EXPRESSION OF 2 MORPHOLOGIC PARAMETERS CONCERNING TUMOR-STROMA INTERACTION IN BENIGN AND MALIGNANT MELANOCYTIC SKIN-LESIONS

The importance of tumor-stroma interaction in many solid tumors of the skin has been demonstrated in recent years. Invasion and metastasis r equire multiple interactions of the tumor cells with the surrounding s troma. In malignant melanoma most studies concerning tumor-stroma inte raction focus on the peritumoral infiltrate, whereas other aspects of tumor-stroma interactions have not been considered. We investigated tw o morphologic criteria of tumor-stroma interaction in melanocytic skin tumors. Simple infiltration into the surrounding dermis or subcutis w ithout evident stromal reaction (DERMSIMPLE) and the existence of morp hologically intact collagen bundles of the reticular dermis within the tumor bulk (PRECOLL) were examined in 373 benign common nevi, 239 dys plastic nevi, 322 Spitz nevi, 368 primary malignant melanomas, and 344 melanoma lesions metastatic to the skin. Our results showed that ther e is a highly significant difference in the expression of DERMSIMPLE a nd PRECOLL between benign and malignant melanocytic skin tumors. Conce rning DERMSIMPLE, 13.3% of benign skin lesions compared with 28.2% of malignant lesions were positive for this feature; PRECOLL was found in 13.8% benign and 37.1% malignant lesions (chi-squared test; p = 0.000 1 for both features). Furthermore, it could be demonstrated that simpl e infiltration into the surrounding stroma as well as the existence of morphologically intact collagen bundles of the reticular dermis withi n the tumor bulk increases with tumor progression; between primary mal ignant melanoma and melanoma metastatic to the skin, for example, ther e was a highly significant difference for DERMSIMPLE, as well as for P RECOLL (chi-squared test; p = 0.00001). These data indicate that morph ologic aspects of tumor-stroma interactions in different benign and ma lignant melanocytic skin lesions may reflect biological behavior of tu mor cells. The analysis of further aspects of tumor-stroma interaction and the relation to the patient's outcome may lead to the development of further prognostic parameters in malignant melanoma.