A rare case of metastatic solitary fibrous tumor of the pancreas manifesting as a cystic neoplasm: a case report

Abstract

Background: Solitary fibrous tumor (SFT) is a rare mesenchymal tumor that typically arises from the pleura. Although it may appear in other organs, it rarely develops in the pancreas. We report herein a rare case of metastatic SFT of the pancreas originating from an intracranial tumor and subsequently identified as a cystic neoplasm of the pancreas.

Case presentation: A 58-year-old woman with a past medical history of brain tumor visited the hospital for further investigation of a cystic tumor in the pancreas tail. Abdominal imaging showed a heterogeneously enhancing mass that was initially suspected as a neuroendocrine neoplasm, solid pseudopapillary neoplasm, or mucinous cystic neoplasm of the pancreas. Distal pancreatectomy was performed without any intraoperative and postoperative complications. Pathological findings confirmed a diagnosis of malignant SFT of the pancreas with hyperproliferative potential. A histopathological review of her brain tumor revealed that the pancreatic tumor was derived from her brain lesion. The patient developed recurrent brain disease 4 years after the pancreatectomy, but no recurrence has been observed in the abdominal cavity.

Conclusions: SFT should be considered in the differential diagnosis of untypical hypervascular pancreatic mass, particularly in patients with a history of an intrathoracic or intracranial mesenchymal tumor. Immunohistochemical analysis is crucial in detecting this tumor entity. Hyperproliferative status indicates a malignant disease and requires careful postoperative observation.

Keywords: Cystic tumor; Extrathoracic; Hemangiopericytoma; Malignant; Metastasis; Pancreas; Solitary fibrous tumor.

Fig. 1

Endoscopic ultrasonography (EUS) findings. a EUS revealed a well-demarcated cystic mass with solid components in the pancreas tail. b Color Doppler EUS revealed the tumor was hypervascular, particularly on the surface

Fig. 2

Dynamic contrast-enhanced computed tomography (CT) findings. a Plain CT scan demonstrated a 5.5-cm cystic mass with solid components inside in the pancreas tail. b Dynamic CT arterial phase scan demonstrated enhancement in the tumor rim and in the edge of the solid components with non-enhanced interior. c Solid components were gradually enhanced from the outside in the portal phase. d The tumor rim and the solid components had isodensity to the surrounding pancreatic parenchyma in the delayed phase

Fig. 3

Magnetic resonance imaging (MRI) findings. a Solid components were hypointense to the pancreatic parenchyma on T1-weighted imaging. b On T2-weighted imaging, solid components were hyperintense. A large non-enhancing portion on the CT scan showed bright signal intensity, indicating cystic change or necrosis

Fig. 4

Macroscopic and microscopic findings of the resected specimen of the pancreas. a The resected specimen showed a hemispheric mass protruding from the pancreas tail and measuring 5.6 × 5.4 cm in diameter. b Solid components occupied most of this cystic mass. c, d Findings of the H&E staining. Oval and spindle-shaped cells proliferated bluntly with a richly vascular stroma, resembling the structure of hemangiopericytoma. Scale bars, 50 μm. e Immunohistochemical staining was irregularly positive for CD34, a mesenchymal marker. Scale bar, 100 μm. f Nuclear expression of STAT6 was diffusely positive in the immunohistochemical staining. Scale bar, 100 μm

Fig. 5

Histopathological review of the past brain tumor. a, b Findings of the H&E staining. Oval and spindle-shaped cells proliferated similarly with a richly vascular stroma. Scale bars, 50 μm. Immunohistochemical staining (c CD34, d STAT6) showed the same results as that in the pancreatic lesion. Scale bars, 100 μm