Aims: Eight sarcomatoid carcinomas from various anatomical locations w
ere investigated by immunohistochemical staining to laminin, type IV c
ollagen and heparan sulfate proteoglycan, to study the characteristics
of basement membranes at the interface between carcinomatous and sarc
omatous tissues. Methods: Paraffin wax embedded tissue sections from r
epresentative tumor samples have been stained with specific antibodies
, using the peroxidase-antiperoxidase technique. Results: In all cases
several interruptions or discontinuities of the basement membrane sta
ining pattern were seen. In 4 cases, larger defects or complete loss o
f staining was also noted. At these places, the boundaries between car
cinomatous and sarcomatous tissue were often blurred. Conclusions: Dis
ruption and loss of basement membranes at interface between carcinomat
ous and sarcomatous tissues is a frequent finding in sarcomatoid carci
nomas. These changes could be consistent with an epithelial origin of
the sarcomatous component in these tumors by means of an epithelial-me
senchymal conversion mechanism.