Basal Cell Carcinoma and Syringocystoadenoma Papilliferum Arising in Naevus Sebaceous—A Narrative Review

Naevus sebaceous (NS) is a congenital cutaneous hamartoma characterised by epidermal, follicular, sebaceous and apocrine components, with a rare but significant potential for malignant transformation, most commonly into basal cell carcinoma (BCC). Syringocystoadenoma papilliferum (SCAP), a rare adnexal tumour, occasionally arises within NS lesions and may progress to malignancy. This study presents a comprehensive narrative review and a rare case of SCAP arising within NS and subsequently transforming into BCC, highlighting the interplay between these lesions. A systematic review adhering to PRISMA guidelines was conducted using databases including PubMed, OVID Medline and Cochrane, yielding 34 relevant articles after rigorous selection. While NS is present at birth, SCAP can emerge later in life, with hormonal and environmental factors contributing to its development. Both lesions exhibit overlapping genetic alterations, particularly involving PTCH and p16, which are also implicated in the pathogenesis of BCC. This genetic convergence suggests potential mechanisms linking NS and SCAP to malignant transformation, although further research is needed to appreciate their interrelationship fully. This review highlights the need for vigilant monitoring of NS lesions, particularly in the presence of multiple risk factors such as sun exposure and a family history of skin cancer. Early detection and management are critical to mitigate the risk of malignant progression.