A mastocytoma or mast cell tumor is a type of round-cell tumor consisting of

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. It is found in humans and many animal species; it also can refer to an accumulation or

nodule Nodule may refer to: * Nodule (geology), a small rock or mineral cluster * Manganese nodule, a metallic concretion found on the seafloor *Nodule (medicine), a small aggregation of cells *Root nodule Root nodules are found on the roots of plants, ...

of mast cells that resembles a tumor. Mast cells originate from the

bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...

and are normally found throughout the

connective tissue Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...

of the body as normal components of the

immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

. As they release

histamine Histamine is an organic nitrogenous compound involved in local immune responses communication, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Discovered in 19 ...

, they are associated with

allergic reaction Allergies, also known as allergic diseases, are various conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include Allergic rhinitis, hay fever, Food allergy, food al ...

s. Mast cells also respond to tissue trauma. Mast cell granules contain histamine,

heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Heparin is a blood anticoagulant that increases the activity of antithrombin. It is used in the treatment of myocardial infarction, ...

platelet-activating factor Platelet-activating factor, also known as PAF, PAF-acether or AGEPC (acetyl-glyceryl-ether-phosphorylcholine), is a potent phospholipid activator and mediator of many leukocyte functions, platelet aggregation and degranulation, inflammation, and an ...

, and other substances. Disseminated

mastocytosis Mastocytosis, a type of 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 ...

is rarely seen in young dogs and cats, while mast cell tumors are usually skin tumors in older dogs and cats. Although not always malignant, they do have the potential to be. Up to 25 percent of skin tumors in dogs are mast cell tumors, with a similar number in cats.

Signs and symptoms

Humans

When mastocytomas affect humans, they are typically found in skin. They usually occur as a single lesion on the trunk or wrist. Although it is rare, mastocytomas are sometimes found in the lung. It can also affect children.

Animals

Mast cell tumors are known among veterinary

oncologist Oncology is a branch of medicine that deals with the study, treatment, diagnosis, and prevention of cancer. A medical professional who practices oncology is an ''oncologist''. The name's etymological origin is the Greek word ὄγκος (''� ...

s as 'the great pretenders' because their appearance can be varied, from a

wart Warts are non-cancerous viral growths usually occurring on the hands and feet but which can also affect other locations, such as the genitals or face. One or many warts may appear. They are distinguished from cancerous tumors as they are caus ...

-like nodule to a soft subcutaneous lump (similar on palpation to a benign

lipoma A lipoma is a benign tumor made of adipose tissue, fat tissue. They are generally soft to the touch, movable, and painless. They usually occur just under the skin, but occasionally may be deeper. Most are less than in size. Common locations inc ...

) to an ulcerated skin mass. Most mast cell tumors are small, raised lumps on the skin. They may be hairless, ulcerated, or itchy. They are usually solitary, but in about six percent of cases, there are multiple mast cell tumors (especially in Boxers and Pugs). Manipulation of the tumor may result in redness and swelling from release of mast cell granules, also known as Darier's sign, and prolonged local hemorrhage. In rare cases, a highly malignant tumor is present, and signs may include loss of appetite,

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 ...

diarrhea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

, and

anemia 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 availabl ...

. The presence of these signs usually indicates

, which is the spread of mast cells throughout the body. Release of a large amount of histamine at one time can result in ulceration of 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 ...

and

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 ...

(present in up to 25 percent of cases) or

disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking Microvessel, small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems ...

