Fallopian tube cancer occurs when there is abnormal cell proliferation in the fallopian tube. These cells were initially normal; however, due to certain pathogenic factors, they have acquired certain characteristics that allow them to divide indefinitely to form a malignant growth. In early stage of the cancer, the cancer cells are confined inside the tube. Over time, however, some cells can migrate from their original place and form new tumor in other tissues or organs (metastatic fallopian tube cancer).
However, it is very rare that the cancer develops directly in the fallopian tubes. In most cases, fallopian tube cancer is a metastasis; the cancer comes from another malignant tumor that started elsewhere in body, mainly the ovaries, endometrium, GI tract, peritoneum, or the breasts.