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Malignant Histiocytosis In Dogs

Malignant Histiocytosis In Dogs

Histiocytosis is an umbrella term for an emerging spectrum of "syndromes" or disorders that involve abnormal proliferation of specialized white blood cells (histiocytes). Histiocytes are derived from monocytes, a category of leukocytes that function as part of the immunological barrier against foreign organisms that would invade the skin. In the case of histiocytomas, the reproductive mechanism of these histiocytes which are self-regulatory becomes disarray.

In general, Histiocytosis refers to an abnormally large amount of histiocytes. There are many different types of histiocytosis.

Recently, a new understanding of this group of diseases has led experts to develop a new classification.

There are five categories of Histiocytosis:

  1. C group: Non-Langerhans Cell Histiocytosis (skin).
  2. H group: Haemophagocytic Lymphohistiocytosis.
  3. L group: Erdheim-Chester Disease, Langerhans Cell Histiocytosis, etc.
  4. M group: Includes Malignant Histiocytosis.
  5. R group: Includes Rosai-Dorfman Disease.

Malignant histiocytic diseases include malignant histiocytosis (now it is called localized and disseminated histiocytic sarcoma) and cutaneous histiocytoma, which is a benign histiocytic tumor. The histiocytic disease differentiation can be challenging.

A cutaneous histiocytoma is an abnormal proliferation of histiocytes in Langerhans cells. The first 1 - 4 weeks is the period of rapid growth, they often ulcerate and get infected.

Malignant Histiocytoma is an aggressive, pedunculated, or nodular neoplasm that arises from monocyte-macrophage cells in the skin. They are usually firm and well-circumscribed but sometimes, on palpation feel soft. The overlying hyperpigmented skin is keratotic or shiny and when the tumor is pinched, there is a depression on the surface.

Symptoms Of Malignant Histiocytosis

  • Nodular Lesions
  • Smooth / Ulcerous / Hairless / Crusted lesions.
  • Lesions in mucous membranes, nose, eyelids, extremities, and scrotum.
  • Purpura
  • Difficulty breathing
  • Anemia
  • Edema
  • Crusting / Scaling
  • Erosions
  • Hyperpigmentation
  • Neurological disturbances
  • Paralysis
  • Seizures

Treatment Options For Malignant Histiocytosis

  • Treatment protocol for malignant histiocytosis is directed towards controlling the local tumor and tackling the concern for metastasis.
  • For local control, the most common options implemented are surgery and/or radiation therapy.
  • Chemotherapy is performed as a rescue choice for tumors that have started to metastasize or recurred.
  • Broad-spectrum antibiotics.

Home Remedies For Malignant Histiocytosis

Malignant histiocytosis cannot be completely cured even with medical management. Discuss home treatments with your vet to ensure there won’t mess with other medications.

Prevention Of Malignant Histiocytosis

  • Prevention is not possible for histiocytosis as the causes are still unknown.
  • Good overall health and early detection are the only ways to prevent histiocytosis.
  • Pay attention to sudden changes in appetite and weight.
  • Home-prepared diets are good for dogs than dry and canned dog foods.

Affected Breeds Of Malignant Histiocytosis

Bernese Mountain Dog, Boxer, Briard, Bull Terrier, Shar Pei, Cocker Spaniel, Collie, Dachshund, Flat Coated Retriever, German Shepherd, Golden Retriever, Great Dane, Rottweiler, Shetland Sheepdog, Bichon Frise, Maltese, Pekingese, Poodle, Skye Terrier

Additional Facts For Malignant Histiocytosis

  1. Causes:
  • Mostly congenital/idiopathic.
  • Allergic skin diseases (e.g., flea allergy dermatitis, atopic dermatitis).
  • Infections (bacterial, fungal, Viral - Coronavirus, Parvovirus).
  • Exposure to herbicides, pesticides, and insecticides.
  1. Types:
  • Nonmalignant Nonneoplastic - Reactive (cutaneous or systemic) histiocytosis.
  • Nonmalignant Neoplastic - Cutaneous histiocytoma.
  • Malignant Neoplastic - Localized histiocytic sarcoma, Disseminated histiocytic sarcoma.
  1. Mortality:

Malignant Histiocytosis is a potentially life-threatening disease in dogs but the mortality rate of dogs is not documented.

  1. Diagnosis:
  • Routine hematology
  • Urinalysis
  • Surgical biopsy
  • Histopathological examination of the skin.
  • Rickettsial screening
  • Fungal culture
  • Bacterial culture
  1. Differential Diagnosis:
  • Angioedema
  • Adverse Cutaneous Drug Reaction
  • Canine Distemper
  • Chin Pyoderma
  • Demodicosis
  • Dermatophytosis
  1. Prognosis:

Malignant histiocytosis prognosis for recovery is poor. If tumors have not metastasized to internal organs, the prognosis can be good. However, these are aggressive tumors and can rapidly spread into internal organs, highlighting the need to identify and treat this condition immediately.

When To See A Vet

Contact your vet right away, if you notice any of the following:

  • Nodular Lesions
  • Smooth / Ulcerous / Hairless / Crusted lesions.
  • Lesions in mucous membranes, nose, eyelids, extremities, and scrotum.

Food Suggestions For Malignant Histiocytosis

  • Protein - Liver, chicken/turkey breasts, ½ Cup cooked or raw Salmon.
  • Lean meats, such as chicken breast, sirloin, or pork.
  • Low fat, high protein foods - Skinless White-Meat Poultry, White-Fleshed Fish, Beans, Peas, and Lentils.
  • DHA - Sardines, mackerel, salmon, herring, caviar, etc.
  • Antioxidants - Blackberries, Blueberries, steamed broccoli, spinach, cooked yellow squash, green beans, and kale.
  • Fats- beef tallow or Chicken/turkey fat.


Dogs with malignant histiocytosis often survive for 1 - 2 months without radiation and chemotherapy, but with treatment, the prognosis is even better. Dogs can have an improved quality of life for a period of time with proper treatment.

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