Immunohistologic patterns of congenital nevocellular nevi

Area of Science:

• Dermatopathology
• Pediatric Dermatology
• Histology

Background:

• Small congenital nevi (SCN) require precise histologic criteria for accurate diagnosis.
• Understanding SCN histology in infants is crucial for differentiating benign lesions from concerning ones.

Purpose of the Study:

• To define sensitive histologic criteria for diagnosing small congenital nevi (SCN) in infants.
• To evaluate the dermal and adnexal involvement of nevomelanocytes in SCN.

Main Methods:

• Examination of 29 SCN biopsy specimens from infants under one year old.
• Utilized serial sectioning and S100 immunoperoxidase staining.
• Follow-up histological analysis in ten patients over a mean of 10.25 years.

Main Results:

• Nevomelanocyte infiltration depth in the dermis was variable; only a minority reached the lower reticular dermis.
• All SCN cases showed focal nevomelanocytic involvement of adnexa (eccrine and pilosebaceous structures) at or below the midreticular dermis.
• Histologic patterns and cytology remained consistent in follow-up specimens, with variable surface area increases observed.

Conclusions:

• Focal adnexal involvement at the midreticular dermis or deeper is a key histologic feature of SCN in infants.
• These findings help establish sensitive diagnostic criteria for SCN, distinguishing them from other pediatric skin lesions.