'Occult' breast cancer.

The aim of this paper is to explore current trends in the diagnosis, investigation and treatment of patients presenting with axillary lymph node metastases without a primary in the breast being found and, more rarely, those cases with metastatic breast cancer where the primary remains unknown--the so-called, 'occult' breast cancer. A retrospective study of 25 reported cases were selected from our database at the Royal Marsden and 6 patients were found to have true 'occult' breast cancer. These 6 patients are all still alive with no primary ever having been found in the breast. A literature review was then undertaken exploring the changing trends in this diagnostic enigma. MRI scanning, it is reported, may reveal the primary. Occult cancers in which imaging totally fails to show the primary will become increasingly rare. The prognosis of these, however, may be surprisingly better than one would expect from the nature of their presentation.