Pathologic Quiz Case: An 84-Year-Old Woman With a Skin Cyst Containing Ziehl-Neelsen–Positive Structures

The document described a case of an 84-year-old woman with a skin cyst containing Ziehl-Neelsen–positive structures, diagnosed as basal cell carcinoma (BCC) associated with a vellus hair cyst (VHC). The study highlighted that BCC is the most common cutaneous malignant neoplasm, typically occurring in sun-exposed areas of fair-skinned individuals, but rarely associated with cysts. The case presented was unique as it was the first reported instance of BCC arising in association with a VHC. The findings suggested a potential vellus hair origin for BCC, supported by the tumor's connection to the infundibulum of the VHC and its outer root sheath. This association was not previously documented, indicating a novel area for further research into the histogenesis of BCC.