Autoimmune acrosyringitis with ductal cysts: reclassification of case of eruptive syringoma.

Syringomas are architecturally complex tumors composed of small, cystically dilated segments of dermal eccrine duct. Syringomas typically form isolated flesh-colored periorbital papules, however, in a peculiar condition termed eruptive syringoma; scores develop simultaneously in near confluence over a large surface area. While traditionally regarded as a neoplasm, more recent observations indicate eruptive syringoma is a reactive proliferation secondary to autoimmune disruption of the acrosyringium. We present the case of a 44-year-old woman with eruptive syringoma of the labia majora and prominent lymphocytic inflammation in the acrosyringium. Immunohistochemical stains confirm that the infiltrate is composed of CD4+ and CD8+ T cells, without significant CD20 B cells or CD138 plasma cells. Sequential sections of the syringoma reveal a complex 3-dimensional architecture with functionally isolated cysts, not connected to adjacent cysts or ducts by a discernable epithelium. These findings support the conclusion that eruptive syringoma is a tortuous proliferation of dermal eccrine ducts and fibrous stroma secondary to autoimmune destruction of the acrosyringium. Conceptually, the disorganized expansion of an eccrine duct syringoma may be analogous to a peripheral nerve traumatic neuroma.