| Summary: | Nested stromal-epithelial tumor (NSET) of the liver is an extremely rare, newly described, nonhepatocytic, nonbiliary tumor of the liver with less than 40 cases reported in the literature to date [1].This tumor affects predominantly pediatric patients (2–34 years, mean age: 15.2 years, 69% female predominance). Imaging typically discloses a circumscribed heterogenous mass with foci of calcification. NSET has great clinical, radiologic and histologic overlap with many of the entities in its differential diagnoses, including hepatoblastoma, desmoplastic small round cell tumor, synovial sarcoma, teratoma, neuroendocrine tumors, fibrolamellar hepatocellular carcinoma, and metastatic Wilms tumor, among others. Histologically, it is characterized by nests of spindled and epithelioid cells in a desmoplastic stroma often with foci of calcification and/or ossification. The pathogenesis of NSET has yet to be completely elucidated. The majority of reported cases have shown a good prognosis, achieving long term survival after tumor resection with clear margins [2]. However, this tumor can also manifest aggressive behavior as several cases of recurrences and distant metastasis have been documented [3–5]. Recognition of this tumor is critical to avoid misdiagnosis as many higher grade and malignant entities are in its differential diagnosis. We herein present a case of NSET demonstrating immunoreactivity with the neuroendocrine marker synaptophysin, which to our knowledge, has not been previously described. Keywords: NSET, Calcifying nested stromal epithelial tumor, Desmoplastic nested spindle cell tumor, Ossifying malignant mixed epithelial and stromal tumor, Pediatric, Liver
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