Trophogram, an immunohistochemistry-based algorithmic approach, in the differential diagnosis of trophoblastic tumors and tumorlike lesions.

Recent histopathologic and molecular studies of trophoblastic cells in the normal placenta and in a variety of trophoblastic diseases have revealed that the latter recapitulate the differentiation of normal trophoblast in the early developing placenta. This new knowledge, especially the identification and characterization of the protein markers expressed in human trophoblast, not only helps elucidate the pathogenesis of trophoblastic lesions but also provides a repertoire of immunohistochemical markers that may facilitate the diagnosis of various trophoblastic diseases. This article reviews the recent advances in the trophoblast-associated markers that have been reported to be useful in the differential diagnosis of trophoblastic tumors and tumorlike lesions. Moreover, a "trophogram," which is a stepwise and rational immunohistochemistry-based approach, will be introduced. The trophogram may prove to be useful in assisting the differential diagnosis of various trophoblastic diseases in diagnostic pathology.