Interdigitating dendritic cell sarcoma is a form of malignant histiocytosis affecting dendritic cells.

It can present in the spleen. It can also present in the duodenum.

The disease in the lungs is characterized by enlargement of the tracheobronchial lymph nodes and infiltration of the lungs, sometimes leading to lung lobe consolidation and pleural effusion. Signs and symptoms include cough, loss of appetite, weight loss, anemia, and difficulty breathing. Seizures and rear limb weakness can be seen. Invasion of the bone marrow can cause pancytopenia. Diagnosis requires a biopsy.

Malignant histiocytosis (also known as "Histiocytic medullary reticulosis") 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.

Langhans cells are often found in transbronchial lung biopsies or lymph node biopsies in patients suffering from sarcoidosis.

Unifocal LCH, also called "Eosinophilic Granuloma" (an older term which is now known to be a misnomer), is a slowly progressing disease characterized by an expanding proliferation of Langerhans Cells in various bones. It can be a monostotic (involving only one bone) or polyostotic (involving more than one bone) disease. It typically has no extraskeletal involvement, but rarely an identical lesion can be found in the skin, lungs, or stomach. When found in the lungs, it should be distinguished from Pulmonary Langerhans cell hystiocytosis—a special category of disease most commonly seen in adult smokers. This primary bone involvement helps to differentiate Eosinophilic Granuloma from other forms of Langerhans Cell Histiocytosis (Letterer-Siwe or Hand-Schüller-Christian variant.

The disease spectrum results from clonal accumulation and proliferation of cells resembling the epidermal dendritic cells called Langerhans cells, sometimes called Dendritic Cell Histiocytosis. These cells in combination with lymphocytes, eosinophils, and normal histiocytes form typical LCH lesions that can be found in almost any organ. A similar set of diseases has been described in canine histiocytic diseases.

LCH is clinically divided into three groups: unifocal, multifocal unisystem, and multifocal multisystem.

Langerhans cell sarcoma is a form of malignant histiocytosis. It should not be confused with Langerhans cell histiocytosis, which is cytologically benign. Langerhans cell sarcoma is known to transform into leukemia. It can present in the lung, but such cases are rare.

Langhans giant cells are named after Theodor Langhans (1839–1915), a German pathologist.

They should not be confused with Langerhans cells, which are mononuclear epidermal dendritic cells derived (like Langhans cells) from monocytes and named after Paul Langerhans. (The Islets of Langerhans are also named after Paul Langerhans.)

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. 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.

Most commonly histiocytomas are found in young dogs and appear as a small, solitary, hairless lump, although Shar Peis may be predisposed to multiple histiocytomas. They are most commonly found on the head, neck, ears, and limbs, and are usually less than 2.5 cm in diameter. 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.

X-type histiocytoses are a clinically well-defined group of cutaneous syndromes characterized by infiltrates of Langerhans cells, as opposed to Non-X histiocytosis in which the infiltrates contain monocytes/macrophages. Conditions included in this group are:

Langerhans cells are dendritic cells (antigen-presenting immune cells) of the skin and mucosa, and contain organelles called Birbeck granules. They are present in all layers of the epidermis and are most prominent in the stratum spinosum. They also occur in the papillary dermis, particularly around blood vessels, as well as in the mucosa of the mouth, foreskin, and vagina. They can be found in other tissues, such as lymph nodes, particularly in association with the condition Langerhans cell histiocytosis (LCH).

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:

The disease is often rapidly fatal, with a five year survival rate of 50%. The development of thrombocytopenia is a poor prognostic sign.

.Letterer-Siwe is characterized by skin lesions, ear drainage, lymphadenopathy, osteolytic lesions, and hepatosplenomegaly. The skin lesions are scaly and may involve the scalp, ear canals, and abdomen.

Dermatopathic lymphadenopathy is diagnosed by a lymph node biopsy. It has a characteristic pattern of histomorphology and immunohistochemical staining:

- Paracortical histiocytosis

- Melanin-laden macrophages

- Eosinophils

- Plasma cells (medulla of lymph node)

Eosinophilic granuloma is a form of Langerhans cell histiocytosis. It is a condition of both human and veterinary pathology. Colloquially, the reaction pattern is sometimes referred to as a rodent ulcer.

