Collaborative Stage

Note 1: Regression is most often recognized in relation to the radial growth phase (RGP). Characteristic features include segmental absence of in-situ melanoma cells or melanoma cells with microinvasion into the papillary dermis. The papillary dermis shows patchy lymphocytic inflammation, diffuse coarse fibrosis, and collections of melanophages. Intact melanoma is usually evident on one or both sides of the area of regression. Regressive changes may be seen without residual flanking melanoma cells and (after scrutiny of multiple tissue levels) may be viewed as constituting putative complete regression of the lesion. Vertical growth phase (VGP) regression is less common and is usually seen as an area within a tumorigenic compartment that is replaced by lymphocytes and fibrosis and often also by melanophages constituting "tumoral melanosis".
Note 2: Record the primary tumor regression as documented in the pathology report. If the primary tumor regression is not identified, code regression as absent.

Code	Description
000	No regression present Regression not identified Regression absent
001	OBSOLETE DATA CONVERTED V0203 See code 010 Regression present
010	Regression present
988	Not applicable: Information not collected for this case (If this information is required by your standard setter, use of code 988 may result in an edit error.)
998	No histologic examination of primary site
999	Unknown or no information Not documented in patient record

CS Site-Specific Factor 8
Primary Tumor Regression