Cartilaginous metaplasia of thyroid nodule

Adenomatous goiter is the most common form of thyroid disease. Although degenerative changes like fibrosis, calcification, cystic changes and hemorrhagic tissue are commonly found, cartilaginous metaplasia is an unusual phenomenon in the thyroid gland. Heterotopic cartilage formation is a very rare finding in both neoplastic and non-neoplastic lesions. Only 2 cases have been reported so far. Here we present a case of a 65-year-old female who presented with a midline swelling in her neck for 2 months associated with difficulty in swallowing. The lymph nodes were not palpable and there were no pressure symptoms. Ultrasonography was suggestive of thyromegaly with large goiterous change in left lobe and isthmus of thyroid. Fine Needle Aspiration Cytology (FNAC) revealed Bethesda Category I lesion. The patient underwent left hemi-thyroidectomy. Microscopy revealed encapsulated lesions composed of variable-sized follicles filled with colloid. Cystic areas lined by benign follicular cells showing foci of cartilage were also observed. Consistent with diagnosis of adenomatoid goiter with cartilaginous metaplasia. This case shows a rare histopathological change in the thyroid nodular lesions.