Background: The significance of regression in primary melanoma has been disputed for many years. Some have suggested regression as a marker for poor prognosis while others have reported a negligible or even a favourable effect, on prognosis.
Aim: The aim was to understand the significance of regression in melanoma and provide further information on whether patients should be subjected to a SLNB on the basis of regression.
Methods: 146 melanoma cases who had undergone a sentinel lymph node biopsy were included in the study. The histological criteria for offering SLNB was melanomas more than 1mm in thickness, or Clark’s level IV or those with regression. Since the definition of regression is subject to variation this aspect was defined in detail.
Results: There is a statistically significant greater proportion of individuals without regression that show SLN positivity (p=0.028) compared with those which do show regression. Metastatic disease was found to correlate with growth phase of the primary lesion.All the node positive cases were in the vertical growth phase whilst none of the cases in radial growth phase and showing regression were associated with nodal metastasis (p=0.029). Out of our total of 146 cases, 62 cases had melanomas with thickness less than 1mm or were in radial growth phase yet were offered sentinel node biopsy because of regression. Of these 62 cases 44 showed features of regression and all were node negative. The remaining 16/62 cases of thin melanomas did not show regression and two out of these 16 cases had sentinel node metastasis. These findings suggest that regression is a good prognostic factor especially in thin melanomas. The proportion of the primary lesion involved with regression and the thickness of the regression did not correlate with the SLN status. Other factors which did correlate with the SLN status included the thickness of the primary and the mitotic count.
Conclusion: Our findings suggest that regression is usually a favourable process particularly in thin melanomas and that metastasis in "thin melanomas showing regression" is real but rare. Variant vertical growth phase , mitoses and other prognostically significant variables may be more important predictors of metastatic potential in thin melanomas.
- Sentinel lymph node