Paraganglioma-like medullary thyroid carcinoma: fine needle aspiration cytology features with histological correlation
Abstract
Two cases of an extremely rare paraganglioma-like variant of medullary thyroid carcinoma(MTC) are reported.The cytological smears contained predominantly ovoid to spindled epithelial cells arranged in cohesive three-dimensional clusters with sharp margins; isolated individual cells were rare.No colloid or amyloid was present in the background. Tumour cells showed significant nuclear atypia with occasional bizarre and binucleated cells.
Their chromatin was coarse, granular, sometimes with grooves and intranuclear inclusions. Calcitonin was demonstrated in case 2.
Histology confirmed paraganglioma variant of MTC in both cases. Mutation of RET proto-oncogene in exon 16 (Met918Thr) - germline in case 2 and somatic in case 1 was detected by DNA sequencing in both cases.This is the first report of cytological findings in the paraganglioma-like variant of MTC.
Despite its rarity, it can be reliably diagnosed by FNAC.