The most common form of malignant mesothelioma arises from the pleura – the lining membrane that covers the lungs — and is usually due to asbestos exposure. But this disease also can emerge from other tissues, including the peritoneum, heart, testicles and, less frequently, the liver and the greater omentum, a fat tissue layer that provides support to the intestines and lower abdominal organs.
Now, for the first time, a study published in the journal Surgical Case Reports chronicles the case of co-existence of malignant mesothelioma (MM) of the liver and the greater omentum. The case study is titled “Multiple malignant epithelioid mesotheliomas of the liver and greater omentum: a case report and review of the literature.”
MM of the liver and of the greater omentum are extremely rare. MM of the liver can have its origin in the connective tissue that encapsulates the liver, called Glisson’s capsule. But little is known about these two types of MM, with only 12 and two cases, respectively, having been described in the literature. No study has ever reported co-existence of these malignancies.
Investigators from the Kagoshima Kouseiren Hospital and Kagoshima University, Japan, now have described for the first time the case of a patient with MM of the liver and greater omentum.
The 36-year-old woman presented a two-month history of abdominal and back pain. Upon physical examination, blood tests, and several imaging evaluations, the team identified a solid mass in the liver, along with a significantly increased metabolism — a sign of cancer cells — of the greater omentum tissue. The woman was indicated for surgical removal of the tumors.
Upon detailed analysis of the tumors, researchers found the woman had multiple low-grade malignant epithelioid mesothelioma.
MM can be classified as epithelioid, sarcomatoid, and biphasic, depending on the tumor structure and cell type involved. The epithelioid subtype is the most common.
It is well known that cancer cells have increased capacity to proliferate. Typically, 15 to 20 percent of MM cells are actively dividing within the tumor. But this patient’s tumors had less than half of that proliferative rate, which suggests a lessened capacity to grow and invade other tissues.
“The tumor was therefore diagnosed as a low-grade malignant tumor, and metastasis was considered unlikely, although a primary malignant omental mesothelioma is also a rare disease,” the researchers wrote.
Both tumors of the liver and of the greater omentum had similar expression of biomarkers and presented similar structures, suggesting they could have originated from the same tumor that eventually spread to a different organ.
But the researchers point out that the cancer cells had little proliferative activity, and they did not find cells with invasive properties, which is indicative of isolated tumors.
“We should diagnose the tumors as multiple mesotheliomas, although we are not able to deny a possibility of dissemination,” they concluded.