Melanoma Dissemination Through Bullous Solar Elastosis: Previously Undescribed Pattern of Cancer Dissemination

Metastasis can be classified into three forms based on the route of spread: lymphatic, hematogenous, and seeding within body cavities. We report a case of melanoma exhibiting seeding/dissemination around the primary site through bullous solar elastosis, a previously unreported pattern. A 75-year-old man presented with a black nodule on the right forearm. One year after excision, a bluish-gray macular lesion developed distal to the surgical scar. Histopathology of the primary lesion revealed features of high-CSD melanoma with bullous solar elastosis forming cleft-like spaces in the superficial and mid-dermis, containing scattered melanoma cells. The recurrent lesion demonstrated a widespread band-like distribution of melanoma cells along bullous solar elastosis. This case suggests that cleft-like spaces in bullous solar elastosis may act as conduits for horizontal tumor spread, resulting in clinicopathological features that are distinct from conventional metastasis. Recognition of this pathway may improve diagnostic accuracy and understanding of cancer behavior in chronically sun-exposed skin.