The nature of atypical multinucleated stromal cells: a study of 37 cases from different sites.

The morphology, immunophenotype and ultrastructure of atypical multinucleated stromal cells in 37 specimens from different anatomical sites were compared. Overall, cellular morphology was similar between sites but nuclear features, immunophenotype and ultrastructure varied and reflected that of adjacent normal mononuclear stromal cells. It is concluded that the atypical multinucleated stromal cells represent a reactive change in the indigenous stromal cells. In all the cases mast cells were seen as a prominent component of the inflammatory infiltrate and many of them were intimately related to the atypical stromal cells. It is suggested that reactive stromal cell changes may relate to an interaction with mast cells.