A histiocytoma in the dog is a benign tumor. It is an abnormal growth in the skin of histiocytes (histiocytosis), a cell that is part of the immune system. A similar disease in humans, Hashimoto-Pritzker disease, is also a Langerhans cell histiocytosis. [1] Dog breeds that may be more at risk for this tumor include Bulldogs, American Pit Bull Terriers, American Staffordshire Terriers, Scottish Terriers, Greyhounds, Boxers, and Boston Terriers. They also rarely occur in goats and cattle. [2]
A histiocyte is a differentiated tissue cell that has its origin in the bone marrow. The source for histiocytes is the monocyte/macrophage line. Monocytes (found in the blood) and macrophages (found in tissue) are responsible for phagocytosis (ingestion) of foreign material in the body. Langerhans cells are dendritic cells found in the skin and function by internalizing antigens (foreign particles) and presenting them to T cells. They arise from monocytes. [3] Histiocytic disorders refer to diseases that are caused by abnormal behavior of these cells. They include the following:
A histiocytoma originates from epidermal Langerhans cells of antigen-presenting cell lineage. [4] Spontaneous regression is common in these tumors, and it is mediated by infiltration of CD8-expressing T cells followed by expression of Type 1 T helper cell cytokines (such as Interferon-gamma) and recruitment of antitumour effector cells. [5]
Most commonly histiocytomas are found in young dogs and appear as a small, solitary, hairless lump, [6] although Shar Peis may be predisposed to multiple histiocytomas. [7] They are most commonly found on the head, neck, ears, and limbs, and are usually less than 2.5 cm in diameter. [8] Ulceration of the mass is common. Diagnosis is made through cytology of the mass. Cytology reveals cells with clear to lightly basophilic cytoplasm and round or indented nuclei with fine chromatin and indistinct nucleoli. [9]
Most histiocytomas will regress within two or three months. [6] Surgical removal may be necessary if the tumor does not regress or if it is growing rapidly to a large size. Histiocytomas should never be treated with an intralesional injection of a corticosteroid, as remission relies on recognition of the tumour by the body's immune system which is suppressed by steroids.
Tumors of the hematopoietic and lymphoid tissues or tumours of the haematopoietic and lymphoid tissues are tumors that affect the blood, bone marrow, lymph, and lymphatic system. Because these tissues are all intimately connected through both the circulatory system and the immune system, a disease affecting one will often affect the others as well, making aplasia, myeloproliferation and lymphoproliferation closely related and often overlapping problems. While uncommon in solid tumors, chromosomal translocations are a common cause of these diseases. This commonly leads to a different approach in diagnosis and treatment of hematological malignancies. Hematological malignancies are malignant neoplasms ("cancer"), and they are generally treated by specialists in hematology and/or oncology. In some centers "hematology/oncology" is a single subspecialty of internal medicine while in others they are considered separate divisions. Not all hematological disorders are malignant ("cancerous"); these other blood conditions may also be managed by a hematologist.
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.
Fibrosarcoma is a malignant mesenchymal tumour derived from fibrous connective tissue and characterized by the presence of immature proliferating fibroblasts or undifferentiated anaplastic spindle cells in a storiform pattern. Fibrosarcomas mainly arise in people between the ages of 25 and 79. It originates in fibrous tissues of the bone and invades long or flat bones such as the femur, tibia, and mandible. It also involves the periosteum and overlying muscle.
Langerhans cell histiocytosis (LCH) is an abnormal clonal proliferation of Langerhans cells, abnormal cells deriving from bone marrow and capable of migrating from skin to lymph nodes.
A histiocyte is a vertebrate cell that is part of the mononuclear phagocyte system. The mononuclear phagocytic system is part of the organism's immune system. The histiocyte is a tissue macrophage or a dendritic cell. Part of their job is to clear out neutrophils once they've reached the end of their lifespan.
The International Classification of Diseases for Oncology (ICD-O) is a domain-specific extension of the International Statistical Classification of Diseases and Related Health Problems for tumor diseases. This classification is widely used by cancer registries.
