Collision tumour of thyroid – A case series

Abstract

A collision tumour is described as the coexistence of two adjacent but histologically distinct and morphologically independent malignant tumours in the same organ with no histological admixture. In this article we present 3 cases of simultaneous occurrence of two thyroid neoplasm in the same patient. A 49 year old lady with swelling in right lobe of thyroid, diagnosed as follicular neoplasm with hurthle cell morphology (Bethesda category IV) on Fine needle aspiration cytology (FNAC). Histopathological examination (HPE) showed Hurthle cell carcinoma, right lobe and 3 mm foci of NIFTP, left lobe. Another 45 year old lady with bilateral thyroid swelling diagnosed as hurthe cell neoplasm (Bethesda category IV), left lobe and suspicious of papillary thyroid carcinoma, right lobe on FNAC. HPE showed papillary thyroid carcinoma, classical variant in the right lobe with a focus of papillary carcinoma in the isthmus and hurthle cell adenoma in left thyroid. A 27 year old man with thyroid swelling revealed medullary carcinoma in FNAC. Final histopathological diagnosis was medullary carcinoma, right lobe of thyroid and isthmus, papillary carcinoma (micropapillary variant) in pyramidal lobe along with metastatic medullary carcinoma in right level II lymph nodes and metastatic medullary and papillary carcinoma in central compartment nodes. Collision tumors are a diagnostic as well as therapeutic challenge due to the dual pathology. Extensive sampling should be done as co-existence of different neoplasms can occur.