosis of these patients depends on the time of diagnosis. Even though fine-needle aspiration cytology (FNAC) is recognized as the most accurate tool for detecting thyroid malignancies, its sensitivity for PTL is poor. Both clinical and ultrasound presentation of PTL can be atypical, and laboratory tests fail to furnish relevant data. Consequently, the reliability of a cytopathologist facing PTL can be poor, even when he is aware of its clinical information. In addition, the cases described in the literature are extremely rare and fragmentary, and consequently, the molecular data currently available for this neoplasm are practically negligible. Here, we present a case report in order to discuss the intrinsic limitations in achieving a final diagnosis of PTL and how using molecular diagnostics to identify potential mutational models can improve the evaluation of this neoplasm.