Circulating Tumor Material in Colorectal Cancer and Melanoma

Inclusion Criteria: * The subject must be a patient at the Hospital of the University of Pennsylvania 1. Patients with presumed stage II, III, or IV colorectal cancer with planned surgical resection of either the primary tumor or metastatic lesion(s) being evaluated at the Hospital of the University of Pennsylvania 2. Patients with histologically confirmed melanoma stage IIb, IIc, IIIa, IIIb, or IIIc/IV scheduled for surgical resection being evaluated at the Hospital of the University of Pennsylvania. * The subject must be able to provide informed consent or have an acceptable surrogate capable of giving consent on the subject's behalf. * The subject must be 18 years of age or older. Exclusion Criteria: * The subject is not able to provide informed consent.