A potential source of false-positive sentinel nodes: immunostain misadventure.

The clinical and pathologic aspects of sentinel lymph node biopsy have generated much attention. Pitfalls in the pathologic handling of sentinel lymph node specimens have received little attention. We report a case in which a false-positive diagnosis might have been rendered on a sentinel lymph node because of an inadvertent immunostaining error. Attention was drawn to the problem by an unusual pattern of distribution of immunoreactive cells-which proved to be plasma cells rather than metastatic carcinoma cells.