Premium
High prevalence of Mi TF staining in undifferentiated pleomorphic sarcoma: caution in the use of melanocytic markers in sarcoma
Author(s) -
Choy Bonnie,
Hyjek Elizabeth,
Montag Anthony G,
Pytel Peter,
Haydon Rex,
Luu Hue H,
Zhen Chao J,
Long Bradley C,
Kadri Sabah,
Segal Jeremy P,
Furtado Larissa V,
Cipriani Nicole A
Publication year - 2017
Publication title -
histopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.626
H-Index - 124
eISSN - 1365-2559
pISSN - 0309-0167
DOI - 10.1111/his.13139
Subject(s) - microphthalmia associated transcription factor , pathology , melanoma , staining , sox10 , immunostaining , biology , immunohistochemistry , medicine , cancer research , transcription factor , gene , genetics
Aims The diagnosis of undifferentiated pleomorphic sarcoma ( UPS ) may be challenging, as other lesions with undifferentiated spindle cell morphology must be excluded, including melanoma. Microphthalmia‐associated transcription factor (Mi TF ) stains naevi and epithelioid melanomas, as well as some mesenchymal neoplasms. The aim of this study was to evaluate the prevalence of Mi TF and melanocytic markers in UPS and a subset of atypical fibroxanthoma ( AFX ). Methods and results Mi TF , SOX 10, Melan‐A, HMB 45 and S100 immunostaining was performed on resection specimens from 19 UPS s and five AFX s. Next‐generation sequencing of 50 genes was performed in UPS s to exclude dedifferentiated melanoma. In 17 of 19 UPS s (89%), tumour cells showed nuclear positivity for Mi TF that was not eliminated by casein block. Three showed focal nuclear staining for HMB 45, which was eliminated by casein block. One showed focal nuclear vacuole staining for S100 with red but not brown chromogen. None expressed SOX 10 or Melan‐A. Mutational analysis of 15 UPS s with adequate DNA showed no mutations within hotspot regions of BRAF , KIT , or NRAS . Four of five AFX s (80%) stained with Mi TF ; other markers were negative. Conclusion There is a high prevalence of nuclear Mi TF expression in UPS s (89%) and AFX s (80%). Rare UPS s showed non‐specific nuclear HMB 45 or S100 staining. These findings argue against using Mi TF in isolation to differentiate between UPS or AFX and melanoma, and caution in interpreting focal staining for a single additional melanocytic marker. Casein block may eliminate non‐specific staining. Mi TF should be used to support a diagnosis of melanoma only if multiple melanocytic markers are positive.