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case_images: Abdominal CT scan without contrast (A) revealed a homogenous density retroperitoneal mass(arrows) adjacent to the pancreatic tail. Contrast-enhanced imaging (B, C) showed a similar enhancement pattern to the spleen, suggesting an accessory spleen as a potential differential diagnosis.
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case_images: However, to confirm the diagnosis of accessory spleen and exclude neuroendocrine tumor of the pancreatic tail, a Tc99m-denatured RBC Scan and octreotide scintigraphy are recommended (Fig. 1).
case_images: Octreotide scintigraphy (left side) and denaturated RBC scan (right side) revealed no uptake, excluding neuroendocrine tumor of the pancreatic tail and accessory spleen.
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case_images: This finding suggested that the lesion did not originate from the spleen or represent a neuroendocrine tumor (Fig. 2).
case_images: Abdominal MRI with IV contrast demonstrated heterogeneous typical enhancement of the spleen in T1-weighted axial contrast-enhanced early arterial phase images (A), with similar enhancement observed in the retroperitoneal mass(arrow). Late arterial and portal phases also showed enhancement of the lesion comparable to the spleen (B, C). The lesion appeared as a hypersignal mass in T2-weighted images (arrow) (D). In the ADC (Apparent diffusion coefficient) map and DWI (Diffusion-weighted imaging) sequences (E, F), the lesion showed a high diffusion signal similar to the spleen.
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case_images: IV contrast was performed to further evaluation (Fig. 3). In MRI images the lesion exhibits features similar to the spleen.
case_images: Histologic section of the retroperitoneal mass. (A) Germinal centers traversed by sclerotic penetrating vessels and hyalinization-lollipop follicles (arrow). (B) Mantle zones are thickened with lymphocytes arranged in layers - onion skin appearance. (C) The inked abdominal mass margin is obvious (*) with muscle fibers and vessels beneath it. Follicle with features of Castleman disease (arrow).
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case_images: The mass was completely excised, and the postoperative pathological examination revealed features consistent with Castleman disease (hyaline-vascular type) (Fig. 4).