Retroperitoneal Solid Pseudopapillary Tumor Mimicking Adrenal Malignant Tumor in a 67-Year-Old Man

Solid pseudopapillary tumor (SPT) is a low-grade malignant tumor of the pancreas. SPT typically affects women and can occur in ectopic pancreatic region; however, it also occurs rarely in retroperitoneum. The tumor may be bulky at the time of diagnosis since there is no specific clinical manifestation. Here we present an older male case with retroperitoneal SPT. A 67-year-old man consulted for intermittent fever and lumbago. His basal hormonal profile screened out a functional tumor. Computed tomography (CT) showed a gigantic mass in his left adrenal region. A normal left adrenal gland was not identified, and the tumor's feeding artery was recognized as the left adrenal artery by the contrast-enhanced CT. Adrenal malignant tumor was suspected, and tumor resection was performed. The resected tumor size was 15 × 10 × 9 cm. Histologically, epithelial-like cells with round nuclei and a small amount of eosinophilic cytoplasm proliferated in papillary (around the blood vessels) or uniformly solid form. By immunostaining, tumor cells were vimentin, CD56, cytokeratin AE1/AE3, CD10, β-catenin in the nucleus, cyclin D1, and PgR positive. These findings led to the diagnosis of SPT. Although rare, SPT should be considered as a differential diagnosis in cases of a mass arising from the adrenal region.