July 2018

  • Patient Information
    • 38 year old female presented with a 2 cm mass on her abdomen.
  • Clinical Diagnosis
    • Cyst
    • Dermatofibroma
  • Histology

    Sections show sheets of epithelioid cells with abundant eosinophilic cytoplasm present throughout the dermis

    Higher magnification shows the lesional cells have finely granular cytoplasm

  • Final Diagnosis

    Granular cell tumor

    • Granular cell tumors are bengin neoplasms that often arise in the oral cavity, particularly the tongue, but occur commonly in the skin and subcutaneous tissue
      • These tumors are believed to arise from Schwann cells or a “neural crest-derived peripheral nerve-related cell”
    • Pseudoepitheliomatous hyperplasia can be seen overlying the tumor and may be mistaken for squamous cell carcinoma on superficial biopsies
    • Granular cells tumors are composed of sheets and aggregates of epithelioid cells with abundant eosinophilic and finely granular cytoplasm
      • Large cytoplasmic granules called pustulo-ovoid bodies of Milian are often identified
      • The granularity of the cytoplasm is caused by accumulation of lysozymes
    • The tumor cells are strongly positive for S100 and CD68 by immunohistochemistry; MITF and NKI/C3 can also be positive
    • Malignant transformation is exceedingly rare but such tumors may metastasize
    • Surgical excision is curative for benign lesions
      • Some lesions may locally recur even with clear margins
  • Summary
    • Granular cell tumors are bengin neoplasms that often arise in the oral cavity, particularly the tongue, but occur commonly in the skin and subcutaneous tissue
    • Granular cells tumors are composed of sheets and aggregates of epithelioid cells with abundant eosinophilic and finely granular cytoplasm
    • The tumor cells are strongly positive for S100 and CD68 by immunohistochemistry; MITF and NKI/C3 can also be positive
    • Surgical excision is curative for benign lesions