Papillary mesothelioma is a rare subtype of epithelioid mesothelioma, seen more commonly in peritoneal types.
Papillary mesothelioma, also referred to as well-differentiated papillary mesothelioma (WDPM), isn’t definitively correlated to asbestos exposure like other forms of malignant mesothelioma, though some cases have shown a potential connection. Other risk factors have been identified, such as a past of endometriosis, surgery or pelvic inflammatory disease. This form can affect both men and women of all ages, but the majority of cases have been seen in young women of reproductive age. Most papillary mesothelioma tumors are benign and can be surgically removed. Studies have demonstrated a generally positive prognosis, with some patients surviving 20 years or longer.
Papillary Cell Structure
Papillary mesothelioma is most commonly found in the peritoneum (abdominal linings), though tumors have been seen in the pleura (lung linings) and tunica vaginalis (testicular linings) in some cases. Papillary tumors are recognized by their epithelial cell type and microscopic growth patterns, with finger-like projections (papillae) lined with single layers of flat mesothelial cells. The slow growth patterns of epithelial cells help differentiate them from sarcomatoid mesothelioma, cells that exhibit aggressive behavior and rapid growth. Identifying tumor cell structure can help differentiate WDPM from other common misdiagnoses, including:
- Reactive mesothelial hyperplasia
- Peritoneal carcinomatosis
- Peritoneal mesothelioma
- Peritoneal serous papillary carcinoma
- Papillary endosalpingiosis
- Adenomatoid tumors
- Malignant vascular tumors of the serous membranes
- Tuberculous peritonitis
Diagnosing Papillary Mesothelioma
Papillary mesothelioma generally has low malignant potential, but an early diagnosis is still important to ensure the best prognosis for the patient.
The majority of patients diagnosed with papillary mesothelioma have shown no symptoms. In a recent study involving 26 female cases, only two patients presented symptoms. Despite the disease’s asymptomatic nature, the symptoms that have been reported can help physicians reach an accurate diagnosis.
- Abdominal pain
- Chronic pelvic pain
- Shortness of breath
- Swelling of the lower extremities
In addition to observing a patient’s symptoms, physicians will also look at their medical history for potential risk factors of WDPM, like a history of endometriosis, pelvic inflammatory disease or previous surgeries. In the same study of 26 diagnosed women, six had endometriosis and 10 had recently undergone surgery. No patients in this case report had a history of asbestos exposure.
The asymptomatic nature of well-differentiated papillary mesothelioma often leads to the incidental finding of mesothelioma during testing or surgeries for other conditions. If an abnormality is found or if symptoms are presented, physicians will conduct image testing. X-rays, CT scans, MRIs and PET scans can be used to identify tumor location, sizing and progression. Many mesothelioma specialists feel that the presence of psammoma bodies can also help differentiate papillary mesothelioma from other diseases. However, a biopsy is performed to definitively diagnose mesothelioma.
A biopsy collects a tissue sample for specialists to analyze cell structure through a process known as histology. Such testing will determine if a tumor is malignant or benign, determine mesothelioma type and identify staging. Biopsies are crucial for a differential diagnosis and preventing cancer misdiagnosis.
Papillary Mesothelioma Prognosis
Well-differentiated papillary mesothelioma has so few reported cases that researchers have been unable to identify a clear path of progression and average life expectancy. Some cases have been benign and cured with surgical resection, resulting in long-term survival. From the study of 26 patients, 22 lived with no recurrence, while one patient experienced recurrence of WDPM after four years and three patients died of other causes.
All benign forms of mesothelioma can potentially recur with malignancy. With uncertain malignant potential of recurrent tumors, long-term follow ups and monitoring are necessary. If WDPM tumors recur with malignancy, prognosis is much worse. One study of 24 rare papillary cases noted life expectancies ranging from 36 months to 180 months, with a 74-month average survival.
Treatment Options for Papillary Mesothelioma
Treatment for well-differentiated papillary mesothelioma depends on malignancy. Benign mesothelioma tumors are typically removed with complete surgical resection. Malignant mesothelioma, however, requires more aggressive treatments, like a multimodal plan consisting of surgery in combination with chemotherapy or radiation.
One study looked at the use of surgical debulking and hyperthermic intraperitoneal chemotherapy (HIPEC) in treating malignant papillary mesothelioma and found the 5-year progression-free survival rate was 79.7%, while progression-free survival with just surgery was only two years on average. This study suggests that when treating malignant WDPM, the use of aggressive treatments like chemotherapy can help reduce the chances of recurrence and improve the prognosis for patients.
Other mesothelioma specialists feel that chemotherapy and radiation should not be used unless necessary, as they could cause avoidable damage to healthy organs and tissues. Ultimately, more research is needed to establish a standard treatment plan for papillary mesothelioma, and mesothelioma patients should seek professional medical advice to establish an individualized treatment plan.
Author: Linda Molinari
Editor in Chief, Mesothelioma Cancer AllianceRead about Linda
Reviewer: Dr. James Stevenson
Medical Reviewer and Thoracic Medical OncologistRead about Dr. Stevenson
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