[The obscure primary tumor]

The imaging techniques and their results were analysed in 202 patients in whom a primary tumour was diagnosed only at autopsy. The main cause for failure to find the primary tumour was misinterpretation by the radiologist. Pure description offers no more than can be seen by a skilled clinician. The examination should lead to a diagnosis; even a suspicion should be indicated and one should insist on additional measures for follow-up or for obtaining a diagnosis. Improved diagnosis due to the introduction of sonography and CT has only been partially achieved. Malignant pulmonary tumours are the most commonly overlooked lesions and represent 30% of undiagnosed tumours. They are the most frequent primary tumours giving rise to cerebral and bone metastases.