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Expression of Calretinin and the alpha-Subunit of Inhibin in Granular Cell Tumors

Samson W. Fine MD, Maomi Li MD, PhD
DOI: http://dx.doi.org/10.1309/GRH4JWX6J9J7QQTA 259-264 First published online: 1 February 2003

Abstract

Granular cell tumors (GCTs) typically express S-100 protein, which has been used as a marker in differential diagnosis. Calretinin, a calcium-binding protein related structurally to S-100, and inhibin, a polypeptide hormone secreted primarily by ovarian granulosa cells and testicular Sertoli cells and functioning as an inhibitor for pituitary follicle-stimulating hormone secretion, are potentially useful but not well-evaluated markers for GCTs. We studied 43 cases of GCT with antibodies to calretinin, the inhibin alpha-subunit, and S-100 protein. All tumors were positive for inhibin alpha-subunit and S-100 protein, with 50% or more cells showing moderate to strong staining. Forty tumors (93%) were positive for calretinin, ranging from focal weak to diffuse strong staining. Enhanced staining for calretinin in the tumor cells adjacent to hyperplastic squamous epithelium was observed in 9 of 13 cases showing pseudoepitheliomatous hyperplasia. Calretinin and the inhibin alpha-subunit are useful markers for GCTs. The expression of calretinin, a primarily neuronal protein, in GCTs further supports its neural differentiation or derivation. The elevated calretinin expression in the tumor cells adjacent to the hyperplastic squamous epithelium suggests a role for calretinin in the tumor cells–squamous epithelium interaction.

Key Words:
  • Granular cell tumor
  • Calretinin
  • alpha-Inhibin
  • Schwann cells