Diagnostic Outcomes of Clinically Diagnosed Lichen Planus-Like Keratosis

Lichen planus-like keratosis (LPLK), also known as benign lichenoid keratosis (BLK), are pink/red-brown papules that are thought to represent regressing inflamed solar lentigo or seborrheic keratosis. Prior studies have evaluated the differential diagnosis before biopsy for histologically diagnosed LPLK/BLK; however, diagnostic outcomes and prevalence of malignancy in clinically appearing LPLK/BLK have not been reported. Here, we report a single-institution, retrospective chart review from 2013-2020 evaluating the prevalence of malignancy in a set of lesions clinically appearing as LPLK/BLK. The most common first differential diagnoses were BCC (42%) and LPLK/BLK (35%). The most common histologic diagnosis was BCC (28%), followed by LPLK/BLK (26%). Considering all lesions, 44% were diagnosed as malignant (28% BCC, 14% SCCIS, 1.4% melanoma) and 26% were diagnosed as LPLK/BLK. Conversely, considering lesions with LPLK/BLK first in the differential diagnosis, 33% had a malignant diagnosis (19% BCC, 13% SCCIS, 1% melanoma) and 36% had a diagnosis of LPLK/BLK. These results provide valuable insight into characterizing diagnostic outcomes and malignancy prevalence for clinically appearing LPLK/BLK to guide patient-centered shared decision-making.