Mastocytoma | |
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Other names | Mast cell tumor |
Mast cell tumor cytology | |
Specialty | Oncology |
A mastocytoma or mast cell tumor is a type of round-cell tumor consisting of mast cells. 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 and are normally found throughout the connective tissue of the body as normal components of the immune system. As they release histamine, they are associated with allergic reactions. Mast cells also respond to tissue trauma. Mast cell granules contain histamine, heparin, platelet-activating factor, and other substances. Disseminated mastocytosis 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, [1] with a similar number in cats. [2]
When mastocytomas affect humans, they are typically found in skin. [3] They usually occur as a single lesion on the trunk or wrist. Although it is rare, mastocytomas are sometimes found in the lung. [3] It can also affect children. [4]
Mast cell tumors are known among veterinary oncologists as 'the great pretenders' because their appearance can be varied, from a wart-like nodule to a soft subcutaneous lump (similar on palpation to a benign lipoma) 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 [5] (especially in Boxers and Pugs). [6]
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, diarrhea, and anemia. The presence of these signs usually indicates mastocytosis, 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 and duodenum (present in up to 25 percent of cases) [6] or disseminated intravascular coagulation. When metastasis does occur, it is usually to the liver, spleen, lymph nodes and bone marrow.
A needle aspiration biopsy 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, and the cells are medium-sized. [7] However, a surgical biopsy is required to find the grade of the tumor. The grade depends on how well the mast cells are differentiated, mitotic activity, location within the skin, invasiveness, and the presence of inflammation or necrosis. [8]
However, there is a significant amount of discordance between veterinary pathologists in assigning grades to mast cell tumors due to imprecise criteria. [9]
The disease is also staged according to the WHO system:
X-rays, ultrasound, or lymph node, bone marrow, or organ biopsies may be necessary to stage the disease.
Removal of the mast cell tumor through surgery is the treatment of choice. Antihistamines, such as diphenhydramine, 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 or chemotherapy, may be necessary. Prednisone is often used to shrink the remaining tumor portion. H2 blockers, such as cimetidine, protect against stomach damage from histamine. Vinblastine and lomustine are common chemotherapy agents used to treat mast cell tumors. [5]
Toceranib and masitinib, examples of receptor tyrosine kinase inhibitors, are used in the treatment [11] [12] of canine mast cell tumors. Both were recently approved by the U.S. Food and Drug Administration (FDA) [13] [14] as dog-specific anticancer drugs. [15]
Grade I or II mast cell tumors that can be completely removed have a good prognosis. One study showed about 23 percent of incompletely removed grade II tumors recurred locally. [16] Any mast cell tumor found in the gastrointestinal tract, paw, or on the muzzle has a guarded prognosis. Previous beliefs that tumors in the groin or perineum carried a worse prognosis have been discounted. [17] 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. [10] Multiple tumors that are treated similarly to solitary tumors do not seem to have a worse prognosis. [18]
Mast cell tumors do not necessarily follow the histological prognosis. Further prognostic information can be provided by AgNOR stain of histological or cytological specimen. [19] Even then, there is a risk of unpredictable behavior.
Mast cell tumors are an uncommon occurrence in horses. They usually occur as benign, solitary masses on the skin of the head, neck, trunk, and legs. Mineralization of the tumor is common. [20] In pigs and cattle, mast cell tumors are rare. They tend to be solitary and benign in pigs and multiple and malignant in cattle. [6] Mast cell tumors are found in the skin of cattle most commonly, but these may be metastases from tumors of the viscera. [21] Other sites in cattle include the spleen, muscle, gastrointestinal tract, omentum, and uterus. [22]
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:
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 cats are at an increased risk for the histiocytic type, [2] although the mast cell type is the most common in all cats and is considered to be benign when confined to the skin. [6]
Mast cell tumors of the skin are usually located on the head or trunk. [24] Gastrointestinal and splenic involvement is more common in cats than in dogs; 50 percent of cases in dogs primarily involved the spleen or intestines. [25] Gastrointestinal mast cell tumors are most commonly found in the muscularis layer of the small intestine, but can also be found in the large intestine. [26] It is the third most common intestinal tumor in cats, after lymphoma and adenocarcinoma. [27]
Diagnosis and treatment are similar to that of the dog. Cases involving difficult to remove or multiple tumors have responded well to strontium-90 radiotherapy as an alternative to surgery. [28] The prognosis for solitary skin tumors is good, but guarded for tumors in other organs. Histological grading of tumors has little bearing on prognosis. [29]
Gastric dilatation volvulus (GDV), also known as gastric dilation, twisted stomach, or gastric torsion, is a medical condition that affects dogs and rarely cats and guinea pigs, in which the stomach becomes overstretched and rotated by excessive gas content. The condition also involves compression of the diaphragm and caudal vena cavae. The word bloat is often used as a general term to mean gas distension without stomach torsion, or to refer to GDV.
