An Evaluation of CD61 Immunohistochemistry in Identification of Vascular Invasion in Follicular Thyroid Neoplasms

Head Neck Pathol. 2020 Jun;14(2):399-405. doi: 10.1007/s12105-019-01048-8. Epub 2019 Jun 19.


The identification of vascular invasion in follicular thyroid neoplasms is essential for categorizing lesions as benign (follicular adenomas) or malignant (follicular thyroid carcinomas). Among the histologic criteria diagnostic of true vascular invasion is tumor-cell associated thrombosis, including fibrin deposition and platelet clumping. This study aims to evaluate whether an immunohistochemical stain for the platelet-associated protein CD61 could assist in identifying tumor-associated thromboses and thereby confirm vascular invasion in follicular thyroid neoplasms. Histologic review and CD61 immunostaining of 19 atypical follicular adenomas, 13 non-metastatic follicular thyroid carcinomas, and 11 metastatic follicular thyroid carcinomas was performed. Linear arrays or clustered groups of CD61-expressing intravascular platelets were present in 51% of cases overall, including 54% of follicular thyroid carcinomas and 47% of follicular adenomas, mostly within intracapsular or peritumoral vessels. In three follicular thyroid carcinomas (all with distant metastases), CD61-expressing platelets were present in association with intravascular tumor cells. This finding was not present in adenomas. CD61 staining alone did not distinguish between atypical follicular adenomas, non-metastatic carcinomas, and metastatic carcinomas. When present in association with intravascular tumor cells, however, CD61-expressing platelets may serve as a marker for vascular invasion and aid in the diagnosis of follicular thyroid carcinoma.

Keywords: Angioinvasion; Atypical follicular adenoma; CD61; Fibrin; Follicular thyroid carcinoma; Platelets; Thrombi; Vascular invasion.

MeSH terms

  • Adenocarcinoma, Follicular / pathology*
  • Adenoma / pathology*
  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Biomarkers, Tumor / analysis*
  • Blood Platelets / metabolism
  • Female
  • Humans
  • Immunohistochemistry
  • Integrin beta3 / analysis*
  • Male
  • Middle Aged
  • Neoplasm Invasiveness / pathology
  • Neoplastic Cells, Circulating / pathology
  • Thyroid Neoplasms / pathology*
  • Young Adult


  • Biomarkers, Tumor
  • ITGB3 protein, human
  • Integrin beta3