What are Histiocytosis?
Histiocytosis refers to an abnormally large amount of histiocytes, which are the white blood cells in the immune system that come from the bone marrow. There are two kinds of histiocytes, which are macrophages, which remove debris and other foreign materials from the blood, and dendritic cells that tell the lymphocytes what molecules are good and which are bad. Both CCH and CH produce benign tumors that are restricted to the skin and may come and go at will. SH is a more serious form that involves the organs as well as the skin and lymph nodes although it is not malignant. HS and MH are both malignant tumors that are life threatening. Removing the tumor before it spreads is the best form of treatment because once it spreads into the vital organs, it is almost always fatal.
There are several different types of histiocytosis, which are reactive histiocytosis (includes cutaneous and systemic), canine cutaneous histiocytoma, and histiocytic sarcoma complex (includes histiocytic sarcoma and malignant histiocytosis). Cutaneous reactive histiocytosis (CH) and canine cutaneous histiocytoma (CCH) are benign skin tumors that come and go but do not cause any internal damage. Systemic reactive histiocytosis (SH) causes skin tumors that progress to the vital organs and bone marrow and can be unresponsive to treatment. Histiocytic sarcoma (HS) is a malignant tumor that can spread quickly without treatment. Malignant histiocytosis (MH) is an aggressive disease with several tumors that progresses quickly and is usually fatal.
Symptoms of Histiocytosis in Dogs
There are several types of histiocytosis and each have their own set of side effects. Some of these are:
Canine cutaneous histiocytoma (CCH) and cutaneous histiocytosis (CH)
- Nodular lesions of various sizes that can be up to 4 centimeters, smooth, hairless, ulcerous, or crusted.
- Lesions are distributed anywhere on the body, most common in extremities, scrotum, mucous membranes, nose, and eyelids.
- In CCH, the lesions usually clear up on their own.
- CH tumors come and go randomly.
Systemic histiocytosis (SH)
- Skin lesions identical to CH
- Appetite loss
- Swelling of the inner eye
- Inflammation or edema
- Swollen lymph nodes
- Muscle spasms
- Depression
Histiocytic sarcoma (HS)
- Single skin lesion
- Fast growing tumor
- May spread to internal tumors that can cause symptoms related to the location
Malignant histiocytosis (MH)
- Fever
- Depression
- Lethargy
- Appetite loss
- Weight loss
- Cough
- Vomiting
- Diarrhea
- Trouble breathing
Types
- Canine cutaneous histiocytoma (CCH) is just one benign lesion that affects mostly younger dogs that clears up on its own
- Cutaneous histiocytosis (CH) one to five lesions that seem to come and go at will
- Systemic histiocytosis (SH) causes lesions in the skin as well as internal organs, bone marrow, and lymph nodes, but it is not malignant
- Histiocytic sarcoma (HS) is a malignant tumor localized to one area at first. It has to be removed quickly before it spreads or it is fatal
- Malignant histiocytosis (MH) is an aggressive form that causes multiple cancerous tumors on the skin and in the vital organs. This disease is almost always fatal
Causes of Histiocytosis in Dogs
The cause of most histiocytoses are unknown, but they are most often seen in:
- Dogs over 5-7 years
- Bernese Mountain Dogs
- Briards
- Chinese Shar Peis
- Collies
- German Shepherds
- Golden Retrievers
- Rottweilers
- Shetland Sheepdogs
Diagnosis of Histiocytosis in Dogs
The veterinarian will perform a physical examination to check vitals and examine your dog from head to tail for signs of lesions. Bring your dog’s medical records if possible, and let the veterinarian know if your pet is on any medications. Fine needle aspiration of the tumors or lesions is usually taken for microscopic examination. Some diagnostic tests may reveal low hemoglobin and iron reserves (anemia), low number of platelets, and increased liver enzymes. Radiography (x-rays), CT scans, MRI, and ultrasound can give the veterinarian an idea of how far the disease has spread.
Treatment of Histiocytosis in Dogs
Your dog’s treatment plan is dependent on which type of histiocytosis is found. No treatment is usually needed for CCH, but the veterinarian will want you to keep checking it and schedule follow up appointments for 3-6 months. The treatment for CH and SH are medications and observation. The treatment for HS is surgery, medications, and hospitalization. MH is fatal within days and euthanasia is usually recommended.
Cutaneous Histiocytosis and Systemic Histiocytosis
Medication may include aggressive steroid therapy, azathioprine, tetracycline, or cyclosporine. The veterinarian will want you to continue to observe the tumor growth and watch for side effects from the medication.
Histiocytic Sarcoma (HS)
Surgery to remove the tumor (amputation, if necessary) is necessary right away to stop the cancer from spreading. Chemotherapy and radiation are sometimes used but once the cancer reaches the vital organs it is usually too late, since it has then progressed into MH, which is untreatable and fatal.
