Peritoneal cancer of unknown origin
Some patients present symptoms of a peritoneal cancer that has an unknown origin. The tumor characteristics show the peritoneal cancer must have metastasized from another type of cancer in the body (e.g., colorectal cancer), but the primary tumor cannot be found despite thorough examinations. This type of peritoneal cancer is usually very frustrating both for the patient and for the treating physician. An unknown origin also hampers treatment possibilities, and the small number of available treatment options is probably one of the reasons the prognosis for these patients is usually very bad.
In patients in a good general condition, it is important to undertake every effort to identify the primary tumor whenever possible. Sometimes a treatable condition such as appendiceal or ovarian cancer may be identified after all. Only in these very select patients may HIPEC treatment offer some benefit. HIPEC is usually not considered in other cases but some patients may benefit from systemic chemotherapy.
In conclusion, PM from an unknown primary tumor currently has a very bad prognosis. However, because effective treatments are now available for select patient categories, every effort should be undertaken to identify the primary tumor whenever possible. Potentially effective treatment strategies should also be further explored for patients in whom the origin of the cancer is unknown.