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Malignant peripheral nerve sheath tumour-like primary cutaneous malignant melanoma
  1. J Cruz1,
  2. J S Reis-Filho2,
  3. J M Lopes3
  1. 1Department of Pathology, Hospital São João, 4202-451 Porto, Portugal
  2. 2The Breakthrough Toby Robins Breast Cancer Research Centre, Institute of Cancer Research, London SW3 6JB, United Kingdom
  3. 3IPATIMUP—Institute of Molecular Pathology and Immunology, University of Porto, 4200-465 Porto, Portugal
  1. Correspondence to:
 Dr J M Lopes
 R Roberto Frias, S/N, 4200-465-Porto, Portugal;


Malignant melanoma is known for its protean cytomorphological features, architectural patterns, and stromal changes, in addition to its ability to mimic various benign and malignant non-melanocytic tumours. Anecdotal cases of metastatic malignant melanoma simulating soft tissue sarcomas have been reported. Interestingly, this mimicry is more often seen in recurrent lesions and metastatic deposits. This report describes a case of a primary spindle cell cutaneous malignant melanoma with a prominent neural-like fascicular pattern and nuclear palisading, simulating a conventional malignant peripheral nerve sheath tumour (MPNST). Clinical, microscopic, and immunohistochemical features of the different entities included in the differential diagnosis of cutaneous spindle cell malignant tumours, such as MPNST, atypical fibroxanthoma, and spindle cell squamous cell carcinoma are discussed. Of note, the presence of an atypical epidermal or junctional component, cell pigmentation, and cell nesting, in addition to diffuse and strong reactivity for S-100 protein and other melanocytic markers, are helpful in the diagnosis of these troublesome lesions.

  • HMB45
  • S-100 protein
  • immunohistochemistry
  • neurofibrosarcoma
  • AFX, atypical fibroxanthoma
  • MITF, microphthalmia associated transcription factor
  • MM, malignant melanoma
  • MPNST, malignant peripheral nerve sheath tumour
  • NF1, neurofibromatosis 1

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