犬のまれな形質細胞腫を理解する

執筆者 TCMVET | 2024年9月19日 | 犬の癌と腫瘍

Plasmacytomas are rare tumors in dogs that originate from plasma cells, a type of white blood cell responsible for producing antibodies. While plasmacytomas are uncommon, they can be a serious condition that requires prompt veterinary care. In this article, we’ll explore what plasmacytomas are, their symptoms, how they’re diagnosed, and the treatment options available to help your dog recover.

What Are Plasmacytomas in Dogs?

Plasmacytomas are tumors formed from plasma cells, often appearing in various parts of a dog’s body, including the skin, gastrointestinal tract, or oral cavity. Most plasmacytomas are benign (non-cancerous), but in some cases, they can be malignant and spread to other areas of the body, such as bones or internal organs.

There are two main types of plasmacytomas seen in dogs:

1. Cutaneous Plasmacytomas: These occur on the skin and are the most common type of plasmacytoma in dogs. They typically present as solitary masses on the limbs, head, or trunk.
2. Extramedullary Plasmacytomas: These develop outside the bone marrow, most often in mucous membranes, such as the mouth, stomach, or intestines.

Symptoms of Plasmacytomas in Dogs

Plasmacytomas may not cause noticeable symptoms in the early stages, but as the tumor grows, signs can become more apparent. The symptoms your dog displays will vary depending on the location of the plasmacytoma:

• Cutaneous Plasmacytomas: These are usually small, raised, firm, and solitary lumps found on the skin. The lumps may be red, ulcerated, or cause mild irritation, but are often painless.
• Oral or Gastrointestinal Plasmacytomas: Dogs with plasmacytomas in the mouth or digestive tract may exhibit symptoms such as:
  • 食べることや飲み込むことが難しい
  • 嘔吐
  • Diarrhea or bloody stools
  • 体重減少
  • Bad breath (halitosis)
• 全身症状: If the plasmacytoma is malignant and spreads, your dog may experience more general signs of illness, such as fatigue, loss of appetite, or unexplained weight loss.

原因と危険因子

The exact cause of plasmacytomas in dogs is not well understood, but there are certain risk factors and breeds that appear to be more prone to developing these tumors:

• 品種の素因: Older dogs and breeds such as Cocker Spaniels, Golden Retrievers, and Scottish Terriers are more likely to develop plasmacytomas.
• 年齢: Plasmacytomas are most commonly seen in middle-aged to senior dogs, though they can occur in younger animals as well.

Diagnosing Plasmacytomas in Dogs

If you notice a lump on your dog’s skin or your dog is experiencing symptoms that suggest a plasmacytoma, a visit to the veterinarian is essential for proper diagnosis. The diagnostic process typically includes:

1. 身体検査: Your vet will perform a thorough physical examination, particularly inspecting any lumps or masses for size, shape, and texture.
2. Fine-needle aspiration (FNA): A small needle is inserted into the lump to collect cells for analysis. This is a quick and minimally invasive way to evaluate the type of tumor.
3. 生検: In some cases, a surgical biopsy may be necessary to remove a larger sample of the tumor tissue for more detailed examination.
4. 画像検査: If there is concern that the plasmacytoma has spread internally, your vet may recommend X-rays, ultrasound, or MRI scans to check for tumors in other parts of the body.
5. Blood work: Blood tests may be conducted to assess the overall health of your dog and to look for any signs that the tumor is affecting internal organs.

Treatment Options for Plasmacytomas in Dogs

The treatment approach for plasmacytomas depends on the size, location, and whether the tumor is benign or malignant. Common treatment options include:

1. 外科的除去: Surgery is the most common treatment for cutaneous plasmacytomas. Since these tumors are usually benign, complete surgical excision typically results in a full recovery. In cases of oral or gastrointestinal plasmacytomas, surgery may also be necessary to remove the tumor.
2. 放射線治療: If the plasmacytoma is inoperable or if surgical margins are incomplete, radiation therapy may be used to shrink the tumor or prevent its regrowth.
3. 化学療法: Chemotherapy is generally reserved for cases where the plasmacytoma is malignant and has spread to other areas of the body. Chemotherapy can help control the spread of cancerous cells and improve quality of life.
4. モニタリング: For benign plasmacytomas that are not causing any symptoms or discomfort, your vet may suggest a wait-and-see approach, monitoring the tumor for any signs of growth or changes.

Prognosis for Dogs with Plasmacytomas

The prognosis for dogs with plasmacytomas largely depends on whether the tumor is benign or malignant. Dogs with benign cutaneous plasmacytomas that are surgically removed have an excellent prognosis, with most making a full recovery.

However, if the plasmacytoma is malignant or has spread to other parts of the body, the prognosis may be more guarded, and long-term management may be necessary.

Plasmacytomas are rare tumors in dogs, but they can be successfully managed with early diagnosis and appropriate treatment. If you notice any unusual lumps or signs of illness in your dog, prompt veterinary care is crucial. With timely intervention, many dogs with plasmacytomas go on to live healthy, happy lives.