Sarcoidosis with intraabdominal involvement mimicking lymphoma: a diagnostic pitfall of premature closure

Sarcoidosis is a multisystem granulomatous disease with various manifestations. While pulmonary involvement is most common, intra-abdominal sarcoidosis is rare and often mimics malignancy, leading to misdiagnosis and delayed therapy. We describe an elderly woman who was initially misdiagnosed with lymphoma at another center based on imaging demonstrating intra-abdominal lymphadenopathy and ascites and histopathological findings. She was started on corticosteroids in preparation for chemotherapy. Patient developed recurrent ascites requiring repeated paracentesis. However, reevaluation at our institution revealed non-caseating granulomas without malignant cells on omental biopsies. Additional investigations confirmed bilateral hilar and mediastinal lymphadenopathy, and comprehensive microbiological workup excluded infectious causes, including tuberculosis. Following a course of corticosteroid therapy, the patient experienced complete resolution of symptoms and near-complete radiologic improvement on follow-up PET imaging. This case underscores the diagnostic challenges posed by sarcoidosis with atypical intra-abdominal involvement. Careful histological evaluation is critical to avoid misdiagnosis and inappropriate treatment. It illustrates the risk of premature diagnostic closure and anchoring bias, where early attribution of ascites and lymphadenopathy to lymphoma delayed reconsideration despite clinicopathologic discordance, emphasizing the need for diagnostic vigilance to ensure timely and appropriate therapy. • Intraabdominal sarcoidosis can closely mimic malignancy, particularly lymphoma, underscoring the importance of histopathologic confirmation before initiating chemotherapy. • The presence of non-caseating granulomas without atypia or clonality across multiple biopsy sites should raise suspicion for sarcoidosis, even in elderly patients. • Comprehensive exclusion of infectious etiologies, including tuberculosis and fungal infections, is essential prior to establishing a diagnosis of sarcoidosis. • A favorable clinical and radiologic response to corticosteroids supports the diagnosis but should follow, not replace, a tissue-based and multidisciplinary evaluation.