The extracellular matrix in skin tumor development - a morphological study

The development of cancer involves epithelial-stromal interactions. Alterat ions in the synthesis and deposition of type I and III collagens are relate d to the tumor morphology. Skin carcinogenesis in experimental animals prov ides a reliable model for the development of neoplasia. Ultraviolet (UV) ir radiation is the main etiological factor for epidermal dysplasia and malign ant tumors in man, but also for dermal degeneration Non-neoplastic dermal c hanges and skin tumors induced by ultraviolet irradiation and 7,12-dimethyl benz(a)anthracene were investigated in various mouse strains with different susceptibilities to tumor formation. UVB irradiation resulted in an increa sed immunoreactivity of collagens in the dermis, in comparison with 7,12-di methylbenz(a)anthracene. Increased synthesis and deposition of type I and I II collagens were found in the stroma adjacent to benign alterations. In we ll-differentiated squamous cell carcinomas, a similar induction of collagen synthesis and deposition was observed. The destruction of fibrillary struc tures was more pronounced during the decrease of differentiation from moder ately to poorly differentiated squamous cell carcinomas. Anaplastic carcino mas with spindle cell morphology displayed a delicate meshwork of reticular fibers and collagen III, and abnormal expression of mRNA for collagens in some malignant cells with epithelial characteristics. The underlying stroma reacts to the development of epithelial tumors in a reproducible way, whic h is related to the carcinogenic agent involved.