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We report a case of clonal seborrheic keratosis (CPSK) adjacent to Bowen's disease (BD) in a 29‑year‑old male with no history of chronic sun exposure. The lesion presented as a brown, flat papule on the right side of the back. Histopathologically, the CPSK component featured well‑demarcated intraepidermal nests of basaloid keratinocytes, consistent with the Borst‑Jadassohn phenomenon. Adjacent areas showed full‑thickness epidermal atypia, nuclear pleomorphism, and numerous mitotic figures, including atypical forms, characteristic of BD. No clear transitional zone was identified between the two components. These findings align most closely with a collision tumor-coincidental coexistence of two independent neoplasms-rather than true malignant transformation of CPSK into BD. This case underscores the need for careful histologic evaluation to distinguish collision from transformation, particularly in the absence of chronic ultraviolet exposure.