A canine transmissible venereal tumor (CTVT), also known as a transmissible venereal tumor (TVT), canine transmissible venereal sarcoma (CTVS), sticker tumor and infectious sarcoma, is a histiocytic tumor of the external genitalia of the dog and other canines, and is transmitted from animal to animal during mating. It is one of only three known transmissible cancers in mammals; the others are devil facial tumor disease, a cancer which occurs in Tasmanian devils, and contagious reticulum cell sarcoma of the Syrian hamster.
The health of dogs is a well studied area in veterinary medicine.
Lymphoma (lymphosarcoma) in animals is a type of cancer defined by a proliferation of malignant lymphocytes within solid organs such as the lymph nodes, bone marrow, liver and spleen. The disease also may occur in the eye, skin, and gastrointestinal tract.
Protothecosis, otherwise known as Algaemia, is a disease found in dogs, cats, cattle, and humans caused by a type of green alga known as Prototheca that lacks chlorophyll and enters the human or animal bloodstream. It and its close relative Helicosporidium are unusual in that they are actually green algae that have become parasites. The two most common species are Prototheca wickerhamii and Prototheca zopfii. Both are known to cause disease in dogs, while most human cases are caused by P. wickerhami. Prototheca is found worldwide in sewage and soil. Infection is rare despite high exposure, and can be related to a defective immune system. In dogs, females and Collies are most commonly affected.
Phycomycosis is an uncommon condition affecting the gastrointestinal tract and skin, most commonly found in dogs and horses. The condition is caused by various molds and fungi, with individual forms including pythiosis, zygomycosis, and lagenidiosis. Pythiosis, the most common type, is caused by Pythium, a type of water mould. Zygomycosis can be caused by two types of zygomycetes: Entomophthorales and Mucorales. The latter type of zygomycosis is also referred to as mucormycosis. Lagenidiosis is caused by a Lagenidium species, which like Pythium is a water mould. Since both pythiosis and lagenidiosis are caused by organisms from the Oomycetes and not the kingdom fungi, they are sometimes collectively referred to as oomycosis.
Pythiosis is a rare and deadly tropical disease caused by the oomycete Pythium insidiosum. Long regarded as being caused by a fungus, the causative agent was not discovered until 1987. It occurs most commonly in horses, dogs, and humans, with isolated cases in other large mammals. The disease is contracted after exposure to stagnant fresh water such as swamps, ponds, lakes, and rice paddies. P. insidiosum is different from other members of the genus in that human and horse hair, skin, and decaying animal and plant tissue are chemoattractants for its zoospores. Additionally, it is the only member in the genus known to infect mammals, while other members are pathogenic to plants and are responsible for some well-known plant diseases.
Hypertrophic osteopathy is a bone disease secondary to cancer in the lungs.
Granulomatous meningoencephalitis (GME) is an inflammatory disease of the central nervous system (CNS) of dogs and, rarely, cats. It is a form of meningoencephalitis. GME is likely second only to encephalitis caused by canine distemper virus as the most common cause of inflammatory disease of the canine CNS. The disease is more common in female dogs of young and middle age. It has a rapid onset. The lesions of GME exist mainly in the white matter of the cerebrum, brainstem, cerebellum, and spinal cord. The cause is only known to be noninfectious and is considered at this time to be idiopathic. Because lesions resemble those seen in allergic meningoencephalitis, GME is thought to have an immune-mediated cause, but it is also thought that the disease may be based on an abnormal response to an infectious agent. One study searched for viral DNA from canine herpesvirus, canine adenovirus, and canine parvovirus in brain tissue from dogs with GME, necrotizing meningoencephalitis, and necrotizing leukoencephalitis, but failed to find any.
Lymphangiectasia, also known as "lymphangiectasis", is a pathologic dilation of lymph vessels. When it occurs in the intestines it is known as intestinal lymphangiectasia, colloquially recognized as Waldmann's disease in cases where there is no secondary cause. The primary defect lies in the inability of the lymphatic system to adequately drain lymph, resulting in its subsequent accumulation and leakage into the intestinal lumen. This condition, first described by Waldmann in 1961, is typically diagnosed in infancy or early childhood. However, it can also manifest in adults, exhibiting a broad spectrum of clinical symptoms.
