Retrospective Cohort: Genomic Differences Between Pigmented Spindle Cell Nevi of Reed and Reed-Like Melanomas

Lauren S. Mohan, Ayesha U. Khan, Bin Zhang, Victor L. Quan, Katherine Shi, Elnaz Panah, Maria Cristina Isales, Pedram Yazdan, Yongzhan Zhang, Nike Tsiapera Beaubier, Timothy J. Taxter, Elsy V. Compres, Daniel Kim, Kevin P. White, Pedram Gerami

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

BACKGROUND: Some melanomas closely resemble pigmented spindle cell nevi (PSCN) of Reed histologically. The distinction of these entities is important for clinical management. A recent study showed most PSCN (78%) are fusion-driven, commonly involving NTRK3 (57%). Conversely, BRAF V600E mutations are not characteristic of PSCN but are frequent in melanoma. OBJECTIVE: In this study, we assessed clinical, histologic and genomic differences between PSCN of Reed and Reed-like melanomas (RLMs). METHODS: We performed BRAF V600E immunohistochemistry (IHC) for 18 PSCN and 20 RLM cases. All 23 benign PSCN cases previously underwent whole transcriptome and targeted DNA sequencing with a 1711 gene panel. RESULTS: We previously demonstrated the majority of PSCN (18 of 23) has chimeric fusions. Among PSCN without a chimeric fusion, BRAF mutations were common. Noncanonical BRAF mutations were identified in 2 of 5 nonfusion cases, and 1 case had a canonical BRAF mutation. Alternatively, 70% of RLM demonstrated a BRAF V600E mutation. RLM also occurred more frequently in older patients. LIMITATIONS: The overall sample size was small. CONCLUSIONS: In diagnostically challenging cases, ancillary IHC studies can assist in distinguishing PSCN from RLM. Our study suggests positive staining by IHC for BRAF V600E and older age strongly favors a diagnosis of RLM.

Original languageEnglish (US)
Pages (from-to)641-647
Number of pages7
JournalThe American Journal of dermatopathology
Volume42
Issue number9
DOIs
StatePublished - Sep 1 2020

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Dermatology

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