Blood in a dog's fine needle aspirate may seem like something not much unusual to the average Joe, but it must be remembered that it's not a vein or just skin that is being punctured, but rather in most cases, a lump or lymph node which often contain different matter. In order to better understand what blood in a dog's final needle aspirate really means, it helps to first understand how needle aspirates work and what's expected to generally be found in lumps and bumps.
How Fine Needle Aspirates Work
If your dog has any suspicious lump or bump, it's always a good idea to play it safe and have it aspirated. Veterinarians will aspirate lumps and bumps using a procedure known as fine needle aspiration.
As the name implies, a very thin needle (typically a 22 gauge needle) is used to poke the lump in several areas and draw up any fluid found.
The purpose of poking several areas is to up the chances of getting a variety of samples considering that lumps aren't necessarily homogeneous (the same throughout).
For sake of comparison, imagine sucking up material from an apple pie covered with a tea towel using a straw. Next, you place the sucked up material on a plate. Chances are, you may end up with crust, apples or just sauce. If you see apples, you will correctly guess that an apple pie was hiding under the tea towel. If you get crust or sauce instead you may not know what type of pie you are dealing with. Same happens with fine needle aspirations.
So after material is aspirated from a lump, it is placed onto glass slides and "stained" with dye to see the various components of the sample. These slides are then checked under a microscope, an evaluation known as"cytology" which entails evaluating the individual cells.
Most vets can evaluate these cells under a microscope, however, a definitive diagnosis can be obtained by sending the slides to a pathologist, a specialist who has made of examining laboratory samples his area of specialty.
In many cases, lumps are often innocent collections of fat known as lipomas. However, there are many other possible types of lumps diagnosed with fine needle aspiration and these may include lymphosarcomas, lymphomas, mast cell tumors, histiocytomas and cysts.
What Does Blood in a Dog's Fine Needle Aspirate Mean?
Blood in a dog's fine needle aspirate can mean several things. Sometimes, it could just mean that the fine needle aspirate is non-diagnostic. When this happens it's referred to as "blood contamination." It is possible that certain tumors may not exfoliate or shed cells into their surroundings and the vet may therefore fail to get anything worthy of investigating.
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For example, it may simply happen that the fine-needle aspirate has "suck up" blood found within or around a cancerous mass while missing the cancer cells themselves. In such a case, sending a non-diagnostic slide to a pathologist is a waste of time and a waste of the dog owner's money.
Options at this point may be to keep trying to retrieve several samples in hopes that some cellular material can be retrieved, or a tissue biopsy may be recommended so to remove a more substantial piece of tissue for a full diagnosis. This would require general anesthesia.
In some cases though, aspirating blood from a mass may be indicative of hematomas and certain benign and malignant forms of cancers.
Hematomas in Dogs
In young active dogs, hematomas are a possible cause for blood in a dog's fine needle aspirate. Hematomas are basically bruises that often occur as a result of some type of trauma due to the dog being hyper and running around. In older dogs, hematomas may occur too, but more likely than not, they occur as a result of being more wobbly and falling.
Hematomas are simply collections of blood that occur as a result of injury to the wall of a blood vessel. With the blood vessel wall injured, blood seeps out into the surrounding tissues forming a pocket of blood.
Hematomas improve with anti-inflammatories and locally applied warm compresses can help reduce their size. In a dog with no history of trauma, then the collection of blood in a fine needle aspirate may be suggestive of tumors. The tumors may be benign or malignant.
Malignant Hemangiosarcomas (HSA) in Dogs
It's unfortunate, but in older dogs, there are chances that blood in a dog's fine needle aspirate may be suggestive of the presence of a type of cancerous mass known as a hemangiosarcoma. Here's a fact: with dermal (skin) hemangiosarcomas, it is difficult to get an accurate needle aspirate and partial biopsy results. It may therefore be preferable to send an entire mass off to the lab for a definite diagnosis.
Hemangiosarcomas are malignant cancers that tend to spread to other body parts (lungs, heart). They are masses that originate from a blood vessel wall making them highly vascular and therefore prone to growing rapidly. In some cases, this cancer may reach subcutaneous tissue and even the bone.
In this case, it's important to conduct several other tests such as chest-x-rays and ultrasounds to check for signs of the cancer spreading to other organs. These tests can evaluate whether the cancer has spread internally and may therefore help dictate the course of action.
"Fine-needle aspiration and impression smears are of limited value in diagnosing HSA because the blood collected is typical of hemorrhage and neoplastic endothelial cells are not readily found. Histopathology should be performed for a definitive diagnosis"~Diya Sharma
Benign Hemangiomas in Dogs
Hemangiomas are the benign versions of hemangiosarcomas. Hemangiomas and hemangiosarcomas can be readily distinguished from one another once a biopsy is sent out for histopathology. Hemangiomas tend to have a more uniformed appearance and a typical, organized architecture. Unlike hemangiosarcomas, hemangiomas are often curable with complete surgical removal of the mass.