Plexiform angiomyxoid myofibroblastic tumor (PAMT), also called plexiform angiomyxoma, plexiform angiomyxoid tumor, or myxofibroma, is an extremely rare

benign Malignancy () is the tendency of a medical condition to become progressively worse; the term is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous benign tumor, ''benign'' tumor in that a malig ...

mesenchymal Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood, or bone. The interactions between mesenchyme and epithelium help to form nearly ever ...

myxoid

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

along the

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...

. Most of PAMTs occur in the gastric antral region, but they can be situated anywhere in the

stomach The stomach is a muscular, hollow organ in the upper gastrointestinal tract of Human, humans and many other animals, including several invertebrates. The Ancient Greek name for the stomach is ''gaster'' which is used as ''gastric'' in medical t ...

. There is one recorded case of PAMT located in

duodenum The duodenum is the first section of the small intestine in most vertebrates, including mammals, reptiles, and birds. In mammals, it may be the principal site for iron absorption. The duodenum precedes the jejunum and ileum and is the shortest p ...

Classification

PAMT was first described by Takahashi et al. in 2007. Estimated frequency of PAMT is less than 1/150 compared to that of

gastrointestinal stromal tumor Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. GISTs arise in the smooth muscle pacemaker interstitial cell of Cajal, or similar cells. They are defined as tumors whose behavior i ...

s (GISTs). The

prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...

is similar in both genders and can develop at any age (7–75 years). The size of tumor ranges from 1.9 to 15.0 cm and the mean value is 6.3 cm. PAMT is considered as a

benign tumor A benign tumor is a mass of Cell (biology), cells (tumor) that does not Cancer invasion, invade neighboring tissue or Metastasis, metastasize (spread throughout the body). Compared to Cancer, malignant (cancerous) tumors, benign tumors generally ...

, due to its histological features such as the presence of bland tumor cells, low

proliferation index Proliferation may refer to: Weapons *Nuclear proliferation, the spread of nuclear weapons, material, and technology *Chemical weapon proliferation, the spread of chemical weapons, material, and technology *Missile proliferation, the spread of lon ...

, low mitotic-rate, absence of

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who i ...

and

vascular invasion Lymphovascular invasion (LVI or lymphovascular space invasion) is the invasion of a cancer to the blood vessels and/or lymphatics. Terminology Lymph: A clear or white fluid that travels through vessels, moves within tissues and work to keep all t ...

and no recurrence. In one case there has been reported vascular invasion, thus possibility of

malignant transformation Malignant transformation is the process by which cells acquire the properties of cancer. This may occur as a primary process in normal tissue, or secondarily as ''malignant degeneration'' of a previously existing benign tumor. Causes There are ...

cannot be excluded. But the limited number of reported cases is insufficient to draw any conclusion. The true biological potential of PAMT remains unknown due to its infrequency.

Presentation

Most patients present certain symptoms including

anaemia Anemia (also spelt anaemia in British English) is a blood disorder in which the blood has a reduced ability to carry oxygen. This can be due to a lower than normal number of red blood cells, a reduction in the amount of hemoglobin availab ...

due to

hematemesis Hematemesis is the vomiting of blood. It can be confused with hemoptysis (coughing up blood) or epistaxis (nosebleed), which are more common. The source is generally the upper gastrointestinal tract, typically above the suspensory muscle of du ...

ulceration An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected Organ (biology), organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caus ...

gastric outlet obstruction Gastric outlet obstruction (GOO) is a medical condition where there is an obstruction at the level of the pylorus, which is the outlet of the stomach. Individuals with gastric outlet obstruction will often have recurrent vomiting of food that ha ...

, fistulating abscess formation, intermittent epigastric discomfort and

abdominal pain Abdominal pain, also known as a stomach ache, is a symptom associated with both non-serious and serious medical issues. Since the abdomen contains most of the body's vital organs, it can be an indicator of a wide variety of diseases. Given th ...

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat. Over 30 d ...

vomiting Vomiting (also known as emesis, puking and throwing up) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteritis, pre ...

weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat (adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other conn ...

, or could be

asymptomatic Asymptomatic (or clinically silent) is an adjective categorising the medical conditions (i.e., injuries or diseases) that patients carry but without experiencing their symptoms, despite an explicit diagnosis (e.g., a positive medical test). P ...

with incidental finding.

Diagnosis

Accurate diagnosis of early PAMT is difficult, but there are certain morphological and immunophenotypic features enabling differentiation of this tumor from GIST or other mesenchymal gastric tumors. The diagnosis of submucosal tumors is performed by endoscopic ultrasonography (EUS), whereas the tumor phenotype and the tumor cell type can be evaluated by EUS-guided fine needle aspiration and

immunohistochemical Immunohistochemistry is a form of immunostaining. It involves the process of selectively identifying antigens in cells and tissue, by exploiting the principle of antibodies binding specifically to antigens in biological tissues. Albert Hewett ...

analysis. Immunohistochemically, the tumour cells show positive

staining Staining is a technique used to enhance contrast in samples, generally at the Microscope, microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissue (biology), tissues), in cytology (microscopic ...

for

vimentin Vimentin is a structural protein that in humans is encoded by the ''VIM'' gene. Its name comes from the Latin ''vimentum'' which refers to an array of flexible rods. Vimentin is a Intermediate filament#Type III, type III intermediate filamen ...

and smooth muscle actin (SMA). Focal

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. ...

positivity may be present. The tumour cells are generally negative for

CD117 Proto-oncogene c-KIT is the gene encoding the receptor tyrosine kinase protein known as tyrosine-protein kinase KIT, CD117 ( cluster of differentiation 117) or mast/stem cell growth factor receptor (SCFR). Multiple transcript variants encoding d ...

