title: Recurrent pigmented macules after q-switched alexandrite laser treatment of congenital melanocytic nevus.
abstract: BACKGROUND
  Q-switch-mode laser treatment of congenital nevi does not result in complete histological clearance, and many patients have partial repigmentation within several months. In addition, the number of recurrent pigmented macules (RPMs) may increase, a major drawback to good cosmetic results. While the mechanism of recurrence is not known.
  
  
  OBJECTIVE
  To help elucidate the mechanism of RPM development, we evaluated the expression of TNF-alpha and E-cadherin on RPM after treatment of congenital nevi with a Q-switched alexandrite laser (QSAL).
  
  
  METHODS
  Thirteen Korean subjects with congenital nevi received QSAL treatment at intervals ranging from 2 to 6 months (mean, 4.5 treatments). Two-millimeter punch biopsy specimens were obtained at their first visit and from RPMs 3-6 months after the last treatment. Expression of E-cadherin and TNF-alpha were determined histochemically in the original nevi and RPM. In addition, one RPM was examined by electron microscopy.
  
  
  RESULTS
  Reduced pigmentation in the treated areas was seen in all cases, but partial repigmentaion was seen as black spots within 6 months after the last QSAL treatment. Compared to the original nevi, the RPMs had increased numbers of melanocytes in the epidermis and reduced nevomelanocytic nests in the dermis. The expression of TNF-alpha and E-cadherin was downregulated in the RPMs compared to the original nevi. Electron microscopy confirmed the increase in melanocytes in the epidermis of RPMs.
  
  
  CONCLUSIONS
  Our findings suggest that the down-regulation of E-cadherin and TNF-alpha may induce the proliferation of melanocytes, resulting in the formation of RPMs.
authors.affiliation: Department of Dermatology and Laboratory of Cell Biology, Institute for Medical Sciences, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Seonghyang
authors.initials: S
authors.lastname: Sohn
authors.forename: Sangeun
authors.initials: S
authors.lastname: Kim
authors.forename: Won Hyoung
authors.initials: WH
authors.lastname: Kang
mesh_terms: D000293:Adolescent; D000328:Adult; D015820:Cadherins / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D004431:Ear, External; D005145:Face; D005260:Female; D006801:Humans; D007866:Leg; D028022:Low-Level Light Therapy; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000378:metabolism* / Q000532:radiotherapy; D009508:Nevus, Pigmented / Q000151:congenital / Q000378:metabolism* / Q000532:radiotherapy; D012878:Skin Neoplasms / Q000151:congenital / Q000378:metabolism* / Q000532:radiotherapy; D013909:Thorax; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D015820:Cadherins; D014409:Tumor Necrosis Factor-alpha