Clinical characteristics of the ALK fusion-positive bladder PMP and efficacy of lorlatinib: a two-case report and literature review.

Pseudosarcomatous myofibroblastic proliferation (PMP) is a rare anaplastic lymphoma kinase (ALK), ALK fusion-associated tumor-like lesion that requires differentiation from inflammatory myofibroblastic tumor (IMT). This article reports two cases of bladder ALK fusion-positive PMP: a 16-year-old male achieved partial remission (PR) postoperatively with lorlatinib but experienced memory decline and mood disturbances, which resolved after dose reduction; a 34-year-old female showed significant tumor shrinkage (PR) without severe adverse reactions. The study confirms the marked efficacy of ALK inhibitors in ALK-positive PMP, but highlights the need to monitor neurotoxicity in adolescent patients. Through analysis of the FN1 (Fibronectin 1)-ALK fusion mechanism and literature review, this study emphasizes the importance of pathological differentiation, individualized treatment, and dynamic cognitive monitoring, providing insights for precision therapy in rare diseases.