Anaplastic large cell lymphoma: a potential pitfall in the differential diagnosis of melanoma

Arch Pathol Lab Med. 2013 Feb;137(2):280-3. doi: 10.5858/arpa.2011-0532-CR.


The diagnosis of metastatic melanoma can be complicated by absent characteristic cytology, melanin, or antigen expression in a suspect tumor, putting the pathologist at risk for incorrectly diagnosing recurrent melanoma while missing a second malignancy. We report a 69-year-old man with a history of acral melanoma, metastatic to inguinal nodes, presenting with an ipsilateral thigh nodule. Histology showed a proliferation of pleomorphic cells in the dermis and subcutis, suspicious for melanoma. S100, Melan-A, and HMB-45 immunohistochemistry were negative. However, microphthalmia-associated transcription factor and CD117 labeled the neoplasm, prompting consideration of a late metastatic melanoma with loss of antigen expression. Subsequent immunolabeling for CD4, CD43, and CD30 and clonal T-cell gene rearrangements enabled the correct diagnosis of cutaneous anaplastic large cell lymphoma. This case illustrates a pitfall in evaluating tumors in patients with known metastatic melanoma, and emphasizes the need for broad-spectrum immunohistochemistry in cases that are not clear-cut.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Diagnosis, Differential
  • Humans
  • Immunohistochemistry
  • Ki-1 Antigen / metabolism
  • Lymphoma, Large-Cell, Anaplastic / diagnosis*
  • Lymphoma, Large-Cell, Anaplastic / metabolism
  • Lymphoma, Large-Cell, Anaplastic / pathology
  • Male
  • Melanoma / diagnosis*
  • Melanoma / metabolism
  • Melanoma / pathology
  • Melanoma / secondary
  • Microphthalmia-Associated Transcription Factor / metabolism
  • Proto-Oncogene Proteins c-kit / metabolism
  • Skin Neoplasms / diagnosis*
  • Skin Neoplasms / metabolism
  • Skin Neoplasms / pathology


  • Ki-1 Antigen
  • MITF protein, human
  • Microphthalmia-Associated Transcription Factor
  • Proto-Oncogene Proteins c-kit