Recovery of Histiocytosis in Dogs
Prognosis for CCH is excellent since it usually resolves on its own. CH and SH are good, but since steroids affect the immune system, you must continue to watch for infections. Even a mild infection can be fatal with a weakened immune system. HS prognosis is fair as long as you have caught it before it spread to the internal organs. However, infections need to be watched for with this type of histiocytosis as well, because steroids are used. The fate of MH is grave and your veterinarian may suggest euthanasia.
Histiocytosis Questions and Advice from Veterinary Professionals
Has Symptoms
My golden has been diagnosed with sh, he has a swollen lymph node under is neck tgat recently has gotten larger in size. He had been acting fine until about a week ago and now he doesn't want to eat for me. He has been taking niacinamide and doxycycline for awhile now and it seem to be maintaining but now I am getting worried that he is getting worse. He also has that rattle to his breathing. Any suggestions on what I should do next.
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If you notice sudden changes or an enlargement of a lymph node it would be best to return to your Veterinarian for reevaluation; both the condition (systemic histiocytosis) and doxycycline may cause a decrease in appetite, again this will be explored by your Veterinarian. Without examining Jaxon, I really cannot give you any more input; your Veterinarian may consider other treatments like steroids or cyclosporine. Regards Dr Callum Turner DVM
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We have a 4 yrs old male Boxer with a Histiocytoma on the edge of his ear, it has been examined and a scrape test has shown malignant cells, his surgery has been scheduled. My question is will we have to wait for biopsy results before his Histiocytosis can be typed?
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Recently I noticed a raised lump on my one year old Boxer’s back. At first I thought maybe she scraped herself on some brush or was bitten by something though I never saw and blood or oozing. It’s now week two and I don’t notice that it’s larger but it’s certainly not smaller either. It’s pink, about the size of the top of a small pinkie finger, and doesn’t appear to cause any pain or itching. It is hard to the touch. We haven’t been to the vet yet, but was wondering if we should be concerned or just watch it for a few more weeks?
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My poor Golden Retriever has suffered with Cutaneous Histiocytosis for 5 years now. Her lesions are severe- I would venture to say a 50 plus on her body-almost everywhere you pet her there is a quarter sized raised pink sore, even one next to her eye. She also is struggling to breathe. The treatment recommended is Niacinamide 1500mg/ Doxycycline Hyclate Flex Tabs 1200mg per day- She is not improving. We are desperate. Thank you for your advice.
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My Sheltie is 5 years old and was diagnosed with Cutaneous Reactive Histiocytosis. He had slight bumps on his chest and back. He has been on on tetracycline/niacinamide for a year and his lesions have disappeared but I noticed his fur is thinner and is getting dry skin. Can the medicine cause this or is it the disease. I would like to take him off the medicine for awhile but afraid his disease will come back. The dermatologist did a thyroid check but that was fine. Any suggestions? I don't want a bald Sheltie.
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Hair loss isn’t a typical symptom of cutaneous reactive histiocytosis or a side effect of tetracycline niacinamide administration; but each dog is different and some dogs may be affected by a condition or treatment differently than another. I cannot tell you specifically why Shadow is losing his hair but it may be due to a secondary condition. Regards Dr Callum Turner DVM
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My dog has cutaneous histrocytosis in her ears. She has had an operation to remove her lesions about a month ago but they have returned. I am taking her to a dermatologist for treatment she made a topical treatment but her ears are still oozing but do not have an odor. Am I doing the right thing. She is also on doxycycline 400 mg, and nyacidimide 1500 mg a day.
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Normally the first course of treatment is surgical removal followed by medical treatment; there are different courses which may be taken with medical treatment with varying success, tetracycline and niacinamide has proved to be positive in one study but not for all dogs in the study. It would be best to discuss your options with your Dermatologist as they will be more aware of treatment for this condition. Regards Dr Callum Turner DVM
www.ncbi.nlm.nih.gov/pubmed/17845621
My Sheltie is 5 years old and was diagnosed with Cutaneous Reactive Histiocytosis. He had slight bumps on his chest and back. He has been on on tetracycline/niacinamide for a year and his lesions have disappeared but I noticed his fur is thinner and is getting dry skin. Can the medicine cause this or is it the disease. I would like to take him off the medicine for awhile but afraid his disease will come back. The dermatologist did a thyroid check but that was fine. Any suggestions? I don't want a bald Sheltie.
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My lurcher is nearly 4 years old and has been diagnosed with a cutaneous histiocytosis on the lower part of his front paw. I've been told that is should disappear on it's own. It's not bothering him much but I have to put a sock on it to stop him licking it. I also wash it after walks with salt water. Is there anything that can be done to manage the condition and speed recovery?
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