What are the other Names for this Condition? (Also known as/Synonyms)

• WDPM (Well-Differentiated Papillary Mesothelioma)
• Well-Differentiated Papillary Type of Mesothelioma of Uncertain Malignant Potential
• Well-Differentiated Papillary Type of Mesothelioma of Undetermined Malignant Potential

What is Well-Differentiated Papillary Mesothelioma? (Definition/Background Information)

• A mesothelioma is a tumor of the mesothelial cells (membrane lining the various body cavities). They are known to mostly arise in the pleura and peritoneum, and rarely, in the pericardium, the tunica vaginalis of testis, and ovary
• Well-Differentiated Papillary Mesothelioma (WDPM) is rare histological variant of epithelial mesothelioma. In this subtype, the tumor cells have papillary architecture. The tumor is diagnosed under a microscope, on examination of the cancer cells by a pathologist
• The cytology of cells is often bland; it does not spread to surrounding tissue and distant areas. Hence, the behavior of this tumor is predominantly benign. In some cases, WDPM has a chance of becoming malignant, and hence, it is also called Well-Differentiated Papillary Type of Mesothelioma of Uncertain Malignant Potential
• Unlike most malignant mesotheliomas, the benign Well-Differentiated Papillary Mesothelioma is not associated with asbestos exposure. The cause of formation of the tumor is not well-established
• The tumor can be found in the pleura or pericardium, but most cases are observed in the peritoneal cavity (abdomen). The signs and symptoms depend upon the location of the tumor. Small-sized tumors during the initial stages may remain asymptomatic
• Large-sized Well-Differentiated Papillary Mesotheliomas can cause pain, obstructive symptoms, fatigue, and weight loss. However, no invasion into the surrounding tissue is noted in a majority of cases
• The treatment of Well-Differentiated Papillary Mesothelioma is undertaken through a surgery. Usually treatment measures such as chemotherapy and/or radiation therapy is not required. The prognosis is generally excellent with complete surgical excision and removal of the tumor

Who gets Well-Differentiated Papillary Mesothelioma? (Age and Sex Distribution)

• Well-Differentiated Papillary Mesothelioma is a rare and mostly benign histological subtype of epithelial mesothelioma
• The tumor may occur in a wide age range of adults in the 20-75 year age group; the mean age of presentation, according to some studies, is around 47 years
• Both males and females are affected, although the tumor incidence is more in females than males
• No racial or ethnic group preference is generally noted

What are the Risk Factors for Well-Differentiated Papillary Mesothelioma? (Predisposing Factors)

Currently, no definitive risk factors are noted for the development of Well-Differentiated Papillary Mesothelioma. But it may be associated with the following factors:

• Iatrogenic tumors: Some tumors have been reported to form following medical treatment for angina pectoris; for tumors affecting the pericardium
• Chronic smoking
• In rare cases, treatment for breast or abdominal cancer using radiation therapy is also known to cause the formation of malignant mesothelioma
• Exposure to eronite, a type of naturally-occurring mineral fiber, in some parts of the world (e.g. Turkey), may be a risk factor
• Family history of mesothelioma: Mutations in BAP1 gene that can run in some families can increase the risk for malignant mesothelioma. The gene mutation can also cause an increased risk for a variety of cancers, such as ocular melanoma, clear cell renal cell carcinoma, liver cancer including intrahepatic cholangiocarcinoma, melanoma of skin, etc. in such individuals

Note: In some cases, no association to any of the above factors may be identified.

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Well-Differentiated Papillary Mesothelioma? (Etiology)

• The exact cause and mechanism of formation of Well-Differentiated Papillary Mesothelioma is unknown. Mesotheliomas have been shown to have a variety of different genetic mutations
• A vast majority of the tumors are predominantly benign variant of mesothelioma, while rarely, some are known to be aggressive
• However, among the benign mesothelial tumors, WDPM has the highest chance of becoming malignant, and so, it is termed as a benign tumor of uncertain malignant potential

What are the Signs and Symptoms of Well-Differentiated Papillary Mesothelioma?

