Use of a carbon dioxide laser for surgical management of cutaneous masses in horses: 32 cases (1993-2000)

Treatment of equine sarcoids: A systematic review

BACKGROUND

The sarcoid is the most common equine cutaneous neoplasm. Evidence-based treatment of this condition is often lacking, and selection of treatment modality based on clinical experience or anecdotal evidence.

OBJECTIVES

To assess the quality of the currently available best evidence regarding the treatment of the equine sarcoid.

STUDY DESIGN

Systematic review.

METHODS

In compliance with PRISMA guidelines, literature searches were performed in PUBMED, Web of Science, CAB Abstracts, EMBASE (Ovid) and Scopus in April 2021. Included papers were required to describe an interventional study examining sarcoid treatment strategy, of level 4 evidence or greater. The case definition required confirmation of at least some included lesions on histopathology, and a minimum of 6 months of follow-up was required on treated cases. Studies were assessed by two independent reviewers (KO, CD). Data extraction was performed manually, followed by risk of bias assessment. Methodological quality was assessed using the GRADE system.

RESULTS

In total, 10 studies were included in the review. Case definition was confirmed via histopathology in all included lesions in 60% of papers. Time to follow-up was variably reported. Overall risk of bias ranged from 'some concerns' to 'critical'. Reported sarcoid regression rate ranged from 28% to 100% on an individual sarcoid level, and 9%-100% on a whole horse level. Transient local inflammation was reported following most treatment strategies, with further adverse events reported infrequently.

MAIN LIMITATIONS

Review methodology excluded a large proportion of available literature regarding the equine sarcoid. Significant heterogeneity between included studies prevented quantitative synthesis and most included papers were at significant risk of bias, indirectness, and imprecision.

CONCLUSIONS

There is insufficient evidence currently available to recommend one sarcoid treatment over another. There is an urgent need for sufficiently powered, randomised, placebo-controlled trials in order to allow more definitive comparison of the efficacy of different treatment strategies.

Equine Melanocytic Tumors: A Narrative Review

Adult grey horses have a high incidence of melanocytic tumors. This article narratively reviews the role of some genetic features related to melanoma formation in horses, such as STX17 mutation, ASIP or MITF alterations, and the link between the graying process and the development of these tumors. A clear system of clinical and pathological classification of melanocytic tumors in naevus, dermal melanoma, dermal melanomatosis and anaplastic malignant melanoma is provided. Clinical and laboratorial methods of diagnosing are listed, with fine needle aspiration and histopathology being the most relevant. Relevance is given to immunohistochemistry, describing potentially important diagnostic biomarkers such as RACK1 and PNL2. Different therapeutical options available for equine practitioners are mentioned, with surgery, chemotherapy and electroporation being the most common. This article also elucidatesnew fields of research, perspectives, and new therapeutic targets, such as CD47, PD-1 and COX-2 biomarkers.

Management of equine sarcoids

Sarcoids are the most common cutaneous neoplasm of the horse, arising as a result of a neoplastic proliferation of fibroblasts associated with infection with bovine papillomavirus, most notably types 1 and 2. Although they do not metastasise, they are locally invasive and aggressive, and can lead to important welfare concerns, interfere with tack and therefore impede athleticism, and undoubtedly lead to a reduction in the value of affected horses. This review discusses the evidence behind the most commonly used treatments for equine sarcoids. The most commonly used treatments are discussed. No one treatment is universally successful, and there are many treatments with varying level of scientific evaluation and reported success rates.

Interventions for treatment of cutaneous melanoma in horses: a structured literature review

Several therapies have been developed to treat equine cutaneous melanoma, but formal comparisons among different treatment options are currently unavailable. It was our intent to assess the efficacy of different treatment protocols and the quality of the studies based on the original published data, and summarize the knowledge concerning the outcome after equine cutaneous melanoma management. This structured review followed PRISMA procedure to search for treatment protocols on equine cutaneous melanoma published from 1960 until June 2021. Studies were assessed for the risk of bias. A descriptive analysis was performed, considering the disease control rate, the recurrence rate of the tumor, comorbidities, need for anesthesia, and horses' welfare. Twenty-three studies were included, from which the treatment outcomes of 173 horses were assessed. The homogeneity of the included trials was low. The percentages of each treatment arm achieving a partial response and curative effects accounted for 93.1% (surgical intervention), 90% (medication), and 39.4% (immunotherapies), respectively. A variable efficacy of different therapies of equine cutaneous melanoma was observed. Surgical intervention performed the best from the perspective of local antitumor effects alone. This literature review and descriptive analysis can serve as a source to assist in designing quality therapy research and can potentially aid in providing a clinical treatment reference for equine cutaneous melanoma.

