MMP1 and mast cell neoplasm: Since this collagenase is supposed to promote the tumor growth during the early stages of tumor progression and cannabinoids have been demonstrated to be able to stimulate the tissue inhibitor of MMP-1, the authors hypothesized that the simultaneous high CB2R and MMP-1 expression suggests a possible use of cannabinoids as an antitumoral target in low-grade cutaneous canine mast cell tumors [19].