Primary hepatic diffuse large B-cell lymphoma in a patient with polycystic liver disease: a case report and literature review.

Primary hepatic lymphoma (PHL) is an extremely rare extranodal non-Hodgkin lymphoma confined to the liver, accounting for <0.016% of all non-Hodgkin lymphomas. Polycystic liver disease (PLD) is a benign genetic disorder characterized by multiple hepatic cysts. The coexistence of PHL in a patient with PLD has not been previously reported. A 68-year-old woman with a long-standing history of polycystic liver and kidney disease presented with progressive abdominal distension. Laboratory tests showed markedly elevated lactate dehydrogenase (947 IU/L) and soluble interleukin-2 receptor (599 U/mL), with normal tumor markers. Contrast-enhanced CT identified a mass in the right hepatic lobe, and 18F-FDG PET/CT revealed a large hypermetabolic lesion (SUVmax 22.5) without extrahepatic involvement. Contrast-enhanced ultrasound (CEUS) using Sonazoid demonstrated peripheral rim-like hyperenhancement in the arterial phase, rapid wash-out at 50 seconds, and absent enhancement in the Kupffer phase at 10 minutes post-injection, findings that guided targeted biopsy. Ultrasound-guided liver biopsy confirmed diffuse large B-cell lymphoma (DLBCL), non-germinal center B-cell (non-GCB) subtype, with immunohistochemistry showing CD20+, CD79a+, Bcl-6+, MUM1+, Bcl-2+ (80%), c-Myc+ (20%), Ki-67 (85%), and EBER negative. Bone marrow biopsy showed no involvement. The patient was treated with six cycles of R-CHOP chemotherapy. One year after treatment completion, restaging confirmed complete remission with no evidence of disease recurrence. To our knowledge, this is the first reported case of primary hepatic DLBCL occurring in a patient with polycystic liver disease. The diagnostic challenges posed by the polycystic background highlight the potential value of multimodal imaging, particularly contrast-enhanced ultrasound with Sonazoid, in characterizing lesions in this setting. While longer follow-up is needed, this case suggests that PHL should be considered in the differential diagnosis of new solid liver lesions in PLD patients, and that standard immunochemotherapy may achieve complete remission even in patients with underlying liver disease. Histopathological confirmation remains essential for diagnosis.