Sarcoid Tumor in a Horse

A middle-aged gelding presented to PHD Veterinary services for the removal of a large tumor from the base of the right ear (Figures 1 and 2). Two years prior, a smaller tumor was surgically removed from the same ear. The histological report was consistent with a sarcoid tumor. At the time of the original surgery, several sarcoids were removed from different areas including the pectoral region and groin area. The recurring sarcoids were treated with intra-lesional chemotherapy, cryotherapy, topical medications and systemic herbal remedies. At presentation, a large, lobulated tumor was "hanging" from the base of the right ear. There was mild hemorrhage and evidence of moderate necrosis of the tumor. The gelding was resistant to manipulation of the tumor however gentle palpation of the ear noted that the tumor was NOT attached to the cartilage portion of the ear but only the skin and immediate subcutaneous tissues.

Figure 1

Figure 2

The gelding was rendered unconscious via injectable anesthetics and the tumor was removed through a large incision (Figure 3 and 4). Moderate hemorrhage was encountered confirming that the tumor was highly vascular. The incision was partially closed with sutures and the horse was recovered from anesthesia. Examination of the tumor after removal noted it consisted of 3 individual masses and weighed more than one pound (Figure 5).

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Figure 5

This case represents an extreme example of recurrent sarcoids in a horse. Per the owner, the previous management of the sarcoids were initially effective however in time the tumors returned. The removal or de-bulking of the ear-based tumor will most likely not be sufficient in keeping the sarcoid tumor from removal. Aggressive therapy involving intra-lesional chemotherapy agents and cryotherapy will be employed to keep these tumors from continuing the develop!!

Figure 6

 Fast forward 6 weeks and the surgical wound is in the process of healing nicely (Figure 6), however there are several small sarcoids along the tip of the ear and also within the surgical site that are inflamed and beginning to grow. Follow-up treatment included the injection of cisplatin directly into the small sarcoids. Unlike the initial procedure which was done under anesthesia, the cisplatin injection was performed with sedation and a local "block" of the ear. Two weeks after the cisplatin injection, the small sarcoids along the tip of the ear are shrinking however the sarcoids within the surgical site remain inflamed  (Figure 7).

Figure 7

 Hence, the small sarcoids were treated with cryotherapy and the picture in Figure 8 was approximately 2 weeks post cryotherapy. The initial surgical site is a scar and all of the small sarcoids are regressing nicely. This horse will be monitored very carefully to make sure that any new sarcoid growth is treated aggressively!! This case represents an excellent example of the need for early, aggressive and multi-drug treatment of sarcoids in horses.

Figure 8

Resolved Fibrosarcoma in a horse!

Several months ago I presented a case involving a gelding that presented for lameness and soft tissue swelling along the outside of the right knee (carpus). The gelding was lame at the walk and hesitant to flex the limb at the carpus. Ultrasound exam revealed a well demarcated soft tissue mass (dark tissue inside blue circle) that was centered over the carpus (Figures 1-3). The histopathology report was consistent with a fibrosarcoma.

Figure 1

Because the tumor was located immediately adjacent to the joint capsule of the carpus, surgical removal was considered high risk. As such, the tumor was injected with a chemotherapy agent called Cisplatin via ultrasound guidance. The tumor was injected twice, approximately 30 days apart. There was a moderate reduction in the size of the tumor just 3 weeks after the first injection and the gelding was no longer lame at the walk and was more willing to flex the limb at the carpus.

Figure 2

Figure 3

 The gelding's limb was evaluated 4 weeks after the second Cisplatin treatment. There was no evidence of the fibrosarcoma on the outside of the carpus AND under the skin (Figure 5). The ultrasound exam only noted normal subcutaneous tissue and joint capsule between the ultrasound probe and the carpus. The gelding was sound at the walk, trot, canter and has returned to full work!! The case is a good example of the benefits of intra-lesional injection of tumors that are non-operable with chemotherapy agents. There are several chemotherapy agents available and the procedure can be performed at the barn with ultrasound guidance.

Figure 4

Fibrosarcoma in a horse!

A 14 year old gelding presented for a complaint of recent lameness and swelling of the right knee or carpus. There was no history of trauma but a plumb size swelling was palpated along the outside of the knee. The gelding resented direct pressure over the knee and any manipulation of the knee. When radiographed, there were no significant abnormalities noted with regards to the bones or articular surfaces that make up the carpus. However, a moderate soft tissue swelling was noted along the dorsal (front) and lateral (outside) aspect of the carpus (Blue circles in Figures 3-4). 

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Figure 4

An ultrasound exam was performed on the soft tissue swelling and a hypoechoic (dark) soft tissue structure was identified (Figure 5). This structure appeared well demarcated and was consistent with a mass or tumor which was below the surface of the skin yet outside the joint capsule of the carpus.

Figure 5

When the ultrasound image is flipped into the same projection as the radiograph, the soft tissue mass aligns perfectly with the soft tissue swelling noted on the digital radiograph (Figure 6). The red line corresponds to the middle carpal joint and helps demonstrate how close the tumor is to the joint yet does NOT communicate with the joint.

Figure 6

A core biopsy was taken of the soft tissue mass through a small skin incision directly over the area in question and submitted for analysis.  The histopathology report indicated that the core biopsy was consistent with a fibrosarcoma. This type of tumor is not common in horses and although it does not commonly spread to other regions of the horse, it can be locally destructive and aggressive. As such, it was determined that the immediate course of action was intra-lesional injections of a potent chemotherapy drug. Due to the close proximity with the joint capsule, surgery was considered too risky at this point. The gelding has been treated 1x with a chemotherapy medication and a follow-up exam is expected within 2-3 weeks. To be continued...