, DOG1, SMA,

Caldesmon Caldesmon is a protein that in humans is encoded by the ''CALD1'' gene. Caldesmon is a calmodulin binding protein. Like calponin, caldesmon tonically inhibits the ATPase activity of myosin in smooth muscle. This gene encodes a calmodulin- and ...

CD34 CD34 is a transmembrane phosphoglycoprotein protein encoded by the CD34 gene in humans, mice, rats and other species. CD34 derives its name from the cluster of differentiation protocol that identifies cell surface antigens. CD34 was first desc ...

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 ...

(EMA),

Cytokeratin Cytokeratins are keratin proteins found in the intracytoplasmic cytoskeleton of epithelial tissue. They are an important component of intermediate filaments, which help cells resist mechanical stress. Expression of these cytokeratins within ep ...

Anaplastic lymphoma kinase Anaplastic lymphoma kinase (ALK) also known as ALK tyrosine kinase receptor or CD246 (cluster of differentiation 246) is an enzyme that in humans is encoded by the ''ALK'' gene. Identification Anaplastic lymphoma kinase (ALK) was originally di ...

(ALK). Focal

CD10 Neprilysin (; also known as membrane metallo-endopeptidase (MME), neutral endopeptidase (NEP), cluster of differentiation 10 (CD10) and common acute lymphoblastic leukemia antigen (CALLA)) is an enzyme that in humans is encoded by the ''MME'' ge ...

positivity can be observed. The pattern of positivity indicates the myofibroblastic nature of the tumour cells.

Pathological features

Macroscopically, the tumour manifests as elevated or polypoidal mass lesion most commonly affecting the antral region of the stomach, however, in some cases

fundus ''Fundus'' (Latin for "bottom") is an anatomical term referring to that part of a concavity in any organ, which is at the far end from its opening. It may refer to: Anatomy * Fundus (brain), the deepest part of any sulcus of the cerebral cortex * F ...

and body of the stomach as well as

esophagus The esophagus (American English), oesophagus (British English), or œsophagus (Œ, archaic spelling) (American and British English spelling differences#ae and oe, see spelling difference) all ; : ((o)e)(œ)sophagi or ((o)e)(œ)sophaguses), c ...

might be involved.

Duodenal bulb The duodenal bulb (also ampulla of duodenum, duodenal ampulla, or duodenal cap) is the initial, dilated portion of (the superior part of) the duodenum just distal to the stomach; it begins at the pylorus and ends at the neck of the gallbladder. ...

or the

pylorus The pylorus ( or ) connects the stomach to the duodenum. The pylorus is considered as having two parts, the ''pyloric antrum'' (opening to the body of the stomach) and the ''pyloric canal'' (opening to the duodenum). The ''pyloric canal'' ends a ...

are involved roughly in 33% cases. Microscopically, the gastric wall shows a characteristic multinodular plexiform pattern of the tumour. The uppermost layer of

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

is in many cases ulcerated. The fascicular arrangement of the tumour can be observed focally. The tumour cells are entrenched in a highly vasculated myxoid background. The vessels are thin arborizing with or without

thrombi A thrombus ( thrombi) is a solid or semisolid aggregate from constituents of the blood (platelets, fibrin, red blood cells, white blood cells) within the circulatory system during life. A blood clot is the final product of the blood coagulatio ...

. The individual tumour cells are spindle to ovoid shaped, with indistinct cell borders, bland nuclear

chromatin Chromatin is a complex of DNA and protein found in eukaryote, eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important r ...

, inconspicuous

nucleoli The nucleolus (; : nucleoli ) is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis. The nucleolus also participates in the formation of signal recognition particles and plays a ro ...

, and scant eosinophilic

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

. Mitotic rate is low. Stromal collagenisation is inconspicuous. The myxoid background stroma stain positive for

Alcian blue Alcian blue () is any member of a family of polyvalent basic dyes, of which the Alcian blue 8G (also called Ingrain blue 1, and C.I. 74240, formerly called Alcian blue 8GX from the name of a batch of an ICI product) has been historically the mo ...

stain. Many

mast cell A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a p ...

s can be seen dispersed in the stroma.

Treatment

Currently, the treatment of choice for PAMTs is distal or partial

gastrectomy A gastrectomy is a partial or total surgical removal of the stomach. Indications Gastrectomies are performed to treat stomach cancer and perforations of the stomach wall. For severe duodenal ulcers, it may be necessary to remove the lower ...

. Further studies could provide more information about its histogenesis and molecular signature that could be applied in targeted therapeutic approach.

Prognosis

PAMT has a seemingly good prognosis without reported relapse or

metastasis Metastasis is a pathogenic agent's spreading from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, ...

. Due to tumors small size and a good prognosis it is possible to remove this tumor by

endoscopic submucosal dissection Endoscopic submucosal dissection (ESD) is an advanced surgical procedure using endoscopy to remove gastrointestinal tumors that have not entered the muscle layer. ESD may be done in the esophagus, stomach or colon. Application of endoscopic rese ...

(ESD) under

gastroscopy Esophagogastroduodenoscopy (EGD) or oesophagogastroduodenoscopy (OGD), also called by various other names, is a diagnostic endoscopic procedure that visualizes the upper part of the gastrointestinal tract down to the duodenum. It is considered ...

at an early stage.

References

{{Reflist Tumor