Feline eosinophilic granuloma complex is synonymous with "feline eosinophilic skin diseases". This is considered to be a cutaneous reaction pattern that can be the manifestation of a number of underlying infections, allergies or ectoparasite infestations. It can also be idiopathic, that is have no known underlying trigger. The eosinophilic reaction is common in feline inflammatory disease and the eosinophilic granuloma can be a hereditary reaction pattern in some lines of domestic cats.

Cats with eosinophilic granuloma complex (EGC) may have one or more of four patterns of skin disease.

The most frequent form is "eosinophilic plaque". This is a rash comprising raised red to salmon-colored and flat-topped, moist bumps scattered on the skin surface. The most common location is on the ventral abdomen and inner thigh.

Another form of EGC is the "lip ulcer". This is a painless, shallow ulcer with raised and thickened edges that forms on the upper lip adjacent to the upper canine tooth. It is often found on both sides of the upper lips.

The third form of the EGC is the "collagenolytic granuloma". This is a firm swelling that may be ulcerated. The lesions may form on the skin, especially of the face, in the mouth, or on the feet, or may form linear flat-topped raised hairless lesions on the back of the hind legs, also called "linear granuloma".

The least common form of EGC is "atypical eosinophilic dermatitis". It is unique in that it is caused by mosquito bite allergy and the lesions form on the parts of the body with the least hair affording easy access to feeding mosquitoes. This includes the bridge of the nose, the outer tips of the ears and the skin around the pads of the feet. The lesions are red bumps, shallow ulcers and crusts.

A histiocyte is an animal 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 histiocyte is a tissue macrophage or a dendritic cell (histio, diminutive of histo, meaning "tissue", and cyte, meaning "cell").

In pathology, dermatopathic lymphadenopathy, also dermatopathic lymphadenitis, is lymph node pathology due to skin disease.

In medicine, histiocytosis refers to an excessive number of histiocytes, ("tissue macrophages"), and is typically used to refer to a group of rare diseases which share this as a characteristic. Occasionally and confusingly, the term "histiocytosis" is sometimes used to refer to individual diseases.

According to the Histiocytosis Association of America, 1 in 200,000 children in the United States are born with histiocytosis each year. HAA also states that most of the people diagnosed with histiocytosis are children under the age of 10, although the disease can afflict adults. The University of California, San Francisco, states that the disease usually occurs from birth to age 15.

Histiocytosis (and malignant histiocytosis) are both important in veterinary as well as human pathology.

Hand–Schüller–Christian disease is associated with multifocal Langerhans cell histiocytosis.

It is associated with a triad of exophthalmos, lytic bone lesions (often in the skull), and diabetes insipidus (from pituitary stalk infiltration).

It is named for the US-American pediatrician Alfred Hand Jr, the Austrian neurologist and radiologist Arthur Schüller, and the US-American internist Henry Asbury Christian, who described it in 1893, 1915/16 and 1919

Lymphadenopathy can occur in one or more groups of lymph nodes. Among 358 cases of Rosai–Dorfman disease that Rosai collected in a disease registry for which the location of lymphadenopathy was specified, 87.3% had cervical lymphadenopathy. Axillary, inguinal, and mediastinal lymphadenopathy are also found in Rosai–Dorfman disease.

The histiocytosis of Rosai–Dorfman disease can occur in lymph nodes, causing lymphadenopathy, or can occur outside lymph nodes in extranodal disease.

Dendritic cells (DCs) are antigen-presenting cells (also known as "accessory cells") of the mammalian immune system. Their main function is to process antigen material and present it on the cell surface to the T cells of the immune system. They act as messengers between the innate and the adaptive immune systems.

Dendritic cells are present in those tissues that are in contact with the external environment, such as the skin (where there is a specialized dendritic cell type called the Langerhans cell) and the inner lining of the nose, lungs, stomach and intestines. They can also be found in an immature state in the blood. Once activated, they migrate to the lymph nodes where they interact with T cells and B cells to initiate and shape the adaptive immune response. At certain development stages they grow branched projections, the "dendrites" that give the cell its name (δένδρον or déndron being Greek for "tree"). While similar in appearance, these are structures distinct from the dendrites of neurons. Immature dendritic cells are also called veiled cells, as they possess large cytoplasmic 'veils' rather than dendrites.