Polyarthritis can rarely (<2%) be the presenting manifestation of an occult malignancy. The association of polyarthritis and malignancy is suggested by:
A close temporal relationship between the onset of a seronegative arthritis and the diagnosis of malignancy.
Improvement of the arthritis with treatment of the underlying cancer.
Recurrence of the arthritis with tumor recurrence.
Carcinomatous polyarthritis should be strongly suspected in a patient with the following features:
Explosive onset of an asymmetric oligoarthritis or polyarthritis
Late age of onset
Predominant lower extremity involvement
Radiographs show no periosteal reaction. Note that polymyalgia rheumatica-like symptoms unresponsive to prednisone have also been described as a presentation of various malignancies.