Ectomesenchymal chondromyxoid tumor (ECT) is a benign

intraoral In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on t ...

tumor with presumed origin from undifferentiated (ecto)mesenchymal cells. There are some who think it is a myoepithelial tumor type.

Controversies about origin

* Derived from

ectomesenchymal Ectomesenchyme has properties similar to mesenchyme. The origin of the ectomesenchyme is disputed. It is either like the mesenchyme, arising from mesodermic cells, or conversely arising from neural crest cells. The neural crest is a critical group ...

cells migrating from

neural crest Neural crest cells are a temporary group of cells unique to vertebrates that arise from the embryonic ectoderm germ layer, and in turn give rise to a diverse cell lineage—including melanocytes, craniofacial cartilage and bone, smooth muscle, per ...

(there is immunophenotypic support for this theory). * Equivalent to soft tissue

myoepithelioma Myoepithelioma of the head and neck, also myoepithelioma, is a salivary gland tumour of the head and neck that is usually benign. When malignant, which is exceedingly rare, they are known as malignant myoepithelioma or Myoepithelial carcinoma, and ...

. There is morphologic and immunohisthochemical support for this theory, with some authors advocating interchangeable terms.

Signs and Symptoms

Patients present with a painless, slow-growing mass usually within the tongue (most commonly the anterior dorsal tongue). There is an intact surface epithelium.

Management

* Surgical excision is the treatment of choice, with recurrences only when there is incomplete excision.

Pathology findings

Macroscopic

* Submucosal circumscribed but not encapsulated nodular mass, often with entrapped muscle bundles at the edge. It may have a

gelatinous Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...

appearance. Most tumors are small, up to 2 cm (given the confines of the tongue, a larger mass would cause significant clinical problems).

Microscopic Pathology

* Submucosal unencapsulated but well-delineated or circumscribed nodule, often separated from the periphery and internally by

fibrous connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tissue is ...

bands. The cells are arranged in cords, nests, and net-like sheets. The cells may extend into and entrap soft tissue structures including skeletal muscle and nerve bundles. * The tumor is made up of small round, oval, spindle, or stellate cells that have a very monotonous appearance. There are small dark nuclei with variably amounts of light to basophilic

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...

. * Nuclear

pleomorphism Pleomorphism may refer to: * Pleomorphism (cytology), variability in the size and shape of cells and/or their nuclei * Pleomorphism (microbiology), the ability of some bacteria to alter their shape or size in response to environmental conditions ...

, multinucleation, and mitotic figures are usually not seen. Atypical mitoses and necrosis is absent. * There is a background stroma composed of chondromyxoid to myxoid material. Sometimes large cells are seen in chondroid or

cartilaginous Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck a ...

areas. Swirling formations give the appearance of neural tissue. * Importantly, there is an absence of

glands In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...

or myoepithelial components.

Immunohistochemistry

* Positive: Glial fibrillary acidic protein ( GFAP), pancytokeratin, and

S100 protein The S100 proteins are a family of low molecular-weight proteins found in vertebrates characterized by two calcium-binding sites that have helix-loop-helix (" EF-hand-type") conformation. At least 21 different S100 proteins are known. They are en ...

. Smooth muscle actin may be positive in about 50% of cases. * Negative:

Epithelial membrane antigen Mucin short variant S1, also called polymorphic epithelial mucin (PEM) or epithelial membrane antigen (EMA), is a mucin encoded by the ''MUC1'' gene in humans. Mucin short variant S1 is a glycoprotein with extensive O-linked glycosylation of its e ...

desmin Desmin is a protein that in humans is encoded by the ''DES'' gene. Desmin is a muscle-specific, type III intermediate filament that integrates the sarcolemma, Z disk, and nuclear membrane in sarcomeres and regulates sarcomere architecture. Str ...

, p63 and

calponin Calponin is a calcium binding protein. Calponin tonically inhibits the ATPase activity of myosin in smooth muscle. Phosphorylation of calponin by a protein kinase, which is dependent upon calcium binding to calmodulin, releases the calponin's ...

Ancillary Studies

* Alcian blue will give a blue staining to the stromal matrix material. *

Mucicarmine Mucicarmine stain is a staining procedure used for different purposes. In microbiology the stain aids in the identification of a variety of microorganisms based on whether or not the cell wall stains intensely red. Generally this is limited to micro ...

will also highlight the stromal matrix (pink). * There is a specific recurrent ''RREB1-MKL2'' gene fusion present in these tumors.

Differential diagnoses

The tumor is quite unique, but other tumors are considered in the differential diagnosis histologically. They included pleomorphic adenoma,

, myxoid

neurofibroma A neurofibroma is a benign nerve-sheath tumor in the peripheral nervous system. In 90% of cases, they are found as stand-alone tumors (solitary neurofibroma, solitary nerve sheath tumor or sporadic neurofibroma), while the remainder are found in p ...

, neurothekeoma (nerve sheath myxoma), chondroid choristoma, extraskeletal myxoid chondrosarcoma, focal oral mucinosis, and an ossifying fibromyxoid tumor of soft parts.

Epidemiology

Exceedingly rare, this tumor develops in a wide age range, although often in young patients without a sex predilection. The vast majority develop within the anterior dorsal tongue, with palate and base of tongue rarely affected.