Diffuse large B-cell lymphoma presenting as a scalp tumor with skull destruction and neurological symptoms: a case report.

Diffuse large B-cell lymphoma (DLBCL) frequently involves extranodal sites; however, extensive skull destruction and suspected central nervous system (CNS) involvement associated with a scalp lesion are extremely rare. A 70-year-old man presented with a rapidly enlarging scalp tumor. Histopathological examination revealed diffuse proliferation of large atypical B lymphocytes consistent with a non-GCB phenotype of DLBCL. Imaging studies demonstrated a large scalp mass with marked osteolytic skull destruction and extension into the superior sagittal sinus with leptomeningeal enhancement. Systemic evaluation revealed multi-organ involvement, including bone marrow infiltration, leading to a diagnosis of stage IV DLBCL with secondary cutaneous involvement. Immunohistochemical analysis demonstrated expression of receptor activator of nuclear factor-κB ligand (RANKL) in tumor cells. The patient was treated with Pola-R-CHP followed by CNS-directed therapy, including high-dose methotrexate and intrathecal chemotherapy. The tumor showed marked regression, accompanied by improvement of neurological symptoms. This case highlights a rare presentation of DLBCL with skull destruction and suspected CNS involvement. Tumor-associated RANKL expression may be associated with the osteolytic features observed in this case. Early biopsy and systemic evaluation of cutaneous lesions are essential, as they may reflect aggressive systemic disease.