Role of total-body computed tomography and 18-fluorine-fluorodeoxyglucose positron emission tomography/ computed tomography scan in malignant pleural effusion patients with unknown primary tumor site

Malignant pleural effusion (MPE) is defined by the presence of neoplastic cells in the pleural fluid, and it can occur during multiple malignancies; lung and breast cancer are the main responsibles. However, about 11% of MPE are determined by cancer of unknown primary (CUP) site. CUP is a malignant widespread metastatic disease without an identified primary site despite sweeping medical and radiological evaluation. It is known that CUPs are related to poor prognosis with a low life expectancy. The management of MPE from unknown primary tumor site represents an important medical challenge also because there are no protocols or “ad hoc” guidelines. Total body positron emission tomography/computed tomography (PET/ CT) and CT scan in the diagnostic path of CUP has been well-defined, but the Literature is poor regarding their use in the evaluation of MPE associated with CUP. This review tries to achieve a conclusion on the role of CT scan and PET/CT in MPE with CUP by comparing the most recent clinical studies.