Abstract
Hepatic marginal zone B-cell lymphoma (MZL) is a rare and challenging entity that is often misinterpreted as hepatocellular carcinoma owing to its non-specific radiological features. The current case report details the clinical presentation, diagnosis and treatment of an older adult female with hepatic MZL involving both lobes, complicated by Sjögren's syndrome and common variable immunodeficiency. Given the patient's immunodeficiency and the risks associated with chemotherapy, involved site radiotherapy (ISRT) was administered as the primary treatment. Using a response-adapted approach, an initial radiotherapy dose of 24 Gy over 16 fractions was delivered to the major hepatic lesion, followed by a local boost to both lobes after significant tumor shrinkage. The patient tolerated the treatment well with minimal side effects, and post-treatment imaging showed a complete metabolic response. This case highlights the effectiveness of response-adapted ISRT in managing hepatic MZL in immunocompromised patients and underscores the need for individualized treatment approaches for rare lymphomas.