Desmoplastic basal cell carcinomas possess unique basement membrane-degrading properties

Desmoplastic basal cell carcinomas (fibrosing or morphea types) were studied ultrastructurally, immunocytochemically, and biochemically for basement membrane-degrading activity and compared with the common varieties of basal cell (superficial and nodular-ulcerative types). Whereas the latter lesions demonstrated intact basement membranes as evidenced by extracellular laminin and type IV collagen immunoreactivity and the presence of an unusually thickened basal lamina, desmoplastic basal cell carcinomas showed large defects and absences in basal lamina and basement membrane immunoreactivity. Intense tumor cytoplasmic immunoreactivity for type IV collagenase was present in 13 of 15 cases of desmoplastic basal cell but absent in the superficial and nodular-ulcerative varieties. Whereas explant cultures of all the types of basal cell carcinoma studied gave rise to high levels of interstitial (type I) collagenase activity in conditioned media, only the desmoplastic variety exhibited high type IV collagenase activity. These findings suggest that the mechanisms by which the desmoplastic and the common varieties of basal cell carcinoma infiltrate host tissues may be fundamentally different.