MON-404 - Papillary Thyroid Carcinoma Coexisting with Thyroid Tuberculosis: A Case Report

Thyroid tuberculosis is a rare condition even in endemic countries, accounting for less than 1% of all cases of extrapulmonary tuberculosis, and its coexistence with Papillary Thyroid Carcinoma (PTC) is extremely rare, posing unique diagnostic and therapeutic challenges.

We present the case of a 45 year old female who initially presented with a right lateral neck mass ~1x1cm with no associated symptoms. Neck ultrasound revealed multiple thyroid nodules, with a 1.0x1.0x0.7cm hypoechoic solid nodule, right side of isthmus (TI-RADS 5), alongside multiple enlarged cervical lymph nodes. Fine needle aspiration biopsy (FNAB) of the thyroid nodule was suspicious for PTC (Bethesda V), while FNAB of the cervical lymph nodes was negative for malignant cells. She underwent total thyroidectomy with right neck dissection. Postoperatively, she experienced transient hypocalcemia managed with calcium and vitamin D supplementation. Histopathology revealed PTC, classic subtype, right inferior thyroid lobe and isthmus, and chronic granulomatous inflammation with Langhans giant cells and caseation necrosis, confirming tuberculous thyroiditis and lymphadenitis. This unexpected diagnosis led to referral to Infectious Disease specialists and initiation of anti-Koch's treatment. The patient also received Radioactive Iodine (RAI) therapy weeks postoperatively and subsequently started on hormone replacement therapy with Levothyroxine.

The coexistence of thyroid tuberculosis (TB) and PTC is extremely rare, with only a few reported cases in medical literature. Clinical presentation of thyroid tuberculosis often resembles thyroid malignancy hence the overlapping clinical features make diagnosis challenging. FNAB is useful but may not be sufficient, as caseating granulomas may not always be present in cytologic samples. Most cases of thyroid TB are diagnosed based entirely on postoperative histopathological examination. While total thyroidectomy was appropriate for PTC, postoperative management required a multidisciplinary approach.

This case highlights the diagnostic challenge of coexisting thyroid tuberculosis and malignancy, emphasizing the need for thorough histopathologic evaluation. Although rare, the dual occurrence of thyroid tuberculosis and PTC must be considered in patients presenting with thyroid nodules and cervical lymphadenopathy, especially in tuberculosis-endemic regions. A comprehensive diagnostic approach that includes ultrasound, FNAB, and histopathology is essential for accurate diagnosis and proper management.

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