Abstract

Hypopigmented blue nevus (HBN) is a rare variant of blue nevus that poses unique diagnostic challenges due to its clinical and histologic overlap with other dermatologic conditions.  In this case study, we describe a 15-year-old female with a well-demarcated, light-brown papule on her right upper chest present since early childhood.  Histological evaluation revealed a proliferation of bland spindle cells within the dermis, surrounded by sclerotic collagen and minimal melanin deposition. The lesional cells were diffusely positive for SOX 10, HMB-45, and p16 and negative for CD34 and Factor XIIIa on immunohistochemical staining, supporting its classification as a hypopigmented blue nevus. While blue nevi are commonly encountered in clinical practice, HBNs are relatively rare and less recognizable due to the lack of melanin pigment in the dermis.  With the presence of bland spindle cells, associated desmoplastic collagen and frequent collagen trapping, other dermatologic entities must be considered, including dermatofibroma, scar, and desmoplastic melanoma.  Accurate diagnosis relies on thorough histological assessment and immunohistochemical analysis. Clinicians and pathologists should remain aware of this variant in order to avoid misdiagnosis due to the absence of expected pigmentation.