High-Grade B-Cell Lymphoma Presenting as a Giant Intra-Abdominal Mass: Diagnostic Delay and Fatal Outcome in a Young Female

Abstract Background:Intra-abdominal masses in young adults can present significant diagnostic challenges, particularly when radiology and initial histopathology suggest conflicting possibilities. High-grade B-cell lymphoma may mimic GIST or sarcoma both clinically and radiologically, often leading to delayed recognition without comprehensive immunohistochemistry. Case-Presentation: We report the case of a 31-year-old previously healthy woman who presented with a rapidly enlarging abdominal mass associated with early satiety and progressive distension. Cross-sectional imaging repeatedly demonstrated a giant heterogeneously enhancing, predominantly necrotic intra-abdominal mass encasing major mesenteric vessels. The radiological differentials included GIST, peritoneal sarcoma, and lymphoma. Two separate image-guided core biopsies were non-diagnostic or misleading, variably suggesting spindle-cell neoplasm and poorly differentiated malignancy. As the patient’s symptoms worsened, she underwent debulking surgery for symptomatic relief. Postoperative histopathology again revealed an undifferentiated malignant tumor without definitive lineage. Her postoperative course was complicated by chylous ascites—an important but overlooked clue pointing toward lymphatic obstruction from lymphoma. Extended immunohistochemistry ultimately confirmed high-grade B-cell lymphoma; however, the patient deteriorated rapidly and died before chemotherapy could be initiated, likely due to aggressive tumor progression or related complications. Conclusion: Delayed diagnosis due to inadequate sampling and delayed immunohistochemistry can be fatal in intra-abdominal lymphoma. Early multidisciplinary care and timely pathology are critical for high-grade B-cell lymphoma. Keywords: High-grade B-cell lymphoma; Intra-abdominal mass; Necrotic tumor; Diagnostic delay; Chylous ascites; Immunohistochemistry.