Oreo's lab results: nerve sheath tumor

Today I got the results from Oreo's biopsy (she had a lump removed from her front leg last Thurs.). The lump is a nerve sheath tumor, which the vet said is benign but can recur locally. She said the margins of the biopsy were "close," and they couldn't call them clear. So all this means that there is a low to medium chance that the tumor will grow back in the same location, but it will not spread to other parts of her body.

This is mixed news: not perfect, but at least it's not cancer. I have to decide if I want to (1) have more surgery now to take a larger margin that will be sure to get all of the tumor out, or (2) wait and watch for regrowth, and then have the sugery if necessary. I'd go ahead with the first, but the surgery would be pretty serious and involve removing some muscle (vet said it would be very painful for about 10 days).

So, I have some research to do and a decision to make. If anyone has any info. on nerve sheath tumors or surgery involving removing muscle from the skinny front leg, please let me know. Thanks for your continued prayers,

Andrea

I hope this site canoffer you some more insight??





SouthPaws Veterinary Referral Center
6136 Brandon Avenue
Springfield, Virginia 22150
Tel: (703) 569-0300
Fax: (703) 866-4962


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Summer/Fall 1998 Newsletter
Peripheral Nerve Sheath Tumors
Dan Brehm, VMD (Surgery)
Betsy Dayrell-Hart, DVM (Neurology)

One of the more difficult diagnostic challenges you can face in veterinary practice is the peripheral nerve sheath tumor (PNST). These tumors are derived from the cells surrounding the axons of peripheral nerves. They have been known by a variety of names, including neurofibromas, neurofibrosarcomas, and schwannomas, but are now referred to as PNST due to their presumed common cell of origin (the Schwann cell).

What makes PNSTs so much of a diagnostic challenge is the similarity of their presenting clinical signs to many other, more common, orthopaedic disorders. The most common clinical sign associated with PNST is chronic, progressive, unilateral forelimb lameness. In a 1995 study of 51 cases of PNST, 78.4% of dogs presented with this sign. This tumor is typically seen in older dogs (average age was 8.7 years), but has been seen in dogs as young as 3 years. Because this tumor is usually seen in older dogs, it is very common to misinterpret it as elbow or shoulder arthritis, two conditions also commonly seen in older dogs. Pain on palpation near the tumor site was seen in 48.7% of dogs. Since most of these tumors grown in the axillary region, it is again common to mistake the pain as derived from the shoulder. Only 37% of dogs had a palpable mass (these are typically found only on deep palpation of the axillary region, which sometimes requires sedation for efficient palpation). One sign that is commonly seen with PNST and less commonly seen with chronic arthritis is muscle atrophy. About 93% of dogs with PNST had moderate to severe muscle atrophy of the affected limb.

Diagnosis of PNST often requires multiple tools. The first step is to take radiographs to look for obvious orthopaedic abnormalities, such as fractures or bone tumors. If the radiographs do not fit the clinical picture, we recommend electromyography (EMG). In the 1995 study, 100% of cases in which an EMG was performed demonstrated abnormal, spontaneous electrical activity, indicative of neurological compromise to the muscles of the affected limb. Electromyography is not specific for PNST, but is is a sensitive test to help differentiate between denervation and disuse muscle atrophy (usually associated with neurological and orthopaedic causes of lameness, respectively). If an EMG is abnormal, additional tests are necessary to help better define the nature and scope of the probably tumor. Myelography can be very useful to identify extension of the tumor into the spinal canal At SouthPaws, we have been utilizing MR imaging more frequently when dealing with PNST. This test costs about the same as a myelogram, and has been very good at demonstrating both intra-spinal extension of PNSTs as well as better defining the peripheral limits of the tumor. We have been very excited about the results from MR scans and about the benefits they provide when planning the surgical approaches used to resect the tumor. The best hope we have to successfully treat PNSTs is early, accurate diagnosis, which electromyography and magnetic resonance imaging can assist in providing. Both electromyography and magnetic resonance imaging (as well as myelography) are available through the SouthPaws neurology service.

SouthPaws has an active and interactive oncology unit, combining medical and surgical oncology services, which allows a multi-disciplinary approach to the cancer patient. It is very common to have many of the services at SouthPaws participate in the diagnosis and treatment of our cancer patients. We view this approach as vital to providing the best care possible. Our goal has always been to provide our cancer patients - as well as all of our other patients - with as long and good a quality of life as can be achieved. SouthPaws has a strong and experienced oncology team; we are, as always, ready and willing to help referring veterinarians and their patients in any way we can.

