Figure 1 (left): Harley's tumor is subtle and could have easily been written off as a lipoma. Figure 2 (right): The HT Vista in action, heating the tissue a few degrees prior to scanning. Photo courtesy Mike Petty I can’t speak for other surgeons, but I suspect we all have a similar dilemma when we look at an unknown lump for surgical removal. Should it be removed with wide and deep margins in case it is malignant? What if it is in an area such as the leg, where a larger incision might mean an incomplete closure without performing a tissue-releasing incision like a Z-plasty? What if it is on the head, where a wide incision might risk injury to a cranial nerve or cause distortion of the animal’s features? Should a punch biopsy be done ahead of time prior to removing it? Maybe a cytology, only to get back ambiguous results because we are only taking a millimeter-wide section for the pathologist to look at? All these choices have consequences for both the patient and owner. For the patient, an incision with unnecessarily wide margins means more pain on recovery, a potential injury to surrounding tissue and nerves, and even delayed healing time. It means additional anesthesia risk if it is done in stages. It means additional fear, anxiety and stress for the additional visits and procedures. For the owner, it also means additional money for a more extensive or additional procedures, as well as the emotional component of having to leave their pets twice for two different procedures. A more accurate approach Figure 3: Harley received a score of 3, giving a good probability of this being a malignancy. At last, there is a tool that we can use to help us make a more informed decision, and it is fast and easy, giving us an answer within minutes. A device called HT Vista uses heat diffusion that recognizes cancerous cells by their unique dynamic heat flow properties. This device screens suspicious lumps and bumps and has a negative predictive value of over 98 percent. The system is designed to err on the side of calling a lump malignant (or “requires further investigation”) so as to not call something that appears marginally malignant, benign. In other words, the system divides the likelihood of a lump, along a scale of one to 10, into either the “requires further investigation” (possibly malignant) or benign category. On the other hand, it is important to note what the HT Vista is limited to: It only looks at cutaneous and subcutaneous lumps. It cannot be used on lymph nodes or internal organs. It cannot accurately predict malignancy in a cutaneous lump that has a raw or bleeding surface. If there is a negative result, there is a 98 percent likelihood the scanned mass is not malignant. Questionable results will always put the score on the malignant or “suspicious” side, so that a potential malignancy is not ignored. How it works Figure 4: Fluff’s growth prior to scanning and removal. The machine must be turned on with an internet connection. An area on the patient is clipped close with a number 40 blade, including some adjacent “normal” tissue. The device is then placed over the lump and some of the normal tissue next to it, and then the tissue is mildly heated for a few seconds. It then scans the tissue to see how it reacts—malignant tissue reacts differently to thermal stimulation than normal tissue does, and the device AI algorithm interprets the heat diffusivity of selected adjacent areas. The whole process takes one minute, with results returned within minutes. A decision can then be made—removal with wide margins, narrow margins, no removal at all, or further follow up needed. Cases in point Figure 5: One week post-surgery prior to suture removal. The following are three cases that I saw in my clinic, along with scores and histopathology/cytology outcomes. Case 1: Harley, an eight-year-old neutered male American pit bull, was presented with a rapidly growing subcutaneous lump on his lateral thigh. Upon presentation it seemed fairly innocuous. However, it was large enough there was a concern for complete closure should we have to do wide margins (Figure 1). Next, we scanned the growth (Figure 2). A few minutes later, we got back the report (Figure 3). Due to a score of 3, I removed the growth with 4-cm wide margins and as deep as I could down to the muscle layer. Thanks to this information, the report came back as a soft tissue sarcoma, grade 2, with clean margins. Case 2: Fluff is a 13-year-old neutered male Canaan dog that was presented with a lump on his thorax that had been the same size for many months but was suddenly growing (Figure 4). The owner was reluctant to have it removed because several years previously, we had removed a lump from Fluff that was then diagnosed as a mast cell tumor with inadequate surgical margins. At the time of the surgery, it appeared to be a lipoma upon removal, and narrow surgical margins were made. The surgery site subsequently dehisced, and it required multiple surgeries before it was healed. Figure 6: The owner was very concerned this might be a tumor. I was concerned about the location on the shoulder and post-surgical complications. Understandably, the owner did not want to put his now aged dog through that scenario again. Fortunately, we now had the HT Vista and were able to determine it was a malignant growth, so it was removed with wide and deep margins (Figure 5). Once again, we got back a histopathology report of soft tissue sarcoma grade 1, clean margins. Case 3: Remington is a six-year-old neutered male Weimaraner that was presented with a lump just cranial to his scapulohumeral joint, which had recently changed in character from soft and fluctuant to firm (Figure 6). The owner was interested in having it removed, but I explained there would be a healing issue because of its proximity to the shoulder joint and the fact Remington was a very athletic and active dog. She agreed to have it scanned with the HT Vista, and it came back with a low likelihood of malignancy with a score of 8 (Figure 7). For the purposes of this article, we did a cytology on multiple locations to confirm the score and got nothing back but adipose cells. Remington was discharged from the clinic without having to undergo general anesthesia and an unnecessary surgical procedure. There are 14.5 million growths detected every year in the U.S. Approximately 40 percent of them are never diagnosed for reasons of time, cost, and invasiveness of procedure among others. As a surgeon, I now have a tool that is noninvasive, unpainful, quick, and easy to use, that will give me and the concerned client a window into what the next step should be. I have only had this device for several months and already I cannot imagine practicing without it. Figure 7: It got a green rating, meaning most likely benign. Michael Petty, DVM, is a graduate of the veterinary school at Michigan State University. As the owner of Arbor Pointe Veterinary Hospital and the Animal Pain Center in Canton, Michigan, he has devoted his professional life to the care and well-being of animals, especially in the area of pain management. Dr. Petty is the past president of the International Veterinary Academy of Pain Management. A frequent speaker and consultant, he has published articles in veterinary journals and serves in an advisory capacity to several pharmaceutical companies on topics of pain management. Petty has been the investigator/veterinarian in 12 FDA pilot and pivotal studies for pain management products. He has lectured both nationally and internationally on pain management topics.
