regression in melanoma

Definition : Histologic evidence of partial regression is seen in 10-35% of primary cutaneous melanomas. In a small number of cases, melanomas regress completely after giving rise to nodal or distant metastases. In 5-15% of cases of metastatic melanoma, the primary tumor is never found, presumably due to complete regression.

Images

 https://www.webpathology.com/image.asp?n=35&Case;=1025