Desmoplastic nested spindle cell tumor of liver: report of four cases of a proposed new entity.

We describe a distinctive tumor of the liver in four children composed of nested spindled and epithelioid cells with extensive desmoplasia that we have termed "desmoplastic nested spindle cell tumor of the liver." All four patients were previously healthy. One patient had a presumptive diagnosis of hepatic hemangioma 11 years prior to presentation. Grossly, the tumors were well circumscribed, lobular white masses, ranging from 2.8 to 15 cm in diameter. These tumors were characterized by the presence of cohesive nests of plump, bland spindle cells arranged in short fascicles with an accompanying desmoplastic stroma. Epithelioid areas ranging from palisading epithelioid cells at the periphery of some nests to pseudoglandular and polygonal cells with intercellular bridges were invariably present. Mitotic activity was low. Calcification and ossification were present. Non-neoplastic bile ducts and hepatic elements were seen both within and surrounding the tumor cell nests. Each tumor displayed cytoplasmic reactivity for vimentin, pan-cytokeratin, CD57, and nuclear staining for WT1. Neuroendocrine markers were negative. Ultrastructurally, the tumor cells showed focally well-developed cell junctions, basal lamina, and few cytoplasmic organelles. All tumors were confined to the liver and were resected without complication. Two patients received postoperative adjuvant therapy for presumed hepatoblastoma. The patients are doing well without recurrence at 7.5 years, 7 years, 5 years, and 8 months post-surgery. The morphologic appearance and immunohistochemical profile of these lesions are unique in our experience and represent a new category of pediatric liver tumor.