Electrochemotherapy for the treatment of cutaneous solid tumors in equids: A retrospective study

Background

Electrochemotherapy (ECT) promotes the increased uptake of antitumor agents through the administration of permeabilizing electric pulses, thus enhancing chemotherapy effectiveness.

Aim

Our study aimed to describe the tolerability and efficacy of ECT alone or in association with surgery to manage solid neoplasms in equids.

Methods

Medical records of equids with a diagnosis of malignant tumors treated with ECT alone or in combination with surgery were retrospectively evaluated. Each equid received local treatment within the tumors or the tumors' bed with cisplatin at the dose of 0.5 mg/cm². Trains of permeabilizing biphasic electric pulses were then applied under spinal or general anesthesia.

Results

Sixteen equids were enrolled in this study. There were nine melanoma cases, four fibrosarcoma, and three squamous cell carcinoma. Of those 16 equids, 7 received ECT for treatment of intraoperative local disease, while in 9 cases, ECT was the only treatment modality. The seven equids treated with the combination of ECT and surgery still have no evidence of disease at different times ranging from 9 to 60 months. The remaining nine had the following responses: two complete remissions, five partial responses, one stable disease, and one progressive disease. The treatment was well-tolerated, and local side effects were minimal. No systemic effects were documented.

Conclusion

This retrospective study suggests that ECT may be beneficial for equids with solid neoplasms and could be a useful addition to the current therapeutic options considering its low cost, limited toxicity, and ease of administration.

Surgical excision of a malignant metastatic melanoma located in a skeletal muscle of the lateral thorax of a horse

BACKGROUND

A 20-year-old grey Warmblood gelding that had history of dermal melanomatosis.

OBJECTIVE

To report surgical treatment of a 6-cm large malignant metastatic melanoma located in the cutaneous trunci muscle of the left lateral thorax of a horse.

METHODS

A 20-year-old grey Warmblood gelding was referred for evaluation of a large, rapidly growing, thoracic mass. Clinical examination revealed an ovoid, firm, non-painful, movable mass, approximately 6 cm in diameter, located in the cutaneous trunci muscle of the left lateral thorax. Multiple melanocytic nodules were also found at the perianal region and ventral tail. Rectal examination, ultrasonography and endoscopy of the respiratory tract revealed no melanomas internally. Haematological and biochemical values were within normal limits. Surgical excision of both the thoracic mass and perianal nodules was the treatment of choice. Histopathology of the distant thoracic mass confirmed the diagnosis of malignant metastatic melanoma secondary to the perineal lesions that were confirmed as dermal melanomatosis.

RESULTS

The horse recovered uneventfully. Up until 3 years post surgery there was no tumour regrowth at the excision sites.

CONCLUSION

Surgical excision of the metastatic melanoma was performed and considered successful, with no gross evidence of tumour reoccurrence. Despite the fact that surgical excision is considered a treatment option regarding equine dermal melanomatosis, there is no previously published study proposing surgical removal of distant malignant metastatic melanocytic masses. This is the first report of a successful surgical excision of a large (6 cm) metastatic melanocytic tumour from the skeletal muscle of the lateral thorax of a horse.

En-bloc Auriculectomy for Removal of a Large Pinna-Based Ear Mass in a Horse

A 15-year-old Pony of America (POA) gelding presented for evaluation of a large mass present on the right external pinna. Based on gross appearance, the right ear mass was suspected to be neoplastic. The most likely differential diagnosis was that of a fibroblastic sarcoid. Complete auriculectomy via use of a constricting latex-tourniquet performed under multimodal analgesia was proposed as an option to achieve complete resolution of mass growth and improve patient comfort. Benefits of latex tourniquet constriction included immediate lack of bleeding associated with amputation, gradual ischemic necrosis and sloughing of tissue distant to the site of constriction, and cost-effective application. The external pinna sloughed 3 weeks following application of the constricting latex tourniquet. Complete healing was achieved within 3 months from the time of tourniquet application. The middle ear canal sealed closed as a result of auriculectomy, with no observed long-term discomfort or morbidity aside from reduction in hearing. This is the first report of total external ear amputation in the horse. Complete auriculectomy via use of a constricting latex tourniquet is a feasible method for en-bloc removal of large, complicated ear masses.