. When

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, ...

does occur, it is usually to the

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

spleen The spleen (, from Ancient Greek '' σπλήν'', splḗn) is an organ (biology), organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The spleen plays important roles in reg ...

lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...

s and

. File:Mast cell tumor side.JPG, Mast cell tumor on the side of a dog File:Mast cell tumor inner thigh.JPG, Mast cell tumor on the inner thigh of a dog File:Mast cell tumor of the toe.JPG, Mast cell tumor of the paw

Diagnosis

needle aspiration biopsy Fine-needle aspiration (FNA) is a diagnostic procedure used to investigate lumps or masses. In this technique, a thin (23–25 gauge (0.52 to 0.64 mm outer diameter)), hollow needle is inserted into the mass for sampling of cells that, ...

of the tumor will typically show a large number of mast cells. This is sufficient to make the diagnosis of a mast cell tumor, although poorly differentiated mast cells may have few granules and thus are difficult to identify. The granules of the mast cell stain blue to dark purple with a

Romanowsky stain Romanowsky staining is a prototypical staining technique that was the forerunner of several distinct but similar stains widely used in hematology (the study of blood) and cytopathology (the study of diseased cells). Romanowsky-type stains are use ...

, and the cells are medium-sized. However, a surgical

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, an interventional radiologist, or an interventional cardiology, interventional cardiologist. The process involves the extraction of sampling (medicine), sample ...

is required to find the grade of the tumor. The grade depends on how well the mast cells are differentiated,

mitotic Mitosis () is a part of the cell cycle in eukaryotic cells in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis is an equational division which gives rise to genetically identical cells in which the t ...

activity, location within the skin, invasiveness, and the presence of

inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

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 ...

. *Grade I – well differentiated and mature cells with a low potential for metastasis *Grade II – intermediately differentiated cells with potential for local invasion and moderate metastatic behavior *Grade III – undifferentiated, immature cells with a high potential for metastasis However, there is a significant amount of discordance between veterinary pathologists in assigning grades to mast cell tumors due to imprecise criteria. The disease is also staged according to the

WHO The World Health Organization (WHO) is a specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Geneva, Switzerland, and has 6 regional offices and 15 ...

system: *Stage I - a single skin tumor with no spread to

s *Stage II - a single skin tumor with spread to lymph nodes in the surrounding area *Stage III - multiple skin tumors or a large tumor invading deep to the skin with or without lymph node involvement *Stage IV – a tumor with metastasis to the spleen, liver, or bone marrow, or with the presence of mast cells in the blood

X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

ultrasound Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...

, or lymph node, bone marrow, or organ biopsies may be necessary to stage the disease.

Treatment and prognosis

Removal of the mast cell tumor through surgery is the treatment of choice.

Antihistamine Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides ...

s, such as

diphenhydramine Diphenhydramine, sold under the brand name Benadryl among others, is an antihistamine and sedative. Although generally considered sedating, diphenhydramine can cause paradoxical central nervous system stimulation in some individuals, particula ...

, are given prior to surgery to protect against the effects of histamine released from the tumor. Wide margins (two to three centimeters) are required because of the tendency for the tumor cells to be spread out around the tumor. If complete removal is not possible due to the size or location, additional treatment, such as

radiation therapy Radiation therapy or radiotherapy (RT, RTx, or XRT) is a therapy, treatment using ionizing radiation, generally provided as part of treatment of cancer, cancer therapy to either kill or control the growth of malignancy, malignant cell (biology), ...

chemotherapy Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy re ...

, may be necessary.

Prednisone Prednisone is a glucocorticoid medication mostly used to immunosuppressive drug, suppress the immune system and decrease inflammation in conditions such as asthma, COPD, and rheumatologic diseases. It is also used to treat high blood calcium ...

is often used to shrink the remaining tumor portion.

H2 blocker H2 antagonists, sometimes referred to as H2RAs and also called H2 blockers, are a class of medications that block the action of histamine at the histamine H2 receptors of the parietal cells in the stomach. This decreases the production of stoma ...

s, such as

cimetidine Cimetidine, sold under the brand name Tagamet among others, is a histamine H2 receptor antagonist that inhibits stomach acid production. It is mainly used in the treatment of heartburn and peptic ulcers. With the development of proton pump ...

, protect against stomach damage from histamine.

