How common is it for a blood clot to be diagnosed before doctors detect an underlying cancer?

Occassionally: When a patienthas breathingproblems and a scan shows evidence of a pulmonary embolus or clot to lung, work up may show a pelvic lesion that was unsuspected. At times other forms of thrombosis can be due to a tail of pancreas cancer unsuspected until work up defines it. On most other occussions the clot occurs after management of a known malignancy