Poorly differentiated (insular) thyroid carcinoma arising in a long-standing colloid goitre: A cytological dilemma

Poorly differentiated (insular) thyroid carcinoma (PDITC) is an uncommon thyroglobulin producing neoplasm intermediate in aggressiveness between well-differentiated carcinomas of follicular cell origin and undifferentiated anaplastic carcinoma. Its cytomorphological recognition is essential for planning surgery and subsequent management as it is known for its aggressive behavior, advanced stage at presentation, local recurrences and rapid dissemination. We report a case of PDITC arising in a long-standing goiter, in which presence of microfollicular structures and minimal necrosis resulted in difficulty in distinguishing it from a follicular neoplasm of thyroid.