MMP9 and pachyonychia congenita: Since PC-3 xenograft tumors have a high metastatic potential[30-32] and the degradation of ECM proteins by MMP-9 may facilitate metastasis[21], we analyzed the size of lumbar and renal lymph nodes in PC-3 tumor bearing mice, as these have been shown to be colonized by tumor cells, and increased in size compared to healthy ones[6].