High-Grade B-Cell Non-Hodgkin Lymphoma of the Cranial Vault Presenting with Scalp Swelling and Neurological Deficits in an Elderly Immunocompetent Female: A Case Report

Primary non-Hodgkin lymphoma (NHL) of the cranial vault is an exceedingly rare extranodal presentation of lymphoma, often posing significant diagnostic challenges due to its variable clinical and imaging characteristics that can mimic more common cranial masses. We present the case of a 72-year-old previously healthy and immunocompetent woman who developed a progressively enlarging, firm, nontender scalp swelling over the right parieto-occipital region since March 2024. Starting November 2024, she experienced new-onset associated symptoms including left-sided weakness, persistent dull aching headache, and mild drowsiness. Despite initial differential diagnoses that included mesenchymal tumors, plasmacytoma, metastatic carcinoma, and meningioma, surgical biopsy and subsequent detailed histopathological examination with immunohistochemistry confirmed a diagnosis of high-grade B-cell NHL. Whole-body positron emission tomography-computed tomography and/or bone marrow biopsy could not be performed due to resource constraints; therefore, the absence of systemic disease could not be definitively confirmed and this is acknowledged as a limitation when classifying the lesion as “primary” cranial vault lymphoma. This case highlights the unusual cranial vault presentation of this aggressive malignancy in an immunocompetent patient, the importance of a broad differential diagnosis for calvarial/cranial vault lesions, and the necessity of histopathological confirmation for accurate diagnosis and appropriate management. Given the high-grade histology and the relatively short available follow-up, longer-term surveillance is required to better characterize treatment response and prognosis.