Malignant triton tumor (MTT) is a relatively rare, aggressive tumor made up of both malignant schwannoma

Schwannoma

A schwannoma is a benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves....

 cells and malignant rhabdomyoblasts. It's classified as a malignant peripheral nerve sheath tumor

Malignant peripheral nerve sheath tumor

A malignant peripheral nerve sheath tumor is a form of cancer of the connective tissue surrounding nerves. Given its origin and behavior it is classified as a sarcoma...

 with rhabdomyosarcoma

Rhabdomyosarcoma

A rhabdomyosarcoma is a type of cancer, specifically a sarcoma , in which the cancer cells are thought to arise from skeletal muscle progenitors. It can also be found attached to muscle tissue, wrapped around intestines, or in any anatomic location...

tous differentiation.

The unusual name "triton" was first used in reference to observation of supernumerary limbs containing bone

Bone

Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

 and muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 growing the backs of tritons after the implantation of the sciatic nerve

Sciatic nerve

The sciatic nerve is a large nerve fiber in humans and other animals. It begins in the lower back and runs through the buttock and down the lower limb...

 into the soft tissues of the back.

Criteria

There are three diagnostic criteria proposed:

1. the tumor arises along a peripheral nerve, or in a ganglioneuroma
   Ganglioneuroma
   Ganglioneuroma is a tumor of the sympathetic nerve fibers arising from neural crest cells.For example, it can be found also in the eye , or in the medulla of adrenal glands. Some may be a progressive form of a neuroblastoma....
   
   , or in a patient with neurofibromatosis type 1 (NF1), or has a metastatic
   Metastasis
   Metastasis, or metastatic disease , is the spread of a disease from one organ or part to another non-adjacent organ or part. It was previously thought that only malignant tumor cells and infections have the capacity to metastasize; however, this is being reconsidered due to new research...
   
    character
2. the growth characteristics of the tumor is typical for a Schwann cell tumor
   Schwannoma
   A schwannoma is a benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves....
   
   
3. rhabdomyoblasts arise within the body of the tumor.