What Is Malignant Mesothelioma?
A layer of specialized cells called mesothelial cells lines the chest cavity, abdominal cavity, and the cavity
around your heart. These cells also cover the outer surface of most of your internal organs. The tissue formed by
these cells is called mesothelium.
The mesothelium helps protect your organs by producing a special lubricating fluid that allows organs to move
around. This fluid makes it easier for the lungs to move inside the chest during breathing. The mesothelium of
the chest is called the pleura and the mesothelium of the abdomen is known as the peritoneum.The
mesothelium of the "sac-like" space around the heart (pericardial cavity) is called the pericardium.
Tumors of the mesothelium can be noncancerous (benign) or cancerous (malignant). A malignant tumor of the
mesothelium is called a malignant mesothelioma,however, malignant mesothelioma is often simply called
mesothelioma.
It is important not to confuse malignant mesothelioma with benign tumors that also start in the mesothelium.
The mesothelium of certain female and male reproductive organs may develop a type of benign tumor called an
adenomatoid tumor. In men, this noncancerous tumor often starts in the epididymis (a small collection of
ducts that carry sperm cells out of the testicle). In women, this tumor may begin in the fallopian tubes (tubes
that carry eggs from the ovaries to the uterus or womb). Another noncancerous tumor that may begin in
mesothelium near female reproductive organs is called benign cystic mesothelioma.
A type of benign tumor that used to be called benign fibrous mesothelioma can form in the pleura surrounding
the lungs. Doctors now know that this tumor actually starts from tissue under the mesothelium and not from
mesothelial cells. For this reason, the new name of this tumor is solitary fibrous tumor of the pleura. This
disease is usually not cancerous, but cancerous forms can occur. A similar disease starting in the peritoneum is
called solitary fibrous tumor of the peritoneum. The tumors described in this paragraph are usually removed
by surgery, and there is no need for additional treatment. Only malignant mesothelioma will be discussed
further in this document.
Malignant mesotheliomas are divided into 3 main types:
l epithelioid (50% to 70% are of this type) - this type has the best outlook for survival
(prognosis)
l sarcomatoid (7% to 20% are of this type)
l mixed/biphasic (20% to 35% are of this type)
Treatment options are the same for all 3 types.
About three-fourths of mesotheliomas start in the chest cavity. They are known as pleural mesotheliomas.
Another 10% to 20% begin in the abdomen. These are called peritoneal mesotheliomas. Pericardial
mesotheliomas start in the cavity around the heart and are very rare. The covering layer of the testicles is
actually an outpouching of peritoneum into the scrotum. Mesotheliomas that affect this covering of the testicles
can occur but are quite rare.
