Malignant epithelioid schwannoma of the skin showing partial HMB-45 positivity

Am J Dermatopathol. 1993 Aug;15(4):378-84. doi: 10.1097/00000372-199308000-00017.

Abstract

A malignant epithelioid schwannoma occurred on the right second toe of a 30-year-old Japanese man. It was a firm, flesh-colored, benign-appearing nodule and measured 13 x 9 mm in diameter and 6 mm in height. To our knowledge, this is the first case of malignant epithelioid schwannoma occurring on the toe. Histopathology was characterized by a circumscribed nodule in the dermis that predominantly consisted of atypical large epithelioid cells with some spindle cells whose proliferation was similar to that of the Verocay bodies seen in ordinary schwannoma. Fontana-Masson staining demonstrated no melanin pigment in the tumor at the light microscopic level. The eosinophilic cytoplasm contained abundant glycogen and was positive for S-100 protein and HMB-45, as usually seen in melanomas. Electron microscopy revealed that there was an abundance of long-spacing collagen in the extracellular matrix, and the cells contained numerous dense-cored granules. But no definite melanosomes were observed in any stage. As far as we are aware, this is the first case of a malignant epithelioid schwannoma showing HMB-45 positivity.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Antigens, Neoplasm / analysis*
  • Cytoplasm / ultrastructure
  • Epidermis / pathology
  • Foot Diseases / pathology*
  • Glycogen / analysis
  • Humans
  • Male
  • Neurilemmoma / pathology*
  • Organelles / ultrastructure
  • S100 Proteins / analysis
  • Skin Neoplasms / pathology*
  • Toes / pathology
  • Vimentin / analysis

Substances

  • Antigens, Neoplasm
  • S100 Proteins
  • Vimentin
  • Glycogen