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TOPLINE:

In a French study, anogenital basal cell carcinomas (BCCs), a rare subtype occurring in sun-protected areas, most often affected the vulva in women, with some arising on lichen sclerosus. Recurrence occurred in 15% of cases, and genomic analysis showed low mutation burden, no ultraviolet (UV) signatures, and frequent PTCH1 mutations.

METHODOLOGY:

• The retrospective-prospective cohort study included 50 patients (average age at diagnosis, 78 years; 40 women) with anogenital BCCs diagnosed between 2006 and 2024
• Researchers examined clinical features of all tumors and performed genomic analysis of 12 tumoral and 12 matched nontumoral tissues.
• The average tumor size was 4.1 cm. Treatment included surgical removal alone in 42 patients (84%) and neoadjuvant hedgehog inhibitors in three patients (6%).
• Other outcomes assessed were local recurrence, defined as a new tumor arising within the BCC scar, and human papillomavirus (HPV) test results.

TAKEAWAY:

• The vulva (34 cases) was the most common site in women, and the perianal region was the most common site in men (five cases). Of the vulvar BCCs, 18% developed on histologically confirmed lichen sclerosus. HPV testing was negative in cases with positive p16 staining.
• Overall, three patients with a prior history of cancer had previously received radiation in the area where the BCC developed. Tumors were most often nodular (46%) or infiltrative (45%) subtypes.
• Of the 48 treated patients, local recurrence occurred in 15% over a median follow-up period of 7 years.
• Genomic analyses (n = 12) demonstrated a low tumor mutational burden, infrequent TP53 mutations (two cases), frequent PTCH1 mutations (nine cases), “confirming their exquisite dependence on sonic hedgehog (SHH) pathway activation,” and no UV-induced mutational signatures.

IN PRACTICE:

Anogenital BCCs are “rare, can be associated with lichen sclerosus, lack detectable HPV involvement, and exhibit a higher recurrence rate than UV-induced BCC,” the authors wrote. 

“While anogenital BCCs are SHH-dependent and share several genetic features with sun-exposed BCCs,” they added, “they also display key differences, including a lower mutation burden, absence of UV mutational signatures, and a reduced frequency of TP53 mutations.” 

SOURCE:

The study was led by Lea Dousset, MD, PhD, Dermatology Department, Saint André Hospital, Bordeaux University Hospital, Bordeaux, France, and was published online on August 23 in the Journal of the American Academy of Dermatology.

LIMITATIONS:

Limitations included a small sample size, retrospective component of the study design, absence of patients treated with Mohs micrographic surgery, and the absence of a matched control group. Moreover, HPV testing was not performed for all cases.

DISCLOSURES:

The study was supported by grants from INSERM, INCa, and the ARC Foundation. The authors declared having no competing interests.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.