Eligibility Criteria:

1. Age 18 years or older.
2. Confirmed histological or cytological diagnosis of a malignant solid tumor that is either specified in one of the pre-defined tumor cohorts or meets the enrollment criteria for the Mix of Solid Tumors (MOST) cohort (Table 1).

3. Eligible for curative intent therapy, with surgical resection of cancer planned.

   a. If surgical resection has occurred, enrollment should occur within 3 months of surgical resection and before initiation of adjuvant therapy.

4. Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0, 1, or 2.
5. No systemic therapy for current cancer diagnosis administered before enrollment.
6. Willing and able to comply with required study procedures, including blood sample collection and primary tumor tissue submission from diagnostic biopsy or surgical excision.
7. Has completed all therapy (including endocrine therapy) 3 or more years ago for any previous invasive solid organ malignancy (with exception of nonmelanoma skin cancers) or hematologic malignancy. Individuals with a prior history of noninvasive (in situ) carcinomas may participate if they have received definitive treatment (no washout period required).
8. No concurrent diagnosis of another invasive cancer, except for nonmelanoma skin cancers.
9. No prior allogeneic hematopoietic stem cell transplant.

10. Able and willing to provide informed consent and Health Insurance Portability and Accountability Act (HIPAA) authorization for the release of personal health information.

    Cohort Specific Criteria

11. Muscle-invasive urothelial carcinoma of the bladder and Melanoma Cohorts: Stage II or operable III cancer:
12. Esophageal, Gastric/GEJ, and NSCLC Cohorts: Stage I, II, or operable III cancer.
13. Pancreatic Cohort: Stage I, II or operable III cancer, exocrine only disease.
14. MOST cohort: Stage II or operable stage III solid tumor diagnosis that meets eligibility criteria and is not included in the other cohorts.

The following tumor types are excluded:

1. Central nervous system (CNS) malignancies
2. Colorectal cancer
3. Breast cancer
4. Squamous cell skin cancer
5. Basal cell carcinoma
6. Gastrointestinal stromal tumors (GIST)
7. Thyroid cancer
8. Uveal melanoma

9. Low or intermediate grade neuroendocrine tumors

   ■ Eligible tumor types: High-grade neuroendocrine tumors, including neuroendocrine carcinomas, Merkel cell carcinomas, and small cell lung cancer are permissible

10. Hematologic cancers including multiple myeloma or other plasma cell dyscrasias, Hodgkin's lymphoma, non-Hodgkin's lymphoma, acute or chronic leukemias including chronic lymphocytic leukemia / small lymphocytic leukemia