What is the pathology of follicular carcinoma in patients with thyroid cancer?

Updated: May 14, 2020
  • Author: Pramod K Sharma, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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On gross pathology, the tumors appear as round, encapsulated, light brown neoplasms. Fibrosis, hemorrhage, and cystic changes are found in the lesions. Under microscopy, the tumors contain neoplastic follicular cells, which overall can have a solid, trabecular, or follicular growth pattern (that usually produces microfollicles). The follicular cells in these tumors do not have characteristic features like papillary carcinoma cells.

Follicular carcinomas are differentiated from benign follicular adenomas by tumor capsule invasion and/or vascular invasion. For this reason, differentiating follicular adenomas from follicular carcinomas is extremely difficult with FNAB cytology and frozen section analysis. The tumors are divided into minimally invasive and widely invasive lesions depending on the histologic evidence of capsule and vascular invasion. Immunohistochemical staining for thyroglobulin and cytokeratins is nearly always positive.

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