larger defects or complete loss of staining was also noted. At these places, the boundaries between carcinomatous and sarcomatous tissue were often blurred. Conclusions: Disruption and loss of basement membranes at interface between carcinomatous and sarcomatous tissues is a frequent finding in sarcomatoid carcinomas. These changes could be consistent with an epithelial origin of the sarcomatous com- ponent in these tumors by means of an epithelial-mesenchymal conversion mechanism. Tumori, 79: 128-132, 1993 THE BASEMENT MEMBRANES IN SARCOMATOID CARCINOMAS. AN IMMUNOHISTOCHEMICAL STUDY Marcello Guarino, Salvatore Squillaci, Domenico Reale, and Giorgio Micoli (Department of Anatomical Pathology, Hospital of Treviglio) Aims: Eight sarcomatoid carcinomas from various anatomical locations were investigated by immunohistochemical staining to laminin, type IV collagen and heparan sulfate proteoglycan, to study the characteristics of basement membranes at the interface between carcinomatous and sarcomatous tissues. Methods: Paraffin wax embedded tissue sections from re- presentative 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 staining pattern were seen. In 4 cases, Key words: Sarcomatoid carcinoma, basement membranes, epithelial-mesenchymal conversion. Basement membranes (BMs) are sheet-like specialized extracellular matrices separating the epithelia from the underlying mesenchymal tissue. Albeit their composi- tion may vary in different sites, laminin, type IV col- lagen and heparan sulfate proteoglycan are present in all BMs (27). Extracellular matrix components influence many cell behaviors such as growth and differentiation, adhesion and tumor invasion (19, 20, 25). In particular, BMs playa crucial role in the maintenance of epithelial cell polarity (21) and in the regulation of tissue archi- tecture in physiologic as well as pathologic conditions (30), including tumor growth (16). During embryonic morphogenesis, BMs mediate some complex interac- tions between epithelia and neighboring mesenchymal cells (2, 8, 28) and serve as adhesive substrate for cell migration (18). Neoplastic transformation is associated with profound changes in the extracellular matrix components (19, 20). The interaction between invasive carcinoma and host stroma usually results in the formation of a more or less complete BM that separates tumor nests from stromal connective tissue (5, 6, 16, 32). Sarcomatoid carcinomas (carcinosarcomas) are biphasic tumors of uncertain histogenesis and are composed of both car- cinomatous and sarcomatous tissues (1, 12, 13, 31). Since these tumors contain epithelial as well mesenchy- Table 1 - Clinicopathologic data and results of the Immunostalnlng for BMs at the carcinoma-sarcoma Junction. Histology' BM staining pattern Case Sex/age Location Size ------------- -- ------------------- no. (yr) (ern) Carcinoma Sarcoma Focal interruptions Large defects 1 M/83 Right vocal cord 2.5 SCC Spindle +osteoid Yes Yes 2 F/62 Right vocal cord I SCC Pleomorphic Yes 3 F/45 Right/breast 1.7 ADC Spindle/pleomorphic Yes Yes 4 F/8t Left/breast 3 ADC/SCC Spindle/pleomorphic Yes 5 F/76 Right/breast 4 ADC Spindle +cartilage Yes 6 FI50 Right/breast 14 ADC Spindle/myxoid Yes Yes 7 M/80 Bladder 9 TCC Spindle Yes 8 M/82 Bladder 4 TCC Spindle/myxoid Yes Yes 1 SCc, squamous cell carcinoma; ADC, adenocarcinoma; TCe, transitional cell carcinoma. Acknowledgments: The technical assistance of Mrs. Gabriella Tadini and Mrs. Giovanna Ornaghi is gratefully acknowledged. We thank Mr. Marino Zimbaldi for preparing the figure. To whom correspondence should be addressed: Dr. Marcello Guarino, Anatomia Patologica, Piazzale Ospedale 1, 24047 Trevi- glio (Bergamo), Italy. Received February 26, 1993. 128