Introduction
Sarcoids are locally aggressive fibroblastic tumours that are the most common neoplasm in equids, reportedly accounting for up to 67% of all neoplasms (Ragland et al. 1970; Cotchin 1977; Marti et al. 1993; Sullins et al.1986). The tumours are non-metastatic but can be very aggressive locally. Although metastatic dissemination does not occur, the tendency for exacerbation means that treatment is usually recommended, especially whilst the lesions are small and manageable (Knottenbelt et al. 2015).
Currently no treatment is available which produces repeatable resolution in all cases and the prognosis is always guarded because of the high risk of recurrence and development of new lesions (Knottenbelt et al. 2015). Numerous different treatment modalities are available, but none are universally effective, and none can be applied in all cases. The choice of which treatment to use in an individual horse will be affected by factors such as the type, location, extent and duration of the sarcoids, as well as cost. Treatment options include ligation, sharp surgical excision, laser excision and ablation, cryosurgery, hyperthermia, electrocautery, immunomodulation, autogenous vaccines, anti-viral drugs, radiotherapy and topical / intralesional chemotherapy (including electrochemotherapy). For practical reasons, topical and intralesional treatments are commonly employed in equine practice to treat sarcoids. Topical drugs include chemotherapy agents such as 5-fluorouracil, and compounds containing heavy metals, such as arsenic trioxide, mercuric chloride and antimony sulphate. One compound commonly used in the UK is AW5-LUDES cream1(sometimes referred to as the “Liverpool cream”, sourced from Equine Medical solutions), which is a formulation containing fluorouracil (an anti-metabolite chemotherapy agent) and heavy metals. The cream is strongly caustic, and there is a significant risk of spread / run-off where the material causes damage to adjacent normal tissues. This case presents a previously undocumented complication of AW5-LUDES cream treatment.