Clinicopathologic Features and Outcomes of Actinic Keratosis and Skin Cancer After Hematopoietic Stem Cell Transplantation

ABSTRACT Introduction Patients undergoing hematopoietic stem cell transplantation (HSCT) are at an increased risk of secondary skin neoplasms. However, detailed clinicopathological and therapeutic descriptions are limited. Methods We conducted a prospective, observational, single‐center study including HSCT recipients. Patients with actinic keratosis or skin/mucosal malignancies were evaluated by expert dermatologists, with a histological review. Management followed standard protocols, and patients were stratified according to the National Comprehensive Cancer Network (NCCN) guidelines. Results Of the 2042 HSCT recipients, 96 (4%) developed any actinic keratosis or skin cancer, with a median latency period of approximately three years. The most common lesions were basal cell carcinoma (BCC, 35%), actinic keratosis (30%), and squamous cell carcinoma (SCC, 22%), followed by melanoma (9%). The lesions predominantly appeared on the face and scalp. Almost 20% of invasive SCCs or BCCs exhibited high‐risk histopathological features, most commonly micronodular BCC and deep invasion in SCC. Surgical excision was the primary treatment; however, a high percentage of positive margins was found, especially in SCCs. At follow‐up, 47% of patients developed subsequent lesions, typically of the same histological subtype or actinic keratosis, with a median time to recurrence of 9.5 months. One patient died from metastatic SCC of the lip. Conclusion This study provides the most detailed clinicopathological description of post‐HSCT cutaneous lesions to date. While most tumors were non‐aggressive, the high prevalence of high‐risk features and recurrence highlights the need for dermatological surveillance. Nearly half of patients develop new lesions within months of the first diagnosis, so regular follow‐up is warranted.