The value of immunohistochemistry in increasing diagnostic precision of undifferentiated tumours by the surgical pathologist.

The availability of polyclonal and monoclonal antibodies allows immunohistochemical staining (immunofluorescence and immunoperoxidase) procedures to be used by the surgical pathologist, so as to obtain a definite diagnosis in cases where light microscopic examination of tissue sections from biopsy and surgical specimens in inconclusive. Four cases of undifferentiated tumours are described in which only a differential diagnosis could be obtained using light microscopy but a definite diagnosis was achieved when additional information was provided by immunohistochemistry. A scheme is presented for the use of immunohistochemistry to increase diagnostic precision in assessing tumours.