Removal of benign soft tissue tumors in the dog utilizing a flexible fiber CO₂ laser

By David Duclos, DVM, DACVD For The Education Center
Originally Published In Veterinary Practice News, December 2017 – Download as a PDF

Meibomian adenoma is a benign, often age-related tumor that arises from the meibomian (tarsal) gland. It results from the accumulation of glandular material (sebum). Eyelid masses can cause discomfort, irritation to the cornea, and conjunctiva, and can interfere with the eyelid function.

Fibroadnexal hamartoma (also referred to as fibroadnexal dysplasia or focal adnexal hyperplasia) is a benign, typically solitary lesion, exophytic, firm and well circumscribed, with a smooth surface. It was found to be the most common lesion in the dog. These lesions occur in large-breed dogs, most often on the distal extremities around pressure points and interdigital spaces. The patient described in this study had lesions on the neck and body.

Opinions differ on the etiology of fibroadnexal hamartomas. Some authors think they result from a response to a trauma;^[1] others think they may originate as a primary malformation of follicular structures.^[2]

Patient

Patient, an 11-year-old male, neutered Siberian husky dog, was brought to the clinic with a tumor on his left upper eyelid margin (Figure 1) and three small circumscribed nodular tumors on the body (Figure 2). None of the tumors were inflamed. The tumor on the eyelid irritated cornea and the surgeon recommended to have it removed. The tumors on the body were asymptomatic, but the owner wanted them removed for cosmetic reasons.

Procedure preparation

The patient was positioned in lateral recumbency. Anesthesia was induced with Propofol 3 mg/kg IV and maintained with isoflurane via endotracheal tube. Hair around the three tumors on the neck and body was clipped.

Laser equipment and settings

The flexible fiber CO₂ laser was utilized equipped with the tipless adjustable focal spot size handpiece (VetScalpel^® by Aesculight, Bothell, Wash.).

Settings for Meibomian adenoma: The handpiece was set to the 0.8-mm laser focal spot size (Figure 3).

Tumor ablation: 4 watts SuperPulse (SP) repeat mode, in the Medium group M2-4, at 10 Hz—this is a total of 800 milliwatts of average power delivered to the target tissue (Figure 4).

Tumor bed ablation/caramelization: For the tumor bed ablation, with one press of a button, the average power was decreased to 400 milliwatts.

Settings for fibroadnexal hamartomas (FHs): The handpiece was adjusted to the 0.25-mm laser focal spot size.

Initial incision: 20 watts SuperPulse (SP) repeat mode, in the Fast group F2-5, at 29 Hz, this is a total of 14500 milliwatts, or 14.5 watts, of average power delivered to the target tissue (Figure 5).

Resection: 12 watts SuperPulse (SP) repeat mode, in the Fast group F2-5, at 29 Hz – this is a total of 8700 milliwatts, or 8.7 watts, of average power delivered to the target tissue.

Laser procedures

Meibomian adenoma was removed first. The cornea was protected with saline-soaked gauze; a saline moistened cotton swab was used as a backstop (Figure 6-A). The eyelid was grasped with a tissue forceps (the tumor may be isolated using chalazion eye forceps). For this procedure, the tumor tissue was incised around the margin (Figure 6-B). The surgical area was wiped with a saline moistened cotton swab to remove any traces of char. Laser ablation was continued, as needed, until the mass was removed (Figure 6-C). It is important to wipe the char in between laser passes to ensure the most efficient penetration of laser energy. After the mass was ablated, the power was reduced and the tumor bed was “painted” with the laser in order to eliminate the final cell layer, sculpt the wound edges, and “caramelize” the site (Figure 6-D). Sutures were not needed.

The three small tumors on the patient’s neck and body were removed via laser excision. First, the tumor was grasped with the Adson thumb forceps and circumscribed with the laser along the visible junction line with the normal tissue (Figure 7-A). Then the laser power was decreased and the initial incision was deepened with a few laser passes; the tumor was retracted, and then completely undermined (Figure 7-B) and removed. The remaining surgical defect was wiped with a saline soaked sponge (Figure 7-C) and closed using interrupted cruciate suture pattern. The remaining two tumors were removed using the same technique.

The excised specimens were submitted for histopathology examination. The results revealed dermal fibrosis and adnexal hyperplasia, with no evidence of viral cytopathology or exogenous foreign bodies.

Postoperative care

The patient was administered atipamezole 250 mcg/kg and butorphanol 0.2 mg/kg at surgical recovery. An Elizabethan collar was applied to prevent self-mutilation. The patient was discharged home later the same day and the owners were instructed to give him carprofen 12.5 mg by mouth twice a day for five days. For the eyelid, an ophthalmic antibiotic ointment was recommended twice a day for five days to encourage clean re-epithelialization.

Sutures were removed 11 days after the surgery. Healing was uneventful, and the patient is doing very well. For the eye, no corneal irritation was noted, and the eyelid was healing well.

Conclusion

The CO₂ laser provides the surgeon with the superior ability to control the fluence by easily changing spot sizes, power settings and to switch between continuous wave to SuperPulse modes; because of this the surgeon has excellent control to remove abnormal tissue and to avoid unnecessary damage to healthy adjacent structures. This laser benefit is especially prominent in delicate areas, such as eyelids. Furthermore, because the CO₂ laser coagulates small vasculature (less than 0.5 mm in diameter) as it cuts, the surgeon has greater control due to better visibility in a bloodless surgical field.

Dr. Duclos is a small-animal practitioner in Lynnwood, Wash., where he is the owner and clinical dermatologist at the Animal Skin & Allergy Clinic. He completed his residency in veterinary dermatology at the University of Pennsylvania. He is an associate clinical instructor for the Western University College of Veterinary Medicine in Pomona, Calif., and teaches senior veterinary students as externs at his clinic. He frequently hosts veterinary students from other Veterinary Medical Colleges around the US, and from veterinary colleges in Europe who are seeking to learn about the specialty of veterinary dermatology during their third and fourth year of veterinary school. In addition, Dr. Duclos teaches veterinary residents in dermatology who are seeking to learn more about laser surgery for two- to four-week externships sponsored by the American College of Veterinary Dermatology. He recently has begun to take part in the One Health initiative, recognizing that the health of people is connected to the health of animals and the environment. The goal of One Health is to encourage the collaborative efforts of multiple disciplines working locally, nationally, and globally to achieve the best health for people, animals, and our environment. He authored a number of book chapters and scientific papers on various subjects in veterinary dermatology. He extensively lectures in the US, Canada, and Europe. Dr. Duclos is well known in the veterinary dermatology specialty for his expertise in CO₂ laser surgery and for his interest in clinical photography.

References

1. Goldschmidt MH, Shofer FS. Skin tumors of the dog and cat. 3rd ed. Oxford, UK: Pergamon Press, 1992.
2. Loures FH, Conceição LG. “Nevi and cutaneous hamar tomas in dogs: retrospective clinical and epidemiologic study of 81 cases.” Cienc Rural, Santa Maria. 2009;39(9): 2527-32

This Education Center article was underwritten by Aesculight of Bothell, Wash., the manufacturer of the only American-made CO₂ laser.