A mammary tumor is a neoplasm originating in the mammary gland. It is a common finding in older female dogs and cats that are not spayed, but they are found in other animals as well. The mammary glands in dogs and cats are associated with their nipples and extend from the underside of the chest to the groin on both sides of the midline. There are many differences between mammary tumors in animals and breast cancer in humans, including tumor type, malignancy, and treatment options. The prevalence in dogs is about three times that of women. In dogs, mammary tumors are the second most common tumor over all and the most common tumor in female dogs with a reported incidence of 3.4%. Multiple studies have documented that spaying female dogs when young greatly decreases their risk of developing mammary neoplasia when aged. Compared with female dogs left intact, those spayed before puberty have 0.5% of the risk, those spayed after one estrous cycle have 8.0% of the risk, and dogs spayed after two estrous cycles have 26.0% of the risk of developing mammary neoplasia later in life. Overall, unspayed female dogs have a seven times greater risk of developing mammary neoplasia than do those that are spayed. While the benefit of spaying decreases with each estrous cycle, some benefit has been demonstrated in female dogs even up to 9 years of age. There is a much lower risk in male dogs and a risk in cats about half that of dogs.
A perianal gland tumor is a type of tumor found near the anus in dogs that arises from specialized glandular tissue found in the perineum. It is also known as a hepatoid tumor because of the similarity in cell shape to hepatocytes. It is most commonly seen in intact dogs and is the third most common tumor type in intact male dogs. There are two types of perianal gland tumors, perianal gland adenomas, which are benign, and perianal gland adenocarcinomas, which are malignant. Both have receptors for testosterone. Perianal gland adenomas are three times more likely to be found in intact male dogs than females, and perianal gland adenocarcinomas are ten times more common in male dogs than females. The most commonly affected breeds for adenomas are the Siberian Husky, Cocker Spaniel, Pekingese, and Samoyed; for adenocarcinomas the most commonly affected breeds are the Siberian Husky, Bulldog, and Alaskan Malamute.
An anal sac adenocarcinoma is an uncommon and aggressive malignant tumor found in dogs that arises from the apocrine glandular tissue of anal sac. The disease exists in cats as well, but is much less common in that species. They are the second most common cancerous cause of hypercalcaemia in dogs, following T-cell lymphoma.
A vaccine-associated sarcoma (VAS) or feline injection-site sarcoma (FISS) is a type of malignant tumor found in cats which has been linked to certain vaccines. VAS has become a concern for veterinarians and cat owners alike and has resulted in changes in recommended vaccine protocols. These sarcomas have been most commonly associated with rabies and feline leukemia virus vaccines, but other vaccines and injected medications have also been implicated.
Cancer in cats is the leading cause of death among cats. It is caused by uncontrolled cell growth, and affects a wide range of cell types and organs in the body. Feline cancer initially manifests as a lump or bump on any parts of the body. It rapidly grows in the affected cell, attaches itself to the tissue under the skin in that area, and, depending on the tumour, it can spread to other parts of the body. Although cancer accounts for approximately 32% of deaths in cats over ten years old, it can be successfully treated if diagnosed early.
Cancer is the leading cause of death in dogs. It is estimated that 1 in 3 domestic dogs will develop cancer, which is the same incidence of cancer among humans. Dogs can develop a variety of cancers and most are very similar to those found in humans. Dogs can develop carcinomas of epithelial cells and organs, sarcomas of connective tissues and bones, and lymphomas or leukemias of the circulatory system. Selective breeding of dogs has led certain pure-bred breeds to be at high-risk for specific kinds of cancer.
Toceranib (INN), sold under the brand name Palladia, is a receptor tyrosine kinase inhibitor that is used in the treatment of canine mast cell tumor also called mastocytoma. It is the first medication developed specifically for the treatment of cancer in dogs. It is used as its phosphate salt, toceranib phosphate. It was developed by SUGEN as SU11654, a sister compound to sunitinib, which was later approved for human therapies. Toceranib is a tyrosine kinase inhibitor and works in two ways: by killing tumor cells and by cutting off the blood supply to the tumor.
An equine melanoma is a tumor that results from the abnormal growth of melanocytes in horses. Unlike in humans, melanomas in horses are not thought to be caused by exposure to ultraviolet light. Melanomas are the third most common type of skin cancer in horses, with sarcoids being the first most prevalent and squamous-cell carcinoma being second. Melanomas are typically rounded black nodules that vary in size and are usually found underneath the dock of the tail, in the anal, perianal and genital regions, on the perineum, lips, eyelids, and sometimes near the throatlatch.
A mastocytoma in dogs is a neoplasm (neoplasia) originating from mast cells in the domestic dog, which occurs mainly in the skin and subcutis. Mastocytoma are not only extremely common in dogs, but also tend to be much more malignant in them than in other animal species. The average survival time for malignant tumors is only four months, whereas for benign tumors it is over two years.