Cancers of unknown origin represent approximately 5% of all
cancers and are therefore as frequent as some solid
tumors such as gastric or
pancreatic cancers. The diagnosis of
cancer of unknown origin should be based on a detailed pathological examination including immunohistochemical techniques and electron microscopy; hormonal receptors should also be measured. Besides detailed medical history and physical examination, only a few additional tests should be carried out: routine chemistry including the assay of HCG, alphafoetoprotein and specific
antigen of the prostate, chest X-ray, thyroid scan, mammography and abdominal CT scan. Other tests are generally not of sufficient specificity and sensitivity.
Unknown primary tumors arising in the cervical area are frequently
squamous cell carcinomas corresponding to occult primary
tumors of the upper aerodigestive mucosae and are efficiently treated by cervicofacial
radiotherapy or
lymph node dissection. Women presenting with axillary lymph nodes with no obvious primary
tumor should be treated according to the guidelines used for
breast cancer. The patients with inguinal lymph nodes of unknown origin are usually treated with
radiation therapy. The syndrome of germinal
tumors of extragonadic origin corresponds to cases of undifferentiated or poorly differentiated
carcinomas in patients under 50 years of age and with one of the following characteristics: involvement of the median organs, lung involvement, lymph node involvement or increase of alphafoetoprotein or HCG. The therapeutic approach recommended for these patients consists of the chemotherapeutic combination used for
testicular cancer. For all other patients, the prognosis remains poor. Patients with local symptoms may be treated by
radiation therapy; others may receive a combination of
fluorouracil,
doxorubicin and
mitomycin.