Epithelioid and biphasic mesothelioma make up approximately 75-95% of mesotheliomas and have been well characterized histologically, whereas sarcomatous mesothelioma has not been studied extensively. Most mesotheliomas express high levels of cytokeratin 5 regardless of subtype.Epithelioid mesothelioma is characterized by high levels of calretinin.Sarcomatous mesothelioma does not express high levels of calretinin.Other morphological subtypes have been described:

Desmoplastic
Clear cell
Deciduoid
Adenomatoid
Glandular
Mucohyaline
Cartilaginous and osseous metaplasia
Lymphohistiocytic

Differential diagnosis
Metastatic adenocarcinoma
Pleural sarcoma
Synovial sarcoma
Thymoma
Metastatic clear cell renal cell carcinoma
Metastatic osteosarcoma

Staging
Staging of mesothelioma is based on the recommendation by the International Mesothelioma Interest Group. TNM classification of the primary tumor, lymph node involvement, and distant metastasis is performed. Mesothelioma is staged Ia–IV (one-A to four) based on the TNM status. Prevention
Mesothelioma can be prevented in most cases by preventing exposure to asbestos. The US National Institute for Occupational Safety and Health maintains a recommended exposure limit of 0.1 asbestos fiber per cubic centimeter. Screening
There is no universally agreed protocol for screening people who have been exposed to asbestos. Screening tests might diagnose mesothelioma earlier than conventional methods thus improving the survival prospects for patients. The serum osteopontin level might be useful in screening asbestos-exposed people for mesothelioma. The level of soluble mesothelin-related protein is elevated in the serum of about 75% of patients at diagnosis and it has been suggested that it may be useful for screening. Doctors have begun testing the Mesomark assay, which measures levels of soluble mesothelin-related proteins (SMRPs) released by mesothelioma cells. Treatment
Mesothelioma is generally resistant to radiation and chemotherapy treatment. Long-term survival and cures are exceedingly rare.
Peutz–Jeghers syndrome (often abbreviated PJS) is an autosomal dominant genetic disorder characterized by the development of benign hamartomatous polyps in the gastrointestinal tract and hyperpigmented macules on the lips and oral mucosa (melanosis). This syndrome can be classed as one of various hereditary intestinal polyposis syndromes and one of various hamartomatous polyposis syndromes. It has an incidence of approximately 1 in 25,000 to 300,000 births. Signs and symptoms
The risks associated with this syndrome include a substantial risk of cancer, especially of the breast  and gastrointestinal tracts. Colorectal is the most common malignancy, with a lifetime risk of 39 percent, followed by breast cancer in females with a lifetime risk of 32 to 54 percent.Patients with the syndrome also have an increased risk of developing carcinomas of the liver, lungs, breast, ovaries, uterus, testes, and other organs. Specifically, it is associated with an increased risk of sex-cord stromal tumor with annular tubules in the ovaries.Due to the increased risk of malignancies, direct surveillance is recommended.The average age of first diagnosis is 23. The first presentation is often bowel obstruction or intussuseption from the hamartomatous gastrointestinal polyps. Dark blue, brown, and black pigmented mucocutaneous macules, are present in over 95 percent of individuals with Peutz-Jeghers syndrome. Pigmented lesions are rarely present at birth, but often appear before 5 years of age. The macules may fade during puberty.