The frequency of somatic mutations and deletions of PTEN/MMAC1 in melanoma resection specimens is controversially discussed so far: Microsatellite analyses demonstrated LOH at the PTEN/MMAC1 locus in none of 23 primary cutaneous and 17 metastatic melanomas (0%; Böni et al, 1998), in a single of 10 investigated melanomas (10%; Steck et al, 1997), in two of 44 informative primary and metastatic melanomas (4%; Herbst et al, 1999) and in three of eight primary and in 18 of 31 metastatic melanomas (3 and 58%, respectively; Birck et al, 2000). This evidence concerns the gene PTEN and metastatic melanoma.