The role of immunosuppression in squamous cell carcinomas arising in seborrheic keratosis

Background: Seborrheic keratoses (SK) are common skin neoplasms considered to be benign. Reports of associated squamous cell carcinoma arising within seborrheic keratosis (SCC-SK) have been described. Objective: To describe the histopathologic characteristics of SCC-SK and identify predisposing factors in formation of these rare lesions. Methods: There were 162 cases of SCC-SK in a span of a decade (2003-2014). All of the histopathologic specimens and medical records were reviewed. Data from these patients were compared to a control group with seborrheic keratosis who were matched by age, sex, and location of lesion from the same time period (n = 162). Results: SCC-SK has the classic histopathologic features of SK, such as hyperkeratosis, parakeratosis, papillomatosis, and pseudohorn cysts. The areas of squamous cell carcinoma were characterized by areas of squamous dysplasia (100%), hypogranulosis (79.6%), squamous eddies (79.6%), solar elastosis (80.9%), and brown pigmentation (59.9%). Patients with a history of immunosuppression had an increased risk for developing SCC-SK (19% vs 3%; P < .01), particularly when inhibition was transplant-associated (10% vs 0%; P < .01). Limitations: This was a single center, retrospective study. Conclusion: SCC-SK occurs more often in elderly men with a history of immunosuppression associated with organ transplants.