The signs and symptoms of Well-Differentiated Papillary Mesothelioma depend upon the location of the tumor. These may include:

• The presence of large-sized tumors that are nodular in appearance
• The tumor can be localized to one area or can be multifocal (arising from 2 or more locations)
• Well-Differentiated Papillary Mesothelioma is a slow-growing tumor that is mostly observed in the peritoneum (abdomen). The other sites of involvement include the pleura (lung), pericardium (heart), and the tunica vaginalis of testis
• In and around the peritoneal region, the tumor may be seen at the following locations:
  • Omentum
  • Uterine serosa
  • Small bowel mesentery
  • Fallopian tube
  • Ovary
  • Stomach serosa
• Low-grade fever and profuse sweating
• Tiredness or fatigue
• Tumors in the pleura or pericardium can lead to:
  • Shortness of breath or rapid breathing
  • Pleural or pericardial effusion; an abnormal collection of fluid within the pleura/pericardium
  • Chest pain or discomfort, such as feelings of heaviness/fullness of the chest
  • Intermittent cough
  • Tumors in the heart or lung can spread and obstruct major blood vessels or airways
• Tumors in the peritoneum can lead to:
  • Abdominal pain; swollen abdomen
  • Nausea and vomiting
  • Change in bowel habits
  • Ascites; an abnormal collection of fluid within the abdominal cavity
• Fainting or feeling faint, dizziness
• Swelling in the lower legs
• Weight loss

There are no signs and symptoms during the initial stages of tumor growth and development. Also, small-sized tumors usually do not cause any symptoms. But, occasionally they may become painful, if the surrounding structures are compressed.

How is Well-Differentiated Papillary Mesothelioma Diagnosed?

The following tools may be used towards establishing a diagnosis of Well-Differentiated Papillary Mesothelioma:

• Complete evaluation of family (medical) history, along with a thorough physical examination
• X-ray of the affected region
• CT or CAT scan with contrast of the affected region may show the presence of a mass. This radiological procedure creates detailed 3-dimensional images of structures inside the body
• MRI scans of the affected region: Magnetic resonance imaging (MRI) uses a magnetic field to create high-quality pictures of certain parts of the body, such as tissues, muscles, nerves, and bones. These high-quality pictures may reveal the presence of the tumor
• Whole-body PET scan, bone scan of affected region to check for tumor metastasis. This helps with the staging of the tumor

Although the above modalities can be used to make an initial diagnosis, a tissue biopsy of the tumor is necessary to make a definitive diagnosis to begin treatment. The tissue for diagnosis can be procured in multiple different ways which include: 

• Fine needle aspiration (FNA) biopsy of the tumor: A FNA biopsy may not be helpful, because one may not be able to visualize the different morphological areas of the tumor. Hence, a FNA biopsy as a diagnostic tool has certain limitations, and an open surgical biopsy is preferred
• Core biopsy of the tumor
• Open biopsy of the tumor

Tissue biopsy of the tumor:

• A biopsy of the tumor is performed and sent to a laboratory for a pathological examination. A pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. Examination of the biopsy under a microscope by a pathologist is considered to be gold standard in arriving at a conclusive diagnosis
• Biopsy specimens are studied initially using Hematoxylin and Eosin staining. The pathologist then decides on additional studies depending on the clinical situation
• Sometimes, the pathologist may perform additional studies, which may include immunohistochemical stains, electron microscopy, and molecular studies to assist in the diagnosis

Note:

• It is rare to find a tumor that has purely one subtype. Often, there is a mixture of more than one cell type. The predominant pattern determines the histological subtype of the tumor
• Due to the rarity of these tumors, the diagnosis of this tumor can be missed. It can even cause diagnostic challenges during a frozen section biopsy

A differential diagnosis may have to be undertaken to eliminate the following tumor types or conditions prior to arriving at a definitive diagnosis:

• Adenomatoid tumor
• Benign mesothelial hyperplasia
• Malignant mesothelioma
• Papillary endosalpingiosis
• Peritoneal carcinomatosis
• Reactive mesothelial hyperplasia
• Serous papillary carcinoma of the ovary/peritoneum
• Serous tumor of low malignant potential of peritoneum
• Tuberculous peritonitis

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Well-Differentiated Papillary Mesothelioma?

