The microfilament-associated
protein vinculin is a major constituent of muscle tissue localized in costameres and Z-discs of the sarcomeric apparatus, where it is thought to play a pivotal role in the alignment of sarcomeric myofibrils and the transduction of mechanical force between the internal contractile machinery and the extracellular environment. In order to investigate whether anti-
vinculin antibodies are helpful in confirming the commitment of
rhabdomyosarcomas to the myogenic pathway, we studied immunohistochemically the expression pattern of
vinculin in a series of 7 human
rhabdomyosarcomas including those of embryonal, botryoid, and pleomorphic subtypes. Using
monoclonal antibody from clone hVIN-1 by APAAP techniques on
formalin-fixed,
paraffin-embedded tissue, all but one
tumor, which was a primitive
embryonal rhabdomyosarcoma, demonstrated a significant positive
vinculin staining.
Vinculin expression was most prominent in differentiated
tumors with a focal staining pattern showing a high degree of correlation with rhabdomyoblasts, whereas a diffuse staining was observed in areas in which small, poorly differentiated
tumor cells alone were present. Since
vinculin immunoreactivity could also be demonstrated in cases of
leiomyosarcoma, the positive immunohistochemical detection of
vinculin was not exclusively restricted to mesenchymal
tumors derived from sarcomeric muscle tissue. Immunodetectable amounts of
nebulin could be revealed only in two
embryonal rhabdomyosarcomas. Our results suggested that the positive identification of
rhabdomyosarcoma achieved by using
antibodies against
vinculin in addition to other known myogenic markers may be particularly useful in the differential diagnosis of anaplastic, poorly differentiated
sarcomas.