15% of all skin /subcutaneous tumors
STS of the trunk and extremities are very invasive into surrounding tissue with a generally low metastatic rate
Malignant peripheral nerve sheath tumor is most common soft tissue sarcoma
Complete, wide surgical resection, confirmed histologically, is highly predictive of local tumor cure
These tumors are not encapsulated but have a "pseudocapsule" comprised of compressed tumor cells
40%-70% of grade 3 tumors will metastasize "Soft tissue sarcomas (STS) make up a large category of tumors that arise from connective tissue. This category includes tumors of fibrous tissue, fat, smooth muscle, nerves, and lymphatic vessels. Histologic diagnoses include fibrosarcoma, MPNST, malignant fibrous histiocytoma, myxosarcoma, liposarcoma, lymphangiosarcoma and undifferentiated sarcoma. The most common STS in dogs is the malignant peripheral nerve sheath tumor. Tumors such as hemangiosarcoma, osteosarcoma, chondrosarcoma, rhabdomyosarcoma and synovial cell sarcoma are often classified as soft tissue sarcomas. However, their behavior is not consistent with that of the more common STS and they are therefore considered separately in veterinary medicine."
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tumors of the skim
"Approximately 20 to 30% of primary tumors of the skin and subcutaneous tissues are histologically malignant in the dog, compared to 50 to 65% in the cat." This site EXCELLENT FOR CATS
GENERAL fact sheet for soft tissue sarcomas
Soft tissue sarcomas (STS) are tumours arising from connective tissue (mesenchyme other than bone) in middle aged to old dogs. They comprise about 15% of all skin tumours, and about 1% of all malignancies. The most common histological types of STS are fibrosarcomas, haemangiopericytomas, neurofibrosarcomas, schwanomas (also called malignant peripheral nerve sheath tumors), and malignant fibrous histiocytomas. Excluded in this group are tumours of haematopoietic or lymphoid origin and haemangiosarcomas. Despite the different histological types, STS share similar characteristics:

arise from any anatomic site in the body
locally invasive
recur after conservative excision
low metastatic rate
poorly responsive to radiation therapy
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SOFT TISSUE SARCOMAS IN DOGS AND CATS
" What exactly do we mean when we make a diagnosis of soft tissue sarcoma? This includes a group of sarcomas including fibrosarcoma, peripheral nerve sheath tumors (schwannoma or neurofibrosarcoma), "hemangiopericytoma," malignant fibrous histiocytoma, myxosarcoma, and liposarcoma. With the possible exception of liposarcoma, the exact tumor type is less important than the grade of tumor. In fact, at the light microscope level, it is difficult to distinguish between schwannoma and neurofibrosarcoma, and hemangiopericytomas are likely a form of peripheral nerve tumor. The grading system we use is adopted from human medicine and comprises three grades -- 1 being the least malignant and 3 being the most malignant. Grade is based on overall tumor differentiation, mitotic rate, and amount of tumor necrosis. In a recent study of dogs with soft tissue sarcomas treated by aggressive surgery alone, grade was predictive of survival as the 3-year survival rate was about 80% for grade 1, 50% for grade 2, and 20% for dogs with grade 3 tumors (JAVMA 211; 1997, p. 1147). Grade also was predictive of tumor recurrence in soft tissue sarcomas treated with surgery and adjuvant radiation therapy.
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Hemangiosarcoma,Hemangiopericytomas and Hemangiomas
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Sending Oreo lots of hugs and kisses.
Please keep us posted.

Thank you, Lorraine O, for all of that information. It was interesting to read.

Thanks, KYS--I'll pass the hugs and kisses on to Oreo.

That's so good that it isn't malignant. Keep us posted on how Oreo does, OK?

Awww Oreo. :( *hugs* Sending lots of love to you.

Oh, sweet Oreo:( The great news is that it's not malignant! You have a lot of info. to work with and a lot to consider. Whatever gets Oreo healthy and whole again as soon as possible, is my wish. Lots and lots of hugs and kisses to your Oreo:) And hugs for your mommy:) Please keep us upadted on Oreo and your decision. Sandra

Glad the tumor is benign. Good luck on the decision making. Hugs.

If the Vet believes the margins may not have been clean, then you can try 2-3 courses of radiation at the site in an attempt to clean up the stray cancer cells.

I talked to a second, more experienced, vet today. It looks like this tumor is a kind of cancer after all, just not what we normally think of because it doesn't travel through the blood and metastisize to other locations. (The lack of spreading is what the first vet meant by "benign," but that term wasn't clear to me.) So we will need to wait for her biopsy location to heal for 30 days and then do the extra surgery to get clear margins.

I asked about radiation: he said that compared to the surgery, radiation would cause Oreo more physical and mental stress and be less effective.

Thanks for listening, and I'll let you know how she does in a month.

Oh:(:(:( I'm glad though that you were able to get a more complete picture of Oreo's condition in order to treat it properly. It does sound as though it is the type of tumor that will respond well to surgery. Please keep us updated on Oreo's surgery date. Lots and lots of hugs to you dear Oreo. Our hearts and prayers are with you and your mom. Love, Sandra