Laser surgery as a treatment for histologically confirmed sarcoids in the horse

Equine sarcoids: A clinicopathologic study of 49 cases, with mitotic count and clinical type predictive of recurrence

Sarcoids are common mesenchymal neoplasms of horses. Although there are few studies in which sarcoids have been followed over a long period of time, sarcoids are considered locally invasive and have been reported to frequently recur following surgical excision. Currently, no histological features have been identified to predict which sarcoids will recur after excision. The present study comprised 49 sarcoids for which histology sections were available and in which the recurrence status of the case was known. Each sarcoid was excised from a different horse. Overall, 12 of the 49 (24%) sarcoids recurred after surgical excision. Mitotic count (MC), cellularity, necrosis, nuclear pleomorphism, and inflammation of the sarcoids were evaluated histologically. Of these, MC correlated with recurrence. Four of 5 (80%) sarcoids with an MC ≥ 20 in 2.37 mm2 recurred, which was a significantly higher recurrence rate than that of sarcoids with an MC < 20, 8 of 44 cases recurred (18%), P = .0051. Clinical type was also found to correlate with recurrence. Three of 4 (75%) fibroblastic types recurred, which was a significantly higher recurrence rate than that of sarcoids with other clinical types, 9 of 45 cases (18%), P < .001. In addition, univariate Cox regression analysis confirmed fibroblastic type and MC ≥ 20 as significant predictors for recurrence (P = .016 and P = .005, respectively). To the authors' knowledge, this is the first large study examining recurrence rates in sarcoids, and the first time that histological features have been correlated with recurrence.

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.

Histological evidence of superficial inflammation is associated with lower recurrence of equine sarcoids following surgical removal: A follow-up study of 106 tumours in 64 horses

Although the equine sarcoid is the most common skin neoplasm in domesticated horses, histopathological characteristics have not previously been evaluated for association with recurrence. The aim of this retrospective cohort study was to investigate clinical and histopathological features of excised equine sarcoids and to evaluate their association with recurrence at the original surgical site and at new sites. Clinical records and excisional biopsies from 106 equine sarcoids from 64 horses referred to Leahurst Equine Hospital, University of Liverpool, between March 2010 and February 2015 were retrieved. Biopsies were re-evaluated histologically. Clinical data were obtained from hospital records, and owner-reported follow-up data were obtained by telephone questionnaire. Associations between clinical and histopathological features of sarcoids and their recurrence at the surgical site were determined using uni- and multivariable mixed effects logistic regression. Recurrence of sarcoids at the surgical site occurred in 30 horses (46.9%). Sarcoids developed at a distant site in 21 horses (32.8%). In the final mixed effects logistic regression model, only superficial inflammation was associated with reduced odds of recurrence at the surgical site (adjusted odds ratio, 0.32; 95% confidence intervals, 0.10-0.96; P = 0.04). This suggests that the inflammatory process may play a role in protecting horses against the recurrence of sarcoids.

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.

ALVAC-fIL2, a feline interleukin-2 immunomodulator, as a treatment for sarcoids in horses: A pilot study

Background

Sarcoid tumors are common in horses and may negatively impact the performance and value of the horse. No known treatment is reliably successful.

Hypotheses/Objectives

To determine tolerability, overall response rate, time to response, and progression‐free survival of horses with biopsy‐confirmed or suspected sarcoids treated with ALVAC‐fIL2.

Animals

Client‐owned horses with measurable, presumed‐ or biopsy‐confirmed sarcoid tumors.

Methods

Prospective pilot study. One milliliter of ALVAC‐fIL2 was injected into 4 to 5 areas of the sarcoid(s) in each horse (week 0); this treatment was repeated in weeks 1, 3, and 7. Sarcoids were measured at each visit, and response to treatment was determined according to the Response Evaluation Criteria in Solid Tumors for dogs (v1.0). After the final treatment, horses were reassessed and sarcoids remeasured every 3 months until tumor progression or for a minimum of 1 year if progression was not documented.

Results

Fourteen horses were included. Tumor size decreased in 86% of the horses, and the median time to first response was 89 days (range, 34‐406 days). Median time to best response was 211 days (range, 56‐406 days), but 3 of the sarcoids still were decreasing in size at the time of final evaluation. The median progression‐free interval was not reached. Adverse events were minimal and included transient focal inflammation in 2 horses.

Conclusions and Clinical Importance

Intratumoral injection of ALVAC‐fIL2 has promise as a well‐tolerated and effective, tissue‐sparing treatment for horses with sarcoid tumors.

Surgical Debulking and TransEndoscopic Noncontact Diode Laser Application for Treating a Sinonasal Myxoma in a Horse

Equine sinonasal myxomas (SNM) are very rare; only a few cases/small case series are reported in veterinary literature. The purpose of this report is to describe the diagnostic and surgical procedure adopted to approach the neoplastic mass in a case of equine SNM. A 5 year old, Murgese gelding was presented with mild serous nasal discharge, minimal facial swelling, decreased airflow from the right nostril, and dull frontal sinus percussion. Diagnostic imaging, including endoscopy, revealed a pale mass in the caudal portion of the right middle meatus, which developed inside the right conchofrontal sinus and nasal cavity and deviated the nasal septum to the left side. A large frontonasal bone flap was created with the horse in general anesthesia, aiming to remove the lesion and perform further diagnostic investigation. The mass had the shape of a small orange, the caudodorsal and rostral part having a hard wall, whereas the ventral part being friable; the inside was hollow, containing a viscous and transparent liquid. Surgical excision was broad but incomplete, and therefore after surgery, a standing transendoscopic diode laser irradiation and photoablation of small residual lesions per nasum were performed. Microscopically, the mass consisted of spindle-shaped cells, loosely arranged within an abundant, light blue myxoid matrix. On the basis of clinical and pathologic findings, the diagnosis of sinonasal myxoma was made. Although benign and slowly growing, myxomas usually tend to infiltrate the surrounding tissues; as a consequence, recurrence is very likely after surgical excision. In the case described herein, the combination of a surgical excision, transendoscopic diode laser irradiation, and photoablation provided a positive outcome, until at least 14 months after surgery.

The Equine Sarcoid: Why Are There so Many Treatment Options?

This article discusses the main treatments for sarcoid and the specific difficulties of these. It explains to some extent why the frustrations of a condition for which there is no single treatment option have led to the burgeoning of an industry of irrational treatments. The factors that need to be considered before selecting an option for treatment are wider than is the case in most other disease entities as a result of the complexity of the condition, its variable phenotypes, and the individual perceptions and experiences of both veterinarians and owners.