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Melan A (MART-1)

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  • Melan-A (A103) highlights the invasion in this melanoma.
  • Melan A expression in scattered cells in a pigmented neurofibroma.
  • Melan A expression in scattered cells in a pigmented neurofibroma.
  • Melan A expression in a cellular blue nevus.

Melan A is an antigen expressed by melanocytes.


  • A103[1]
  • Melan A
  • Mart-1


Technical InfoEdit

Staining PatternEdit

  • Cytoplasmic

Expression in Normal TissuesEdit

  • Normal Melanocytes
  • Adrenal cortex

Expression in Neoplastic EntitiesEdit

Tumor name % Positive Staining Number of Cases
Adrenocortical adenoma: 100%[2] (15/15)[2]
Benign melanocytic nevus
Blue nevus

Intermediate/Uncertain Malignant PotentialEdit
Tumor name % Positive Staining Number of Cases
Sertoli-Leydig cell tumor of ovary[1]
PEComas (angiomyolipoma, lymphangioleiomyomatosis, etc) 72%[3] 13/18[3]
Leydig cell tumor of testis[1]

Tumor name % Positive Staining Number of Cases
Adrenocortical carcinoma 75%[2] 9/12[2]
Clear Cell Sarcoma 71%[4] 23/32[4]
Pleomorphic liposarcoma, epithelioid variant 67%[5] 4/6[5]
Single reported case of Mart-1 expression by serous carcinoma of ovary [6]

Expression in Non-Neoplastic EntitiesEdit

Pertinent NegativesEdit

This immunostain is typically NEGATIVE in the following entities:

  • Pheochromocytoma: Negative in 89% (16/18)[2]
  • Paraganglioma: Negative in 95% (18/19)[2]

Practical Uses / PanelsEdit

  • Melan A is superior to S100 when evaluating sentinel lymph nodes for Melanoma since S100 stains nonmelanoma cells in the lymph node.[7]

Common PitfallsEdit

  • Epithelioid pleomorphic liposarcoma may express Melan A, a finding that could potentially lead to a misdiagnosis of metastatic adrenocortical carcinoma.[5]


  1. 1.0 1.1 1.2 Am J Surg Pathol. 1998 Jan;22(1):57-63.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 Mod Pathol 2003;16(6):591–597
  3. 3.0 3.1 Am J Surg Pathol. 2005 Dec;29(12):1558-75.
  4. 4.0 4.1 Am J Surg Pathol. 2008 Mar;32(3):452-60.
  5. 5.0 5.1 5.2 Ultrastructural Pathology 2002, Vol. 26, No. 5 , Pages 299-308
  6. Archives of Pathology & Laboratory Medicine: February 2002, Vol. 126, No. 2, pp. 170-172.
  7. J Surg Pathol. 2001 Aug;25(8):1039-46.

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