Extranodal Intra-abdominal Histiocytic Sarcoma Initially Diagnosed as Abdominal Tuberculosis.

Histiocytic sarcoma (HS) is a rare and aggressive hematolymphoid neoplasm that frequently presents as extranodal disease. Intra-abdominal involvement is exceedingly rare and may clinically resemble abdominal tuberculosis. We present the case of a 29-year-old woman with abdominal pain, unintentional weight loss of 15 kg (25% of her baseline body weight) over four months, and altered bowel habits. CT demonstrated a large intra-abdominal mass measuring 14 × 11 × 7 cm with internal calcifications and mass effect on adjacent structures. Initial diagnostic evaluation included image-guided fine-needle aspiration followed by diagnostic laparoscopic biopsy, which demonstrated granulomatous inflammation with Ziehl-Neelsen positivity. Given the patient's constitutional symptoms, abdominal imaging findings, granulomatous inflammation with Ziehl-Neelsen positivity on the initial biopsy, and a positive interferon-gamma release assay (IGRA), a presumptive diagnosis of abdominal tuberculosis was established by the multidisciplinary team, and empirical antituberculous therapy was initiated while further diagnostic evaluation continued. Despite treatment, the patient experienced clinical deterioration and radiological progression. Exploratory laparotomy followed by histopathological and immunohistochemical evaluation confirmed extranodal HS. This report illustrates the diagnostic challenge posed by this rare malignancy, particularly when it presents with constitutional symptoms, nonspecific radiological findings, and initial histopathological features suggestive of abdominal tuberculosis. It emphasizes the importance of early tissue diagnosis through comprehensive histopathological evaluation to avoid delays in appropriate oncologic management.