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 par ...

s. It is found in humans and many animal species; it also can refer to an accumulation or nodule of mast cells that resembles a tumor. Mast cells originate from the

bone marrow Bone marrow is a semi-solid tissue found within the 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 is composed of hematopoietic ce ...

and are normally found throughout the

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 tiss ...

of the body as normal components of the

immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...

. As they release

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

, they are associated with

allergic reaction Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derma ...

s. Mast cells also respond to tissue

trauma Trauma most often refers to: * Major trauma, in physical medicine, severe physical injury caused by an external source * Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic i ...

. Mast cell granules contain histamine,

heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the treatm ...

, platelet-activating factor, and other substances. Disseminated

mastocytosis Mastocytosis, a type of mast cell disease, is a rare disorder affecting both children and adults caused by the accumulation of functionally defective mast cells (also called ''mastocytes'') and CD34+ mast cell precursors. People affected by mas ...

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.

Other 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 (''ó ...

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

wart Warts are typically small, rough, hard growths that are similar in color to the rest of the skin. They typically do not result in other symptoms, except when on the bottom of the feet, where they may be painful. While they usually occur on the ...

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

lipoma A lipoma is a benign tumor made of 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 include upper back, ...

) to an

ulcerated An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughing o ...

skin mass. Most mast cell tumors are small, raised lumps on the skin. They may be hairless,

, 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 Darier's sign is a change observed after stroking lesions on the skin of a person with systemic mastocytosis or urticaria pigmentosa. In general, the skin becomes swollen, itchy and red. This is a result of compression of mast cells, which a ...

, 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 and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the Human nose, nose. Vomiting can be the result of ailments like Food-poisoning, foo ...

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...

, and

anemia Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, th ...

. 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 gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

and

duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...

(present in up to 25 percent of cases) or disseminated intravascular coagulation. When

metastasis Metastasis is a pathogenic agent's spread 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, then, ...

does occur, it is usually to the

liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

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 inclu ...

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, aft ...

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, also known as Romanowsky–Giemsa 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 di ...

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

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a diseas ...

is required to find the

grade Grade most commonly refers to: * Grade (education), a measurement of a student's performance * Grade, the number of the year a student has reached in a given educational stage * Grade (slope), the steepness of a slope Grade or grading may also ref ...

of the tumor. The grade depends on how well the mast cells are differentiated,

mitotic In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintai ...

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

inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

. *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 pathologist Veterinary pathologists are veterinarians who specialize in the diagnosis of diseases through the examination of animal tissue and body fluids. Like medical pathology, veterinary pathology is divided into two branches, anatomical pathology an ...

s in assigning grades to mast cell tumors due to imprecise criteria. The disease is also staged according to the

WHO Who or WHO may refer to: * Who (pronoun), an interrogative or relative pronoun * Who?, one of the Five Ws in journalism * World Health Organization Arts and entertainment Fictional characters * Who, a creature in the Dr. Seuss book '' Horton He ...

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, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

ultrasound Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...

, 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 re ...

s, such as

diphenhydramine Diphenhydramine (DPH) is an antihistamine and sedative mainly used to treat allergies, insomnia, and symptoms of the common cold. It is also less commonly used for tremor in parkinsonism, and nausea. It is taken by mouth, injected into a vein ...

, 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, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...

chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherap ...

, 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 sto ...

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. The development of longer-acting H2 rec ...

, protect against stomach damage from histamine.

Vinblastine Vinblastine (VBL), 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 ca ...

and

lomustine Lomustine (INN); abbreviated as CCNU; original brand name CeeNU, now marketed as Gleostine) is an alkylating nitrosourea compound used in chemotherapy. It is closely related to semustine and is in the same family as streptozotocin. It is a high ...

are common chemotherapy agents used to treat mast cell tumors.

Toceranib Toceranib is a receptor tyrosine kinase inhibitor and is used in the treatment of canine mast cell tumor also called mastocytoma. Together with masitinib (Kinavet (US)/Masivet (EU/ROW) by AB Science), toceranib is the only dog-specific anti-canc ...

and

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

, 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 kin ...

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 abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

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

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

. 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 digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...

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

perineum The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), includi ...

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 million y ...

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''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus ...

s and

cattle Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult mal ...

, 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 biology, 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 act together in 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 Boxer most commonly refers to: * Boxer (boxing), a competitor in the sport of boxing *Boxer (dog), a breed of dog Boxer or boxers may also refer to: Animal kingdom * Boxer crab * Boxer shrimp, a small group of decapod crustaceans * Boxer snipe ee ...

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

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 of medium size, a muscular, hefty dog with a wrinkled face and a distinctive pushed-in nose.Basset hound The Basset Hound is a short-legged breed of dog in the hound family. The Basset is a scent hound that was originally bred for the purpose of hunting hare. Their sense of smell and ability to ''ground-scent'' is second only to the Bloodhound.Har ...

Weimaraner The Weimaraner ( ) is a large dog that was originally bred as a hunting dog in the early 19th century. Early Weimaraners were used by royalty for hunting large game such as boar, bear and deer. As the popularity of large game hunting began to ...

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. Color and markings are important when distinguishing this breed f ...

Great Dane The Great Dane is a large sized dog breed originating from Germany. The Great Dane descends from hunting dogs from the Middle Ages used to hunt wild boar and deer, and as guardians of German nobility. It is one of the largest breeds in the world ...

Golden retriever The Golden Retriever is a Scottish breed of retriever dog of medium size. It is characterised by a gentle and affectionate nature and a striking golden coat. It is commonly kept as a pet and is among the most frequently registered breeds ...

* Labrador retriever *

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

German shorthaired pointer The German Shorthaired Pointer (GSP) is a medium to large sized breed of pointing dog developed in the 19th century in Germany for hunting. A versatile hunting breed, being an all-purpose gun dog suitable for both land and water, they are strea ...

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

Pug The Pug is a breed of dog originally from China, with physically distinctive features of a wrinkly, short-muzzled face and curled tail. The breed has a fine, glossy coat that comes in a variety of colors, most often light brown (Fawn (colour) ...

Shar pei The Shar Pei (Cantonese: ''shā pèih'' or Mandarin: 沙皮 ''shā pí'') 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 ...

Rhodesian ridgeback The Rhodesian Ridgeback is a large dog breed bred in the Southern Africa region. Its forebears can be traced to the semi-domesticated ridged hunting and guardian dogs of the Khoikhoi. These were interbred with European dogs by the early colonist ...

Cats

Two types of mast cell tumors have been identified in cats, a mast cell type similar to dogs and a

histiocytic A histiocyte is a vertebrate cell that is part of the mononuclear phagocyte system (also known as the reticuloendothelial system or lymphoreticular system). The mononuclear phagocytic system is part of the organism's immune system. The histiocyt ...

type that appears as subcutaneous nodules and may resolve spontaneously. Young

Siamese cat The Siamese cat ( th, แมวไทย, Maeo Thai; แมวสยาม, Maeo Seeaam) is one of the first distinctly recognized breeds of Asian cat. Derived from the Wichianmat landrace, one of several varieties of cat native to Thailand (f ...

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 The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

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 in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the p ...

, 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 digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces before being r ...

. 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). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlar ...

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 28.8 years. It undergoes β− decay into yttrium-90, with a decay energy of 0.546 MeV. Strontium-90 has applications in medicine and i ...

radiotherapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...

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