Leptomeningeal carcinomatosis in sinonasal NUT carcinoma: a case report and review of intracranial involvement.

BACKGROUND: Sinonasal NUT carcinoma is a rare and highly aggressive malignancy, frequently diagnosed at advanced stages with poor prognosis. Intracranial spread is uncommon and, to our knowledge, leptomeningeal carcinomatosis has not been previously reported in sinonasal NUT carcinoma. CASE DESCRIPTION: We describe the clinical, radiological, histopathological, and molecular features of a 32-year-old woman with sinonasal NUT carcinoma who developed leptomeningeal carcinomatosis. The patient presented with a rapidly progressive nasoethmoidal mass with intracranial (dural) invasion. Diagnosis was confirmed by nuclear NUT immunoreactivity and identification of a BRD4::NUTM1 fusion. Despite partial response to induction chemotherapy, the disease evolved with neurological deterioration and radiological findings consistent with contiguous intra-axial and diffuse leptomeningeal involvement, leading to death four months after diagnosis. CONCLUSIONS: Sinonasal NUT carcinoma with intracranial and meningeal extension may evolve to leptomeningeal carcinomatosis. Early diagnosis and multimodal treatment, including early surgery, may be crucial to improve prognosis.