Abstract / Summary
Rosai-Dorfman Disease (RDD), also known as sinus histiocytosis with massive lymphadenopathy, is a rare benign non-Langerhans cell histiocytic proliferative disorder that commonly presents with painless cervical lymphadenopathy in young adults. Extranodal involvement occurs in nearly 40% of cases; however, isolated abdominal disease is exceptionally uncommon and may mimic neoplastic lesions radiologically. This case report describes a rare case of mesenteric RDD presenting as an abdominal mass clinically and radiologically suggestive of a Gastrointestinal Stromal Tumour (GIST). A 66-year-old male presented with a 2-week history of abdominal pain and dysuria. Imaging revealed a progressively enhancing soft-tissue mass in the left lumbar region supplied by the superior mesenteric artery, favouring a diagnosis of GIST. Surgical exploration identified a highly vascular mesenteric mass attached to the small bowel. Histopathological examination showed marked lymphoid follicular hyperplasia with sinusoidal proliferation of large histiocytes exhibiting emperipolesis. Immunohistochemistry demonstrated positivity for S100, CD68, and Cyclin D1, while CD15 and CD30 were negative, excluding Hodgkin lymphoma. These findings confirmed the diagnosis of mesenteric RDD. This case highlights the diagnostic challenge posed by isolated abdominal RDD due to its non-specific clinical and radiologic features. Recognition of characteristic histopathological findings and immunophenotypic profile is essential for accurate diagnosis and appropriate management. RDD should be considered in the differential diagnosis of unexplained abdominal masses to avoid misdiagnosis and unnecessary aggressive treatment.