A Benign Lesion of Thyroid Masquerading as a Salivary Gland Malignancy on Cytology.

INTRODUCTION: Thyroid lesions are one of the most common diseases observed in clinical practice in the North India. These diseases have distinct cytological morphology and thus FNAC is done frequently. Here we report a case of adenomatoid goitre mimicking adenoid cystic carcinoma (ACC) of salivary gland on cytology. Such close resemblance on morphology makes this a case of unusual morphological presentation of a very common condition.

CASE SUMMARY: We report here a case of a 60-year-old female who developed a right anterior neck swelling six years back. Systemic clinical findings were unremarkable. Routine laboratory investigations, including thyroid function test were within normal limits. A High-resolution ultrasound of neck was performed, and a TIRADS-IV lesion measuring 28.8 × 22.9 mm was reported. Fine needle aspiration was done. Seven smears were made and stained with MGG, H&E and PAP stains. Smears were moderately cellular and abundant globular, amorphous material was observed with lesional cells forming three-dimensional rosette-like structures around them, producing an ACC-like pattern. A second consultation and immunohistochemistry on cell block we performed which led to a diagnosis of adenomatoid goitre, confirmed later histologically.

CONCLUSION: Benign lesions of thyroid can sometime mimic adenoid cystic carcinomas of salivary glands. Misdiagnosing any such case based solely on morphology can lead to wrong prognostication and thus wrong treatment. Extensive review of literature and a second consultation with an experienced pathologist should be done. Whenever needed a cell block preparation and a complete immunohistochemistry panel should be performed.