Prevalence of ALK gene alterations among the spectrum of plexiform spitzoid lesions

Deborah Saraggi, Roberto Salmaso, Carolina Zamuner, Giada Munari, Cristiano Lanza, Mauro Salvatore Alaibac, Franco Bassetto, Massimo Rugge, Maria Cristina Montesco, Lorenzo Cerroni, Matteo Fassan

Research output: Contribution to journalArticlepeer-review


Background: ALK receptor tyrosine kinase gene (ALK) rearrangements have been described in spitzoid lesions with a plexiform growth pattern. Objective: To investigate the prevalence of ALK alterations in a large series of spitzoid lesions. Methods: ALK immunohistochemical and fluorescence in situ hybridization analyses of 78 spitzoid plexiform lesions including 41 Spitz nevi, 29 atypical Spitz tumors (ASTs), and 8 spitzoid melanomas. Results: ALK immunohistochemical staining was observed in 14.6% of Spitz nevi (6 of 41) and 13.8% of ASTs (4 of 29); the spitzoid melanomas were ALK negative. Fluorescence in situ hybridization confirmed ALK translocation in 9 cases and amplification in 1 case. In 2 of the translocated cases it was possible to determine the fusion partner gene (ie, tropomyosin 3 gene [TPM3] or dynactin 1 gene [DCTN1]). Of the 4 cases of AST examined, 2 carried the B-Raf proto-oncogene, serine/threonine kinase gene (BRAF) V600E mutation. The 10 patients had a mean age of 18.7 years (range, 1-39) and a female predominance (female-to-male ratio, 7:3). Seven lesions arose on the extremities; the 2 lesions occurring in infants were located on the face. The lesions’ mean diameter was 6.2 mm (range, 3-13), and their mean Breslow thickness was 1.83 mm (range, 0.6-3.6). The results of sentinel node biopsy were negative in 2 ASTs. Limitations: BRAF status was tested in only 4 of 10 samples because of the limited amount of material. Conclusion: ALK alterations characterize a significant subset of spitzoid lesions.

Original languageEnglish
Pages (from-to)728-735
Number of pages8
JournalJournal of the American Academy of Dermatology
Issue number4
Publication statusPublished - Oct 1 2018


  • ALK
  • atypical Spitz tumor
  • plexiform melanocytic lesions

ASJC Scopus subject areas

  • Dermatology


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