Vinblastine Vinblastine, sold under the brand name Velban among others, is a chemotherapy medication, typically used with other medications, to treat a number of types of cancer. This includes Hodgkin's lymphoma, non-small-cell lung cancer, bladder canc ...

and lomustine are common chemotherapy agents used to treat mast cell tumors. Toceranib and

masitinib Masitinib is a tyrosine-kinase inhibitor used in the treatment of mast cell tumours in animals, specifically dogs.Information abouMasivet at the European pharmacy agency website Since its introduction in November 2008 it has been distributed ...

, examples of

receptor tyrosine kinase Receptor tyrosine kinases (RTKs) are the high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 58 encode receptor tyrosine kinas ...

inhibitors, are used in the treatment of canine

tumors. Both were recently approved by the

U.S. Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

(FDA) as dog-specific anti

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

drugs. Grade I or II mast cell tumors that can be completely removed have a good

prognosis Prognosis ( Greek: πρόγνωσις "fore-knowing, foreseeing"; : prognoses) is a medical term for predicting the likelihood or expected development of a disease, including whether the signs and symptoms will improve or worsen (and how quickly) ...

. One study showed about 23 percent of incompletely removed grade II tumors recurred locally. Any mast cell tumor found in 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 ...

, paw, or on the muzzle has a guarded prognosis. Previous beliefs that tumors in the groin or

perineum The perineum (: perineums or perinea) in placentalia, placental mammals is the space between the anus and the genitals. The human perineum is between the anus and scrotum in the male or between the anus and vulva in the female. The perineum is ...

carried a worse prognosis have been discounted. Tumors that have spread to the lymph nodes or other parts of the body have a poor prognosis. Any dog showing symptoms of mastocytosis or with a grade III tumor has a poor prognosis. Dogs of the Boxer breed have a better than average prognosis because of the relatively benign behavior of their mast cell tumors. Multiple tumors that are treated similarly to solitary tumors do not seem to have a worse prognosis. Mast cell tumors do not necessarily follow the histological prognosis. Further prognostic information can be provided by AgNOR stain of histological or cytological specimen. Even then, there is a risk of unpredictable behavior.

Other animals

Mast cell tumors are an uncommon occurrence in

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...

s. They usually occur as benign, solitary masses on the skin of the head, neck, trunk, and legs. Mineralization of the tumor is common. In

pig The pig (''Sus domesticus''), also called swine (: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the genus '' Sus''. Some authorities cons ...

s and

cattle Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are calle ...

, mast cell tumors are rare. They tend to be solitary and benign in pigs and multiple and malignant in cattle. Mast cell tumors are found in the skin of cattle most commonly, but these may be metastases from tumors of the

viscera In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to a ...

. Other sites in cattle include the spleen, muscle, gastrointestinal tract, omentum, and uterus.

Dogs

Mast cell tumors mainly occur in older adult dogs, but have been known to occur on rare occasions in puppies. The following breeds are commonly affected by mast cell tumors: * Boxer *

Staffordshire bull terrier The Staffordshire Bull Terrier, also called the Staffy or Stafford, is a purebred dog of small to medium size in the terrier group that originated in the northern parts of Birmingham and in the Black Country of Staffordshire, for which it ...

Bulldog The Bulldog is a British breed of dog of mastiff type. It may also be known as the English Bulldog or British Bulldog. It is a stocky, muscular dog of medium size, with a large head, thick folds of skin around the face and shoulders and a rel ...

Basset hound The Basset Hound is a short-legged breed of scent hound. The Basset Hound was developed in Great Britain from several now-extinct strains of France, French basset breeds. It was bred primarily for hunting rabbit and hare on foot, moving slowly en ...

Weimaraner The is a German breed of hunting dog of medium to large size, with history going back at least to the nineteenth century. It originated in the area of the city of Weimar (then in Saxe-Weimar-Eisenach, now in the state of Thuringia), for which ...

Boston terrier The Boston Terrier is a breed of dog originating in the United States of America. This "American Gentleman" was accepted in 1893 by the American Kennel Club as a non-sporting breed. Boston Terriers are small and compact with a short tail and ere ...

