Diffuse Large B-Cell Lymphoma Presenting With Isolated Splenomegaly in a 42-Year-Old Female: A Rare Incidence of Primary Splenic Involvement.

Primary splenic involvement by diffuse large B-cell lymphoma (DLBCL) is uncommon and may present with nonspecific clinical features, making diagnosis challenging. We report the case of a 42-year-old female who presented with gradually increasing abdominal distension and weight loss over three months, without fever, night sweats, or lymphadenopathy. Examination revealed massive splenomegaly, while routine laboratory tests were unremarkable. Ultrasound and CT imaging demonstrated isolated splenomegaly, and PET-CT showed increased metabolic activity confined to the spleen. Bone marrow biopsy did not reveal any diagnostic abnormalities. The patient underwent diagnostic splenectomy, and histopathology confirmed DLBCL of the non-germinal center B-cell subtype. Immunohistochemistry was positive for CD45, CD20, BCL2, and MUM1, with a Ki-67 index of 60%. She received six cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy, which she tolerated well. Post-treatment PET-CT revealed a complete metabolic response, and subsequent follow-up has shown no evidence of disease recurrence. This report illustrates that isolated splenomegaly can be the first and only manifestation of DLBCL and emphasizes the role of splenectomy as both a diagnostic and therapeutic option in carefully selected patients.