Nested stromal epithelial tumor of the liver: six cases of a distinctive pediatric neoplasm with frequent calcifications and association with cushing syndrome.

Rare cases of nonhepatocytic mixed stromal and epithelial tumors of the liver with associated calcification and ossification have been described previously. We report 6 similar cases in children, including 2 cases associated with ectopic ACTH production. The patients were between 2 and 14 years of age at diagnosis. All tumors presented as a solitary liver mass with no extrahepatic involvement. Two adolescent females with palpable abdominal tumors presented with Cushing syndrome that abated after excision of the tumors. The other children had tumors identified incidentally on imaging studies or at laparotomy. All tumors were well circumscribed, ranging in size from 4.0 to 30.0 cm in greatest diameter. Histologically, they shared an organoid arrangement of cellular nests that were comprised of an admixture of both spindled and epithelioid cells. These cellular nests were surrounded by a band of delicate myofibroblasts and set in a dense fibrous stroma that contained slit-like to dilated blood vessels. A variable proliferation of bile ducts extended from the fibrous stroma and focally surrounded the cellular nests. One case showed a sheet-like overgrowth of the nested cells with associated necrosis. The cellular nest cells were immunoreactive for EMA, CD56, neuron specific enolase, pan-cytokeratin (4 of 6 cases), vimentin (5 of 6 cases), and WT-1 amino terminus (4 of 6 cases). Cytokeratin and EMA stained mostly epithelioid nest cells, with vimentin and WT-1 staining predominantly the spindled nest cells. The 3 cases from adolescent females showed immunoreactivity for ACTH in the nested cell population but not in the surrounding stromal cells. Immunohistochemical stains for synaptophysin and chromogranin were negative in all cases. Psammomatous calcifications were present focally in 2 cases and were extensive in 3 cases. Ossification or osteoid formation was present in 4 cases. The 1 patient whose tumor had sheet-like overgrowth of the nested cell population had a local recurrence with multiple hepatic nodules 1 year following the original resection. A 2-year-old patient has been subsequently diagnosed with nephroblastomatosis and Wilms tumor of the kidney. Follow-up information was available in an additional 3 patients with no tumor recurrence or metastatic disease at 2, 3, and 14 years.