title: Combined melanocytic and sweat gland neoplasm: cell subsets harbor an identical HRAS mutation in phacomatosis pigmentokeratotica.
abstract: Phacomatosis pigmentokeratotica (PPK) is characterized by the co-existence of epidermal nevi and large segmental speckled lentiginous nevi of the papulosa type. PPK, previously explained as 'twin spot' mosaicism due to the postzygotic crossing-over of two homozygous recessive mutations, has recently been shown to derive from one postzygotic activating RAS mutation. Epidermal nevi, including those in PPK, are known to give rise to neoplasms such as trichoblastoma and basal cell carcinoma. Within speckled lentiginous nevi, Spitz nevi and melanoma have been well documented. We report a case of PPK with a combined melanocytic and adnexal neoplasm presenting where the nevi conjoined. Using next-generation sequencing techniques, we were able to identify the same HRAS G13R mutation within both components of the tumor, and to show the absence of additional mutated modifier genes in a panel of 300 cancer-related genes. Given the genetic findings in this rare tumor-type, we suggest that this case may be used as a model for understanding the development of biphenotypic neoplasia or intratumoral heterogeneity in some cases.
authors.affiliation: Department of Medicine, Dermatology Service, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
authors.forename: Janet Y
authors.initials: JY
authors.lastname: Li
authors.forename: Michael F
authors.initials: MF
authors.lastname: Berger
authors.forename: Ashfaq
authors.initials: A
authors.lastname: Marghoob
authors.forename: Umesh K
authors.initials: UK
authors.lastname: Bhanot
authors.forename: Jennifer P
authors.initials: JP
authors.lastname: Toyohara
authors.forename: Melissa P
authors.initials: MP
authors.lastname: Pulitzer
mesh_terms: D000293:Adolescent; D004252:DNA Mutational Analysis; D005260:Female; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D061346:Laser Capture Microdissection; D008545:Melanoma / Q000235:genetics / Q000473:pathology; D009154:Mutation; D018193:Neoplasms, Complex and Mixed / Q000235:genetics* / Q000473:pathology*; D009508:Nevus, Pigmented / Q000235:genetics* / Q000473:pathology*; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology*; D013544:Sweat Gland Neoplasms / Q000235:genetics / Q000473:pathology
chemical_list: C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)
keywords: linear verrucous epidermal nevus; mutation; pigmented nevus