Complications due to Well-Differentiated Papillary Mesothelioma are dependent upon the site of the tumor and could include the following:

• Pleural tumors may result in:
  • Large tumors can obstruct the bronchus (airways) and other adjoining organs/structures
  • Severely impaired lung function
• Pericardial tumors may result in:
  • Congestive heart failure, depending on the location of the tumor in the heart
  • Cardiac tamponade due to fluid around the pericardium, which can lead to low blood pressure, fatigue, anxiety, rapid breathing, and fainting
  • Increased risk for thromboembolism (blood clot obstructing a blood vessel) 
• Large tumors can compress adjoining organs and structures and impair their function
• Recurrence of the tumor after surgery, when the entire tumor is not removed
• Among all benign mesotheliomas, the WDPM type has the greatest chance of undergoing a malignant transformation; However, whether they turn malignant or not is currently unclear
• Blood loss during invasive treatment methods may be heavy
• Damage of vital nerves, blood vessels, and surrounding structures during surgery

Local infiltration into the surrounding tissues or organs, and spread of the tumor to other sites in the body is generally not observed.

How is Well-Differentiated Papillary Mesothelioma Treated?

In general, the Well-Differentiated Papillary Type of Mesothelioma is a highly-aggressive cancer and the treatment can be challenging. A multidisciplinary approach with a team of healthcare specialists and experts from various medical fields may be necessary to treat the cancer at a healthcare institution that has the experience and expertise in dealing with such high-grade cancers.

The treatment for Well-Differentiated Papillary Mesothelioma may consist of the following measures:

• Surgery: A complete excision and removal of the tumor is typically undertaken
• Radiation therapy and/or chemotherapy is not generally required
• Immunotherapy: It is a newer method of treatment that has shown promising results in some individuals. The healthcare provider will determine if immunotherapy is to be employed in treating the tumor
• Embolization (clotting the vessels in the tumor) may be used to provide temporary relief from the symptoms and reduce blood loss during a surgical procedure
• Follow-up care with regular screening and check-ups are important

How can Well-Differentiated Papillary Mesothelioma be Prevented?

Current medical research has not established a method of preventing the formation of Well-Differentiated Papillary Mesothelioma. However, the following factors may be considered to reduce the risk of cancer development:

• Avoid or stop smoking: Individuals, who are smokers or have a prior history of the condition or suffer from other lung diseases, should regularly follow-up with their primary care physician to ensure that their lung functions are normal
• It is recommended that regular screening be undertaken for mesothelioma, if any of the following tumors are observed:
  • Clear cell renal cell carcinoma
  • Intrahepatic cholangiocarcinoma (a type of liver cancer)
  • Cutaneous melanoma
  • Uveal or ocular melanoma
• Regular medical screening at periodic intervals with blood tests, scans, and physical examinations are mandatory for those who have already been treated for this tumor

What is the Prognosis of Well-Differentiated Papillary Mesothelioma? (Outcomes/Resolutions)

• The prognosis of Well-Differentiated Papillary Mesothelioma is generally excellent with adequate treatment (complete surgical removal of the tumor) and long-term follow-up and regular screening for cancer, since it is a predominantly benign tumor
• However, in case of a malignant transformation of WDPM, due to a delay in diagnosis/treatment, the prognosis of the tumor will depend upon a set of several factors including the age and health status of the individual, the severity of the signs and symptoms, and the stage of the tumor

Additional and Relevant Useful Information for Well-Differentiated Papillary Mesothelioma:

Malignant epithelial mesothelioma is the most common histological type of malignant mesothelioma. It can occur in all 5 body sites, though the most frequent location is the pleura (in the lungs).