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 microinvasive 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 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 recorded in the pathology report. If the primary tumor regression is "not identified" the registrar should code as absent.

Code	Description
000	No regression present Regression not identified Regression absent
001	Regression present
988	Not applicable: Information not collected for this case
998	No histologic exam of primary site
999	Unknown Not stated Not documented in patient record

CS Site-Specific Factor 8
Primary Tumor Regression