Presence of background actinic keratosis reported in surgical margins of solid organ transplant recipients during Mohs micrographic surgery

Summary: Skin cancer is a significant cause of morbidity and mortality among solid organ transplant recipients (SOTR). SOTR have nearly a 200x greater risk of developing SCC due to immunosuppression and accounts for nearly 5% of mortality compared to an immunocompetent population. Thus, many SOTR require Mohs micrographic surgery (MMS) for skin cancer treatment. A challenge during MMS for SOTR is the presence of background actinic keratoses (BAK) at surgical margins that may resemble squamous cell carcinoma in situ (SCCis). We hypothesize that SOTR are more likely to have BAKs observed during MMS, larger tumor sizes, and require more surgical stages than non-SOTR. We performed a retrospective chart review of all patients who underwent MMS from August 1, 2022, to January 31, 2023, at the University of Pittsburgh Medical Center. 458 patients underwent MMS: 96 were SOTR and 362 were non SOTR. There was no significant difference in the incidence of BAKs reported during MMS between SOTR and non-SOTR (20.3% vs. 79.6%, p<0.136). However, SOTR with BAKs had larger tumor sizes (1.5 vs. 1.1 cm, p<0.05), required more surgical stages (2.125 vs 1.67, p<0.01), and received MMS at younger ages (67.5 vs. 72.9, p<0.05). Furthermore, SOTR with BAKs were more likely to have a history of previous field therapy usage for prior AKs than non SOTR (83.3% vs. 71.3%, p<0.001) as well as have a history of smoking than non-SOTR (75% vs 43.6% p<0.005). This may suggest that SOTR patients may have greater baseline photodamage than non-SOTR as well as greater risk factors for development of BAK such as smoking. While there was no difference in incidence of BAK amongst SOTR and non-SOTR, our findings may indicate that BAK may make interpretation of the tissue more difficult for the surgeon.