Rhomboid blepharoplasty and cryotherapy for the treatment of a squamous cell carcinoma on the lower eyelid in a horse

A rhomboid blepharoplasty can be used to achieve functional and cosmetic eyelid reconstruction at the medial canthus in the horse. Combination of a rhomboid blepharoplasty with cryotherapy is a treatment option for eyelid ocular squamous cell carcinomas.

Unilateral subcutaneous fibroma in the distal femoral region of a 5-year-old Nooitgedacht mare

A non-ossified unilateral subcutaneous fibroma was diagnosed in the distal femoral region of a 5-year-old Nooitgedacht mare. Histopathological examination of the excised mass revealed long interweaving bundles of semi-mature monotonous collagenous connective tissue with fusiform nuclei without mitotic figures. The mare made an uneventful recovery following surgical removal of the neoplasm. Subcutaneous fibromas should be considered in the differential diagnosis of skin swellings associated with the limbs of horses.

Treatment of sarcoids in equids: 230 cases (2008-2013)

OBJECTIVE To evaluate outcomes following treatment of sarcoids in equids and to identify risk factors for treatment failure in these patients. DESIGN Retrospective case series. ANIMALS 230 equids with 614 sarcoids. PROCEDURES Records were searched to identify equids treated for ≥ 1 sarcoid between 2008 and 2013. A standardized protocol was used to determine treatment choice (electrosurgery, electrosurgery with intralesional placement of cisplatin-containing beads, topical administration of imiquimod or acyclovir, cryosurgery, bacillus Calmette-Guerin vaccine injection, or intralesional injection of platinum-containing drugs). Data regarding animal, tumor, treatment, and outcome variables were collected. Complete tumor regression without recurrence for ≥ 6 months was considered a successful outcome. Success rates were calculated; binary logistic regression analysis was used to identify risk factors for treatment failure and to compare effects of the 2 topical treatments. A χ(2) test was used to compare effects of the number of Bacillus Calmette-Guerin vaccine or cisplatin-containing drug injections on outcome. RESULTS The overall success rate was 460 of 614 (74.9%). Electrosurgical excision resulted in the highest treatment success rate (277/319 [86.8%]); odds of treatment failure were significantly greater for intralesional injection of platinum-containing drugs, cryosurgery, and topical acyclovir treatment. Odds of treatment failure were also significantly greater for sarcoids on equids with multiple tumors than for solitary lesions, and significantly lower for sarcoids on equids that received concurrent immunostimulating treatment for another sarcoid than for those on patients that did not receive such treatment. CONCLUSIONS AND CLINICAL RELEVANCE Selection bias for treatments was inherent to the study design; however, results may assist clinicians in selecting treatments and in determining prognosis for equids with sarcoids treated according to the described methods.

Equine sarcoids: Bovine Papillomavirus type 1 transformed fibroblasts are sensitive to cisplatin and UVB induced apoptosis and show aberrant expression of p53

Bovine papillomavirus type 1 infects not only cattle but also equids and is a causative factor in the pathogenesis of commonly occurring equine sarcoid tumours. Whilst treatment of sarcoids is notoriously difficult, cisplatin has been shown to be one of the most effective treatment strategies for sarcoids. In this study we show that in equine fibroblasts, BPV-1 sensitises cells to cisplatin-induced and UVB-induced apoptosis, a known cofactor for papillomavirus associated disease, however BPV-1 transformed fibroblasts show increased clonogenic survival, which may potentially limit the therapeutic effects of repeated cisplatin treatment. Furthermore we show that BPV-1 increases p53 expression in sarcoid cell lines and p53 expression can be either nuclear or cytoplasmic. The mechanism and clinical significance of increase/abnormal p53 expression remains to be established.

Equine periocular neoplasia: current concepts in aetiopathogenesis and emerging treatment modalities

Neoplastic adnexal disease represents one of the most frequently encountered and therapeutically challenging ophthalmic problems of horses. This paper reviews current concepts in equine periocular neoplasia. Specifically, a literature-based review of the aetiopathogenesis of the most common tumours to affect the equine eyelid (squamous cell carcinoma, sarcoid, melanoma and lymphosarcoma) is provided. Current and emerging treatment modalities, including photodynamic therapy, are reviewed.

