Spectrum of morphologic alterations of regression in cutaneous melanoma--potential for improving disease prognosis

Regression occurs as a complex interaction between tumor cells and host's immune response; neither biologic mechanisms, nor regression prognostic significance are deciphered to date but promising anti-cancer vaccine strategies were thus developed. We analyzed 127 superficial spreading melanomas identifying melanoma with regression (segmentary (SR), partial (PR) and segmentary & partial (SR-PR)) or without regression (AR). Several histopathologic parameters were registered; statistical analysis was performed (level of significance P < 0.05). Regression was present in 52% cases, less frequently in pT4 melanomas. Ulceration and vascular invasion were similarly present in pT2-pT4 melanomas with regression and significantly less in pT1 ones; their incidence increased with stage in AR (P < 0.001). SR and SR-PR melanomas showed significantly more tumor infiltrating lymphocytes within the non-regressed tumor than AR melanomas (P < 0.05). SR melanomas presented significantly less frequent mitoses than PR (P = 0.04), SR-PR (P = 0.04) or AR ones (P = 0.03). Marked inflammation and more numerous melanophages were present regressed areas advanced stage melanomas. More numerous plasma cells were identified in advanced stages; in SR and SR-PR melanomas less numerous plasma cells were present in pT1 than in advanced stages. Vascular hyperplasia was significantly higher in SR than SR-PR cases. Differences in perception of regression might be the result of labeling with similar name of various processes comprising inflammation and tumor cells destruction; at least in thin melanomas, PR and SR seem to belong to different spectrum of alteration, SR bearing a more favorable potential. Further studies will be performed in order to further elucidate the mechanisms involved in regression in melanoma.