Category: Abdominal Imaging, Region: Abdomen-Pancreas, Plane: Axial
ABSTRACT Most cases of pancreatoblastoma, a rare malignant epithelial tumor of the pancreas, are seen in the pediatric population. The rarity of pancreatoblastoma, the similar radiologic findings to those seen in other pancreatic lesions, and its histopathologic heterogeneity, make its preoperative diagnosis in adults a real challenge. We report the ultrasound, computed tomography and magnetic resonance imaging correlative findings of a histologically proven pancreatoblastoma in a 37-year-old puerperal woman. Pancreatoblastoma should be considered in the differential diagnosis of a pancreatic mass presenting atypical imaging features. CASE REPORT A 37-years-old female who had a dystocic labour with severe blood loss requiring transfusion, presented to emergency department 2 weeks later complaining of fatigue and prostration. Physical examination revealed a tender epigastric lump. Laboratory results were unremarkable except for severe anemia (hemoglobin 5,4 g/dl). Abdominal ultrasound (US) performed in order to clarify the origin of the lump detected at physical examination, revealed a huge epigastric mass, heterogeneous and predominantly hypoechoic with cystic cavities (fig. 1a). At Doppler-US there was intense arterial and venous flow (fig. 1b). Abdomino-pelvic computed tomography (CT) showed a large, lobulated abdominal mass, with partially ill-defined margins, and heterogeneity due to the presence of cystic and solid areas (fig. 2a). Solid areas were highly vascularized (fig. 2b). It was completely independent from the uterus and ovaries, which have the normal postpartum appearance. The mass pushed away the neighborhood structures, receiving feeding vessels from them, making difficult the identification of the starting point; the duodenal arch was anteriorly deviated, suggesting a retroperitoneal origin (fig. 2c, 2d). The pancreatic contour blended with the mass. The portal vein showed cavernomatous transformation, the celiac axis and the superior mesenteric artery were surrounded by tumor (fig. 3), and there was distal pancreatic ductal dilatation (fig. 2b). Magnetic resonance imaging (MR) was performed to improve the characterization of the lesion, and revealed focal areas of high signal intensity on T1-weigthed images consistent with intratumoral hemorrhage (fig. 4a, 4b) and solid component revealed intense enhancement (fig. 4c, 4d). On T2-weigthed images the mass was heterogeneous hyperintense with hypointense solid components (fig. 5). Neither adenopathy nor metastases to other organs were found. A preoperative diagnosis of a solid-pseudopapillary neoplasm of the pancreas was suggested based on the patient´s age and gender, and on the imaging findings. The initial percutaneous true-core biopsy of the lesion was thought compatible with solid-pseudopapillary neoplasm of the pancreas. The patient was sent to another institution more experienced with these lesions, to confirm (un)resectability and to perform a wedge surgical biopsy. Surgical exploration of the pancreatic mass revealed a huge tumor with gastric and transverse colon invasion, and also portal vein invasion with secondary portal hypertension, without arterial invasion. A portal-caval shunt was done. At the surgical biopsy, the diagnostic features of pancreatoblastoma were recognized. Microscopy showed abundant small tumor cells that exhibited an organoid growth pattern with focal acinar features, separated by cellular stroma. In a few foci, the tumor cells had a very epithelioid appearance with clusters of squamoid cells and occasional keratinization (fig. 10). Immunohistochemical staining showed a positive reaction for epithelial markers cytokeratin AE1/AE3, CAM53, CK903, CK7 and focally the neuroendocrine marker chromogranin A (fig. 11). Tumor cells stained negative for CK20, vimentin, CD10, RP and nuclear β-catenin. The Ki-67 (MIB-1) labeling index was > 60% (fig. 11). The morphologic and immunophenotypic features, together with evidence of mixed acinar differentiation and squamoid corpuscles, supported the diagnosis of pancreatoblastoma. After surgery, the patient was referred to the oncology department for palliative chemotherapy. She died one year after the initial presentation.