Histology Course A IV 30 Department of Pathology, University of Zurich Histokurs

A IV 30

lymph node metastasis of a malignant melanoma of the skin  IHC: S-100  
  ICD-10: C77.4, C44.9; ICD-O: 8720/6, 8720/3
An inguinal lymph node of the patient of slide A II 8 is shown (description of the primary skin lesion see slide A II 8)
- The lymph node is permeated by large groups of cells staining intensely for the melanocytic marker S-100.
- In contrast to metastases from carcinomas, melanomas generally do not stain for cytokeratins. Melanoma cells are strongly positive for vimentin and more than 90% stain positive for S-100. In addition, melanoma cells may stain for melan-A and HMB-45.
- Malignant melanoma may mimic a variety of tumors. Still, immunohistochemistry together with the histological appearance usually allows diagnosis of a lymph node metastasis of a malignant melanoma.