Abstract
Calcifying nested stromal-epithelial tumor (CNSET) is a rare liver neoplasm with unknown histogenesis. The tumor mainly affects children and young adults with a female predominance. Although predominantly indolent, rare tumors with aggressive clinical course have been reported. Here we report a CNSET with unique clinical, microscopic, and molecular features. Clinically, the patient presented with mass-associated liver failure with tumor recurrence 3 years later following liver transplantation. Histologically, the tumor showed a unique watered-silk growth pattern composed of small blue cells and diffuse positivity for CDX2 stain. Genetically, the tumor harbors a novel pathologic mutation in PIK3CA in addition to previously reported CTNNB1 and TERT promoter mutations. The case expands the morphologic and immunohistochemical spectrum of CNSET and suggests potential implication of PIK3CA in targeted therapy.