Malignant mesothelioma is a rare malignancy with limited therapeutic options and its incidence is still increasing in both Europe and the developing nations. Symptoms and signs associated with mesothelioma are nonspecific and elusive, often seen with other disease processes (either benign or malignant) and the condition itself sometimes appears more than 40 years after exposure.

Typical clinical presentation

Early symptoms of malignant mesothelioma can be nonspecific and often caused by the cancer growing and subsequently pressing on a nerve or other body organs. In the majority of cases the disease is diagnosed in advanced stages, as considerable time is needed to arrive at the correct diagnosis.

Cardinal presenting features of pleural mesothelioma are chest pain, dyspnea or both. They can be confused with pneumonia or asthma, or some other respiratory ailments. Breathlessness due to a pleural effusion without chest pain can be observed in one third of the patients.

Involvement of the mediastinal structures in pleural mesothelioma is well established, although voice hoarseness and superior vena cava obstruction seldom cause major symptoms. Some patients develop splinting and scoliosis on the side of mesothelioma. Dysphagia can also occur but often represents a late finding.

Pleural effusions are common and on the right side 60% of the time (bilateral effusions occur in 5% of the cases). Palpable soft tissue mass and decreased respiratory sounds are accompanying manifestations. Pleural plaques are also a frequent sign of the disease, with 20% of affected individuals developing bibasilar fibrosis (a characteristic sign of chronic asbestosis).

Peritoneal mesothelioma demonstrates a wide spectrum of biological aggressiveness, and the scarcity of symptoms early in the disease results with a majority of patients diagnosed when the malignancy is already diffusely spread throughout abdomen and pelvis. Compression of the gastrointestinal tract can further complicate the disease, but rarely acts as the presenting symptom.

The most frequent initial symptoms are abdominal pain and swelling, diarrhea, poor appetite, marked weight loss and ascites. Night sweats, thrombophlebitis and hypercoagulability occur less frequently, and fever of the unknown origin, intestinal obstruction or acute inflammatory lesions that warrant urgent surgical approach have also been reported.

Several paraneoplastic syndromes are associated with mesothelioma, which include thrombocytosis, hypocalcemia, hypoglycemia, venous thrombosis, autoimmune hemolytic anemia, paraneoplastic hepatopathy, hypercoagulable states, disseminated intravascular coagulation and a wasting syndrome.

Staging of mesothelioma

According to the WHO classification, malignant mesothelioma is classified as epithelioid, sarcomatoid or biphasic, depending on the pathohistiological analysis of the tissue. A number of staging systems have been suggested for malignant mesothelioma, but currently the International Mesothelioma Interest Group TNM staging system for pleural mesothelioma has the widest implementation. There is no established staging system for peritoneal mesothelioma.

The TNM system describes the size and position of the mesothelioma primary tumor (T), eventual spread of mesothelioma cells to nearby lymph nodes (N) and eventual metastatic spread of mesothelioma cells to other parts of the body (M). Once the TNM categories have been decided, the information is grouped together to give the stage, with stage 1 being the earliest and stage 4 the most advanced stage.