Malignant histiocytosis is a rare hereditary disease found in the Bernese Mountain Dog and humans, characterized by histiocytic infiltration of the lungs and lymph nodes. The liver, spleen, and central nervous system can also be affected. Histiocytes are a component of the immune system that proliferate abnormally in this disease. In addition to its importance in veterinary medicine, the condition is also important in human pathology.
A histiocytoma is a tumour consisting of histiocytes. Histiocytes are cells that are a part of the mononuclear phagocytic system, a part of the body's immune system that consists of phagocytic cells, which are responsible for engulfing solid particles by the cell membrane to form an internal phagosome by phagocytes and protists. Myxofibrosarcoma had been classified as a type of histiocytoma. However, the World Health Organization (2020) reclassified myxofibrosarcoma as a malignant tumor in the category of fibroblastic/myofibroblastic tumors.
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.
In medicine, histiocytosis is an excessive number of histiocytes, and the term is also often used to refer to a group of rare diseases which share this sign as a characteristic. Occasionally and confusingly, the term histiocytosis is sometimes used to refer to individual diseases.
Chronic multifocal Langerhans cell histiocytosis, previously known as Hand–Schüller–Christian disease, is a type of Langerhans cell histiocytosis (LCH), which can affect multiple organs. The condition is traditionally associated with a combination of three features; bulging eyes, breakdown of bone, and diabetes insipidus, although around 75% of cases do not have all three features. Other features may include a fever and weight loss, and depending on the organs involved there may be rashes, asymmetry of the face, ear infections, signs in the mouth and the appearance of advanced gum disease. Features relating to lung and liver disease may occur.
Lymphoid hyperplasia is the rapid proliferation of normal lymphocytic cells that resemble lymph tissue which may occur with bacterial or viral infections. The growth is termed hyperplasia which may result in enlargement of various tissue including an organ, or cause a cutaneous lesion.
Rosai–Dorfman disease, also known as sinus histiocytosis with massive lymphadenopathy or sometimes as Destombes–Rosai–Dorfman disease, is a rare disorder of unknown cause that is characterized by abundant histiocytes in the lymph nodes or other locations throughout the body.
Langerhans cell sarcoma (LCS) is a rare form of malignant histiocytosis. It should not be confused with Langerhans cell histiocytosis, which is cytologically benign. It can present most commonly in the skin and lymphatic tissue, but may also present in the lung, liver, and bone marrow. Treatment is most commonly with surgery or chemotherapy.
Non-Langerhans cell histiocytosis refers to a family of histiocytosis characterized by the absence of Langerhans cells.
Non-X histiocytoses are a clinically well-defined group of cutaneous syndromes characterized by infiltrates of monocytes/macrophages, as opposed to X-type histiocytoses in which the infiltrates contain Langerhans cells. Conditions included in this group are:
Histiocytic diseases in dogs are a group of diseases in dogs which may involve the skin, and which can be difficult to differentiate from granulomatous, reactive inflammatory or lymphoproliferative diseases. The clinical presentation and behaviour as well as response to therapy vary greatly among the syndromes.
The Xanthogranulomatous Process (XP), is a form of acute and chronic inflammation characterized by an exuberant clustering of foamy macrophages among other inflammatory cells. Localization in the kidney and renal pelvis has been the most frequent and better known occurrence followed by that in the gallbladder but many others have been subsequently recorded. The pathological findings of the process and etiopathogenetic and clinical observations have been reviewed by Cozzutto and Carbone.
Crystal-storing histiocytosis is a form of histiocytosis which mostly occurs in people with monoclonal gammopathies. Histiocytosis is an excessive number of histiocytes. In the vast majority of crystal-storing histiocytosis cases, immunoglobulins accumulate within the cytoplasm of histiocytes; in rare cases clofazimine, cystine, silica, or Charcot–Leyden crystals may be found in the histiocytes instead. Non-immunoglobulin crystal-storing histiocytosis is mostly associated with non-malignant disorders, such as chronic inflammation or autoimmune abnormality conditions such as rheumatoid arthritis, Crohn's disease, or Helicobacter pylori gastritis. It may be a localised or generalised disease. Examples of locations where histiocytosis may occur include the lungs, pleura, stomach, kidney, bone marrow, thyroid, thymus, and parotid gland. The disease is described as generalised if two or more unrelated sites are involved.