Clinical findings:
(1) history of smoking
(2) negative family history of thrombosis
(3) negative personal history for thrombosis
(4) advanced age
(5) constitutional symptoms (weight loss, fever, sweating)
(6) resistance to anticoagulant therapy
(7) tendency to relapse
(8) migrating thrombosis
(9) presence of both deep and superficial venous thrombosis
(10) presence of upper limb thrombosis
(11) presence of a silent DVT in the contralateral limb
Laboratory findings:
(1) anemia
(2) thrombocytosis
(3) increased ESR
(4) increased LDH
(5) increased alkaline phosphatase
(6) high levels of tumor markers (CEA, PSA, etc.)
A complete workup is indicated when several of these findings are present.
Some things that I might add to this list:
(1) history of a cancer in the past
(2) family history of malignant disease
(3) unexplained fracture or bone pain
(4) lung mass on chest X-ray
