High-grade B-cell Non-Hodgkin's Lymphoma Masquerading as Thyroid Carcinoma; a Case Report.

Introduction: High grade B-cell lymphoma and diffuse large B cell exhibiting myelocytoma (MYC) translocation with B-cell lymphoma 2 (BCL2) and/or B-cell lymphoma 6 (BCL6) re-arrangements, also known as double and triple hit lymphomas, are aggressive entities. World Health Organization update 2017 includes this cytogenetically defined category of "High grade B cell lymphoma with myelocytoma MYC and BCL2 and/ or BCL6 rearrangements" as a distinct entity on their own. We present an interesting case of an obese patient presenting with a neck mass, suspected to be an aggressive thyroid carcinoma, which eventually turned out to be a high grade B-cell lymphoma.

Case description: A 64 years-old male presented with complaints of neck pain for 10 weeks and a huge swelling in front of neck for 4 weeks. Respiratory system evaluation revealed cough, pleuritic pain and expectoration. Rest of the systemic review was unremarkable. Baseline reports showed hypothyroid status. Ultrasonography (USG) thyroid showed right upper pole Thyroid Imaging Reporting and Data Systems - 4 (TIRADS-4) nodule with bilateral cervical lymphadenopathy for which correlation with fine needle aspiration cytology (FNAC) was advised. Magnetic resonance imaging (MRI) films were submitted for review which showed overall features of locally invasive primary thyroid malignancy. Case was discussed in a multi-disciplinary team (MDT) meeting and suspicion arose of non-thyroidal origin of tumor. Patient underwent Positron emission tomography/computed tomography (PET/CT) as per MDT recommendations. PET/CT findings were highly suggestive of lymphomatous disease as opposed to thyroidal malignancy suspicion early on, which was confirmed on histopathology of cervical nodes.

Practical implications: High grade B-cell lymphoma is an aggressive entity and can be very deceptive in its presentation, as evident from this case report. Functional imaging modalities such as Fluorodeoxyglucose (F-18 FDG) PET/CT can provide crucial assistance in unmasking a deceptive disease entity masquerading as some other, thus changing the management plan completely.