Lipoblast: morphologic features and diagnostic value

Lipoblasts are conceptually a precursor or immature form of adipocytes and histologically defined as lipid-containing, mono－ or multivacuolated cells possessing hyperchromatic, indented or often scalloped nuclei. They are essentially identified in neoplastic conditions and assumed to recapitulate, to some extent, the differentiation process of normal fat (adipogenesis) like their potential normal counterpart, preadipocyte or preadipose cell. Traditionally, great emphasis has been placed on the identification of lipoblasts in diagnostic pathology, particularly of liposarcoma. However, it is not always an easy task for pathologists because of a variety of histological mimics such as Lochkern cells, brown fat cells and pseudolipoblasts. Currently, lipoblasts are not a prerequisite for the diagnosis of liposarcoma partly because of some benign tumors harboring lipoblasts or lipoblast-like cells such as spindle cell/pleomorphic lipoma and chondroid lipoma, although their presence is still crucial for proper diagnosis. This review summarizes the clinicopathologic features of lipoblasts, their histological mimics and representative benign tumors carrying lipoblasts to facilitate routine pathology practice and to avoid erroneous diagnosis of liposarcoma.