Primary mesenchymal tumors of the liver: A practical diagnostic approach

Abstract

Primary mesenchymal tumors represent a rare subset of hepatic lesions with overlapping spindle cell morphology. These lesions pose unique diagnostic challenges for pathologists as they are infrequently seen in general practice and can be easily mistaken for their benign counterparts or mimickers. In the current era of personalized medicine, precise pathologic diagnosis of these lesions is critically important to guide targeted therapy. This expectation is difficult to meet when pathologists face uncommon lesions outside their scope of experience. This challenge is further exacerbated when interpreting small biopsy samples. In this lecture, we first present the clinicopathological features of 6 typical cases: inflammatory pseudotumor, angiomyolipoma, epitheleioid hemagioendothelioma, malignant fibrous histiocytoma, leiomyosarcoma, and follicular dendritic cell sarcoma. On each case, the focus of discussion is on the morphology characteristics and how to differentiate them from metastatic tumors, non-neoplastic lesions and other types of primary spindle cell neoplasms. We then outline a practical diagnostic approach based on the unique features of each entity. This lecture provides a comprehensive guidance to general pathologists and pathology trainees on how to navigate through this group of seemingly complex entities and to arrive at a specific diagnosis.