Microbiological and clinical outcomes of single-stage minimal excision of inflamed epidermal cysts without routine antibiotic treatments: A dual-center retrospective cohort study.

Inflamed epidermal cysts have traditionally been managed using a 2-stage approach based on the assumption that inflammation indicates active infection. However, emerging evidence suggests that sterile inflammation resulting from keratin-induced foreign body reactions may be more common than actual infections. This study aimed to evaluate the microbiological profiles and clinical outcomes of immediate excision and primary closure of inflamed and non-inflamed epidermal cysts without the use of routine antibiotic therapy. This retrospective cohort study was conducted using prospectively collected clinical data between May 2023 and May 2025. Adult patients with clinically suspected epidermal cysts underwent immediate surgical excision and primary closure regardless of inflammation status. Intraoperative bacterial cultures were performed, and antibiotics were administered only when clinically indicated. Among 444 histologically confirmed cases of epidermal cysts, 254 (62.4%) were classified as inflamed. Positive bacterial cultures were more common in the inflamed cyst group than in the non-inflamed cyst group (P = .003); however, most isolates were skin commensals. Staphylococcus aureus was isolated from 26 cases (24 inflamed and 2 non-inflamed), with methicillin-resistant S aureus detected in 13 of the 24 inflamed cases. The overall complication rate was 2.5%, with no significant difference between the groups (3.1% vs 1.3%, P = .332). Only 1 immunosuppressed patient harboring methicillin-resistant S aureus required reoperation. Immediate surgical excision with primary closure is a safe and effective treatment for both inflamed and non-inflamed epidermal cysts. Routine antibiotic therapy and delayed surgery may not be necessary in most cases, supporting a simplified, single-stage management approach.