Great Dane The Great Dane is a German list of dog breeds, breed of large mastiff-sighthound, which descends from hunting dogs of the Middle Ages used to hunt bears, wild boar, and deer. They were also used as guardian dogs of German nobility. It is one o ...

* Golden retriever *

Labrador retriever The Labrador Retriever or simply Labrador or Lab is a British list of dog breeds, breed of water dog retriever gun dog. It was developed in the United Kingdom from St. John's water dogs imported from the Newfoundland Colony, colony of Newfoun ...

Beagle The Beagle is a small breed of scent hound, similar in appearance to the much larger foxhound. The beagle was developed primarily for hunting rabbit or hare, known as beagling. Possessing a great sense of smell and superior tracking inst ...

German shorthaired pointer The German Shorthaired Pointer or is a German breed of continental pointing dog of Braque type. It originated in the nineteenth century in what is now Germany. It is of medium size, and is an all-purpose gun dog suitable for hunting and retrie ...

Scottish terrier The Scottish Terrier (; also known as the Aberdeen Terrier), popularly called the Scottie, is a dog breed, breed of dog. Initially one of the highland breeds of terrier that were grouped under the name of ''Skye Terrier'', it is one of five br ...

Pug The Pug is a breed of dog with the physically distinctive features of a wrinkly, short-muzzled face, and curled tail. An ancient breed, with roots dating back to 400 B.C., they have a fine, glossy coat that comes in a variety of colors, most ...

Shar pei The Shar Pei () is a dog breed from southern China. Traditionally kept as a property guardian, the shar pei was driven to the brink of extinction in the 20th century. The breed is known in the West for its deep wrinkles, while a traditional less ...

* Rhodesian ridgeback

Cats

Two types of mast cell tumors have been identified in cats, a mast cell type similar to dogs and a histiocytic type that appears as subcutaneous nodules and may resolve spontaneously. Young

Siamese cat The Siamese cat (; แมวสยาม, Maeo Sayam; แมววิเชียรมาศ, Maeo Wichien Maat) is one of the first distinctly recognised breeds of Asian cat. It derives from the Wichianmat landrace. The Siamese cat is one ...

s are at an increased risk for the histiocytic type, although the mast cell type is the most common in all cats and is considered to be benign when confined to the skin. Mast cell tumors of the skin are usually located on the head or trunk. Gastrointestinal and splenic involvement is more common in cats than in dogs; 50 percent of cases in dogs primarily involved the spleen or intestines. Gastrointestinal mast cell tumors are most commonly found in the muscularis layer of the

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

, but can also be found in the

large intestine The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the Digestion, digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces befor ...

. It is the third most common intestinal tumor in cats, after

lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). The name typically refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlarged lymph node ...

and

adenocarcinoma Adenocarcinoma (; plural adenocarcinomas or adenocarcinomata ; AC) is a type of cancerous tumor that can occur in several parts of the body. It is defined as neoplasia of epithelial tissue that has glandular origin, glandular characteristics, or ...

. Diagnosis and treatment are similar to that of the dog. Cases involving difficult to remove or multiple tumors have responded well to

strontium-90 Strontium-90 () is a radioactive isotope of strontium produced by nuclear fission, with a half-life of 28.79 years. It undergoes β− decay into yttrium-90, with a decay energy of 0.546 MeV. Strontium-90 has applications in medicine a ...

radiotherapy Radiation therapy or radiotherapy (RT, RTx, or XRT) is a treatment using ionizing radiation, generally provided as part of cancer therapy to either kill or control the growth of malignant cells. It is normally delivered by a linear particle ...

as an alternative to surgery. The prognosis for solitary skin tumors is good, but guarded for tumors in other organs. Histological grading of tumors has little bearing on prognosis.

References

External links

''Mast Cell Tumors'' from The Pet Health Library
{{Soft tissue tumors and sarcomas Dog diseases Cat diseases Horse diseases Swine diseases Bovine diseases