EP657 - Treatment, Recurrence, and Staging in Anogenital Squamous Cell Carcinoma (agSCC) Vary by Specialty: A Retrospective Cohort Study

Purpose/Background: Anogenital squamous cell carcinoma (agSCC), including perianal, vulvar, penile, scrotal and perineal SCC, is a rare malignancy treated by multiple specialties. While histopathology is often similar, six distinct staging systems exist for agSCC, with different criteria for perianal, vulvar, penile, and perineal/buttock skin SCC. Treatment varies by specialty, including wide local excision (WLE) mostly used by colorectal surgeons, Mohs micrographic surgery (MMS) used by dermatologists, or chemoradiotherapy (CRT). Comparative data across specialties are limited, especially regarding intervention types and recurrence which highlights the need for interdisciplinary collaboration and standardized approaches.

Our objectives are to identify factors influencing treatment selection and recurrence, and to compare staging systems used for agSCC.

Methods/Interventions: We conducted a retrospective cohort study of agSCC cases treated at a tertiary academic center between 2017-2025. Adults (≥18 years) with histologically confirmed early-stage agSCC were included. Those with invasion beyond the skin, nodal involvement, or metastasis at presentation were excluded. We extracted data from health records, including demographics, tumor location, treatment, and recurrence. Staging was compared using the following systems: AJCC anal/perianal SCC, AJCC penile SCC, AJCC vulvar SCC, FIGO vulvar SCC, AJCC skin SCC, and BWH skin SCC.

Results/Outcomes: Fifteen patients were included (mean age 65.1 [SD 12.1]; 6 [40.0%] males). The median BMI was 25.2 (range 19.4-45.9). At initial presentation, six patients had only perianal lesions (6,40%), two had vulvar (13.33%), four had penile (26.7%) while one had both vulvar and perineal (6.7%), and one had both perianal and perineal (6.7%). Ten patients (67%) had carcinoma in situ (SCCIS), and five (33%) had invasive SCC. Among the ten SCCIS cases, three (30%) underwent MMS-all with penile tumors. There were two recurrences (20%)-one after WLE (perianal) and one after MMS (penile). Among the five invasive SCC cases, four (80%) were treated with WLE and one with CRT; two recurrences (40%) followed WLE (perianal and perineal). For SCCIS, staging was generally consistent across systems, except for one perianal case upgraded to T2a due to a larger size (4.5 × 3.5 cm). For invasive SCC, staging varied widely as shown in the Table.

Conclusion/Discussion: This analysis reveals variation in agSCC treatment across specialties, especially for SCCIS, where both WLE and MMS were used-though the MMS approach was primarily applied to penile SCCIS. Recurrence appeared more frequently after WLE, though a larger sample size is needed for a definitive conclusion. For invasive SCC, staging systems varied considerably; for instance, case number 3 (Table) with perianal SCC was staged from I to IIIA depending on size criteria in different systems. Standardized treatment algorithms and multidisciplinary collaboration are essential. A larger cohort and longer follow-up are needed to better evaluate treatment, recurrence, and staging for agSCC.

Table 1. Invasive SCC cases staging variations
Comparison of staging classifications for invasive anogenital SCC cases across six established systems, demonstrating variation in stage assignment by tumor site and criteria.