August 2018

  • Patient Information
    • 40 year old male presented with a 2.4 cm mass on the forearm.
  • Clinical Diagnosis
    • Cyst
    • Lipoma
  • Histology

    Sections show a well-circumscribed neoplasm based within the subcutaneous tissue.

    Higher magnification shows the neoplasm is composed of numerous osteoclast-like giant cells and similar-appearing mononuclear cells.

  • Final Diagnosis

    Giant cell tumor of tendon sheath

    • Giant cell tumor of tendon sheath is a benign soft tissue neoplasm that typically arises during the third to fifth decades of life
    • These tumors present as painless, firm, slow growing masses that often occur on the volar aspects of the hands and feet, most commonly near the distal interphalangeal joint
    • Histopathology reveals a well-circumscribed nodule based within the deep dermis or subcutaneous tissue composed of numerous osteoclast-like giant cells and mononuclear cells with similar-appearing nuclei
      • Histiocytes containing hemosiderin and lipid are also commonly present
      • The tumor cells are positive for CD68 by immunohistochemistry
    • Surgical excision is curative but approximately 25% of cases may locally recur
  • Summary
    • Giant cell tumor of tendon sheath is a benign soft tissue neoplasm
    • These tumors present as painless, firm, slow growing masses that often occur on the volar aspects of the hands and feet
    • Histopathology reveals a well-circumscribed nodule based within the deep dermis or subcutaneous tissue composed of numerous osteoclast-like giant cells and mononuclear cells with similar-appearing nuclei
    • Surgical excision is curative but approximately 25% of cases may locally recur