Managing keratoacanthoma: Watchful waiting as an option

Summary: Abstract Body: Keratoacanthoma (KA) is a rapidly growing tumor that often regresses spontaneously. Some classify KA as a variant of squamous cell carcinoma and thus surgical excision is often used as first-line treatment. Our aim was to assess the frequency of spontaneous KA regression. A retrospective chart review was conducted at the San Francisco VA Hospital, of veterans with pathology confirmed KA, 2014-2024. This cohort consisted of 328 patients (39–97y, median 75y IQR=13, 320 male/8 female). In 45 cases the pathology showed complete excision during initial shave biopsy. Among the remaining 283 cases, spontaneous resolution occurred in 216 patients (76%) while in 67 (24%), persistent tumor was seen on pathology after excision. Thus, watchful waiting could be a consideration in the majority of patients. The 328 patients were monitored over 961±864 days, with 5.9±5.9 follow-ups. Recurrences were uncommon (3/328 lesions), with no metastases seen. Of lesions that received surgery (164/283), 2 recurred and of those that spontaneously resolved 1 recurred (1/119). Thus, surgery did not decrease the incidence of recurrence in this cohort (1.2% vs. 0.8%, respectively). Notably, 97/283 (45%) underwent a potentially unnecessary excision (pathology showed scar). Watchful waiting, rather than surgical referral could help avoid the inconvenience, potential morbidity, and cost associated with surgery. KA is a lesion that requires attention, due to its rare potential to exhibit malignant behavior. This review suggests that patients could be offered observation to determine lack of spontaneous regression, before referral for surgery. Surprisingly, surgery did not improve the frequency of recurrence in this cohort. Along with the high incidence of spontaneous regression and lack of metastases observed, these findings suggest that patients can safely be offered watchful waiting as a viable alternative to surgery. Giselle Vitcov³, Brook H. Abegaze^{1, 2}, Madel Bridgewater², Ruby Ghadially^{1, 2} 1. Dermatology, University of California San Francisco, San Francisco, CA, United States. 2. Dermatology, San Francisco VA Health Care System, San Francisco, CA, United States. 3. Dermatology, The University of Arizona College of Medicine Phoenix, Phoenix, AZ, United States. Clinical Research: Epidemiology and Observational Research