Malignant histiocytosis

Malignant histiocytosis or Histiocytic sarcoma is a cancer of the dog, which occurs mainly in the Bernese mountain dog and this breed as a genetic disease is a leading cause of death. In other breeds, the disease is rare. Malignant histiocytosis may occur as a skin form (" cutaneous histiocytosis " ) or as a generalized form ( " disseminated histiocytosis ").

Pathophysiology

Histiocytes occurring particularly in the connective tissue cells, which belong to the macrophages in the tissue and perform certain functions of the immune system. Mutation of these cells can degenerate into malignant cells to form a tumor, which has a marked tendency to metastasis. These metastases destroy by their uncontrolled and invasive growth of vital organs, leading eventually to the death of the dog.

Clinic

Signalment

On malignant histiocytosis typically ill young to middle-aged dogs between the ages of two to eight years. Males are more frequently affected than females. The vast majority of cases occur in the Bernese Mountain Dog. Sporadic cases can generally occur in all races, with some accumulation at the Flat Coated Retriever, Golden Retriever, Irish Wolfhound and Rottweiler is described.

Symptoms

From the skin form of affected dogs show nodes and plaque formation in the skin - especially on the scrotum in males - as well as the nasal and ocular mucosa. The lesions are poorly limited, occasionally accompanied by alopecia and may ulcerate. They develop in spurts and can also gradually decline again after a thrust to appear again after a few months. The disease usually gets worse with each new thrust. The lesions can spread to other organs, particularly the lymph nodes, spleen and bone marrow.

Disseminated malignant histiocytosis usually occurs without involvement of the skin. The most commonly affected are the lungs, lymph nodes and liver. Affected dogs show weakness, loss of appetite, fatigue, weight loss and breathing problems; rare problems swallowing or coughing. The tumors appear as large, single, solid lesions that destroy the organs affected by their invasive growth. The disseminated form does not run in spurts, but rapidly progressive and leads in the vast majority of cases, in less than six months to death.

Diagnosis

A suspected cutaneous histiocytosis results from the typical signalment of the dog in conjunction with the main symptoms. Disseminated histiocytosis often shows up already in the radiograph, particularly where lung metastases and bone metastases can be seen. The confirmation of the diagnosis is made by microscopic examination of biopsies taken from suspicious tissue masses.

Treatment and prognosis

There is no satisfactory treatment of malignant histiocytosis. Surgical excision is rarely practicable, and the tumors respond very sensitive to radiation and chemotherapy. The treatment is therefore palliative in most cases. Bovine thymosin 5 showed limited success in the treatment of the skin shape. The life expectancy following diagnosis is a few months, a few dogs survive longer than six months.

Genetics and breeding hygiene

Malignant histiocytosis in the Bernese mountain dog follows a polygenic inheritance. In this race different breed clubs to combat the disease have introduced a breeding value estimation.