Where Does Papillary Mesothelioma Develop?

The majority of well-differentiated papillary mesothelioma (WDPM) tumors develop in women. It develops in the abdominal cavity.

Doctors have found WDPMT tumor growth on several of the body’s protective membranes. This includes the pleura (lining of the lungs), pericardium (heart sac) and tunica vaginalis (lining of the testes).

Is WDPMT Cancerous?

From a medical standpoint, these tumors are benign. Some cases have turned into malignant mesothelioma over time. The chance of this happening is unlikely. Some people with WDPMT have also experienced several recurrences after treatment.

well-differentiated papillary mesothelioma
Well-differentiated papillary mesothelioma.

Solid papillary mesothelioma tumors are benign or very low-grade tumors. Separation from malignant mesotheliomas is important. A 2021 research report in Modern Pathology reported this stance.

Is There an Asbestos Connection?

Researchers are unsure if asbestos exposure causes this tumor. Some patients have a history of asbestos exposure, but most do not. The cause of this disease remains.

About 50 cases of WDPMT in the peritoneum exist in the medical literature. A 2019 study published in Annals of Surgical Oncology reported this data. There are also several small case reports of WDPM of the pleura. About 20 documented cases of testicular papillary mesothelioma exist.

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Symptoms and Characteristics

Many cases of well-differentiated papillary mesothelioma tumor have no symptoms. The disease causes pain and excessive fluid buildup in some patients.

Primary Characteristics of WDPMT

  • Well-differentiated tumors are low grade. This means their cancer cells resemble healthy cells and grow and multiply at a slow rate.
  • The cancer does not invade nearby tissues or spread throughout the body.
  • WDPMT is completely inactive in some cases, showing no signs of cell division.
  • The tumor’s cells feature small, finger-like projections called papillae.
  • Papillae sometimes create round swirls of calcium known as psammoma bodies.
  • Tumors form white or grey nodules ranging from less than 1 centimeter in size to more than 3 centimeters.
  • WDPMT can develop as a solitary mass or arise in many sites. The latter has more aggressive behavior.
  • Tumors are smaller than 1 centimeter in more than half of all cases.

WDPMT of the tunica vaginalis can cause scrotal swelling or the formation of testicular lumps. In one study of 22 WDPMT cases, only two patients reported to their doctors with symptoms. One patient experienced acute abdominal pain, and the other had chronic pelvic pain.

Misdiagnosis and Challenges

Doctors must collect a comprehensive tumor sample to prevent misdiagnosis. The only definitive procedure for diagnosing WDPM and other mesotheliomas is a biopsy. A biopsy collects a tissue sample for laboratory analysis.

Doctors may confuse WDPMT with several other cancers and conditions:

  • Reactive mesothelial hyperplasia
  • Adenomatoid tumor
  • Peritoneal carcinomatosis
  • Tuberculous peritonitis
  • Serous papillary carcinoma of the ovary
  • Serous papillary carcinoma of the peritoneum

While looking for signs of mesothelioma, doctors also look for negative markers. These markers signal it is likely not mesothelioma and is another type of cancer. For example, mesothelioma patients rarely test positive for PAX8 protein. If it’s detected, this could signal kidney cancer, thyroid cancer and cancers of the female reproductive system.

Doctors usually discover this condition during an unrelated pelvic or abdominal surgery. An imaging test, such as a CT scan, may find it. But this technique isn’t sensitive enough to detect tumors smaller than 1 centimeter in size.

Papillary Mesothelioma Treatment

Doctors have yet to reach a consensus on the most effective course of treatment.

Therapy usually involves a combination of the main types of mesothelioma treatment. These include surgery, chemotherapy and radiation therapy. Treatment options also depend on where the papillary mesothelioma tumors form.

A combination of surgery and heated chemotherapy treats abdominal cases. In a 2019 study published in Annals of Surgical Oncology, 37 of the 56 patients received this combination.

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Prognosis and Survival Rate of Papillary Mesothelioma

The outlook is better than the prognosis of patients with most other mesothelioma cell types.

Median Survival for Well-Differentiated Papillary Mesothelioma Tumor
WDPMT of the Pleura WDPMT of the Peritoneum
6 years and 2 months 12 years
Source: American Journal of Surgical Pathology, 2004; Annals of Surgical Oncology, January 2019

Only 5% to 10% of malignant mesothelioma patients survive five years after diagnosis. Several patients with WDPMT have survived for decades.

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