Study of Circulating Cancer Cells in Patients With Metastatic Breast, Ovarian, Colon, or Pancreatic Cancer

RATIONALE: Counting the number of circulating cancer cells in samples of blood from patients with metastatic cancer may help doctors find out how much the cancer has spread.
PURPOSE: This research study is looking at the number of circulating cancer cells in patients with metastatic breast cancer, ovarian cancer, colon cancer, or pancreatic cancer.