Management of eyelid neoplasms in the dog and cat

Eyelid neoplasms are common in the older dog and typically benign. Eyelid neoplasms in the cat are less common and more often malignant. Resection of eyelid masses may be curative; however, restoration of the eyelid structure after mass excision is essential for maintaining long-term ocular surface health. Surgical techniques and instrumentation for eyelid surgery are reviewed. Indications, benefits. and limitations of sharp excision, cryotherapy, and laser excision and ablation are discussed. Neoplasia of the third eyelid is also discussed.

Article

OBJECTIVE

To document the efficacy of intratumoural injections of 5-fluorouracil for the treatment of equine sarcoids.

DESIGN

A prospective study that included 13 horses and one donkey.

PROCEDURE

Sarcoids were confirmed by histological examination and treated with intratumoural 5-fluorouracil every 2 weeks. If the sarcoids did not resolve after seven treatments, treatment was considered a failure. All cases were re-examined 6 months after treatment commenced and owners were telephoned 3 years after commencement of treatment to report on tumour recurrence. Outcome comparisons were performed to determine the effect of previous treatment, tumour size and tumour location on sarcoid resolution. The efficacy of intratumoural 5-fluorouracil was compared with other previously documented treatments of equine sarcoids.

RESULTS

Sarcoids smaller than 13.5 cm3 were significantly (P = 0.032) more likely to resolve with treatment than larger sarcoids. Sarcoids that were not responsive to previous therapies were significantly (P = 0.007) more likely to recur after 3 years than sarcoids that had not been treated prior to this study. In this study, there were similar rates of resolution in cases with mutiple tumours (66.6%) when compared to cases with single tumours (60%). The numbers in this study were too small to properly evaluate the effect of tumour location on the success of treatment. Intratumoural 5-fluorouracil appeared to have resolved sarcoids in 9 of 13 cases (61.5%) as determined by follow up conversation with the owners 3 years after the initial treatment.

CONCLUSION

The use of intratumoural 5-fluorouracil compares favourably with other treatment modalities for sarcoids, with a long term successful resolution rate of 61.5%. Owners should be warned that resistant sarcoids and sarcoids larger than 13.5 cm3 have a poorer prognosis for resolution and more aggressive therapeutic options should be considered.

A case of multiple epitrichial sweat gland ductal carcinomas in a horse

This case report describes a rare epitrichial sweat gland ductal carcinoma in a 14-year-old horse and is the first report of multiple carcinomas of this type in horses. Although several tumours developed, mostly on the distal extremities, over a 2-year period, the horse remained otherwise healthy. Topical treatment with imiquimod was successful for many of them.

Use of cisplatin-containing biodegradable beads for treatment of cutaneous neoplasia in equidae: 59 cases (2000–2004)

OBJECTIVE

To determine outcome for equids with cutaneous neoplasms treated with cisplatin-containing biodegradable beads, alone or in conjunction with debulking.

DESIGN

Retrospective case series.

ANIMALS

56 horses, 1 zebra, 1 donkey, and 1 mule.

PROCEDURES

Medical records were reviewed. Follow-up information was obtained through telephone conversations with owners and trainers of the animals.

RESULTS

22 tumors were sarcoids, 6 were fibrosarcomas, 1 was a fibroma, 2 were peripheral nerve sheath tumors, 11 were squamous cell carcinomas, 14 were melanomas (13 gray horses and 1 bay horse), 1 was a lymphosarcoma, 1 was an adenocarcinoma, and 1 was a basal cell tumor. Forty-five (76%) animals underwent conventional or laser debulking of the tumor prior to bead implantation. Forty of 48 (83%) animals for which long-term follow-up information was available were relapse free 2 years after treatment. This included 20 of 22 animals with spindle cell tumors (including 11/13 horses with sarcoids), 6 of 10 animals with squamous cell carcinomas, 13 of 14 animals with melanomas, and 2 of 3 animals with other tumor types. Adverse effects were minimal.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that implantation of cisplatin-containing biodegradable beads, with or without tumor debulking, may be an effective treatment for equidae with various cutaneous neoplasms.