• Basal cell tumours (BCT) are rare in horses. In one American study, it was suggested that around 1.2% of all lesions biopsied from the skin of horses were BCT (Schaffer et al. 2013).
  • They can occur in any equid at any age but are found predominantly in animals over 6 years of age.
  • They are invariably benign neoplasms but can be locally invasive.
  • Malignant forms are extremely rare
  • They normally appear as single, solitary, sometimes ill defined, firm, nodular skin mass/es. Changes can be present in the overlying epidermis such as alopecia (hair loss), hyperpigmentation or ulceration.
  • Generally, they measure <5 cm in diameter but larger ones are occasionally found.
  • They can be easily confused with sarcoids, squamous cell carcinoma, melanoma, trichoepithelioma, sebaceous or apocrine neoplasms or non-neoplastic follicular cysts, foreign body granuloma and pyogranuloma.
  • Diagnosis is made by biopsy and histological confirmation.
  • Full excision is nearly always curative.

Figure 1 Image of a slow growing Basal Cell Carcinoma (BCC) on the tail of a 14-year-old -gelding. The similarity to sarcoid is striking



Where does it occur?


They are most commonly found on the

  • Trunk / tail
  • Distal Limb this is the most common predilection site
  • Face
  • Neck

There have been reports of lesions also occurring on the eyelids, nictitating membranes, pectoral area, commissure of the mouth, vulva, buttocks, prepuce and tail.

Figure 2: A complex basal cell carcinoma on the tail – notice the aggressive appearance and the similarity to sarcoid, carcinoma dn some other tumour types. Although the condition looks bad it is seldom malignant. This does not however mean that treatment is easy!

Figure 3:   A slow growing basal cell carcinoma on the inside of the hock. The tumour was a surgical challenge but resolved as expected.



  • Full surgical excision is generally curative (Slovis et al. 2001)

Figure 4: An ulcerated BCC on the buttock region that has developed over some months originally from a small cutaneous nodule. The tumour is often progressive and early recognition




  1. Cryosurgery
  2. Laser excision
  3. Intralesional chemotherapy





The prognosis is excellent if full excision is achieved. Recurrenceand / or mMetastasis are very rare following full removal.



Knottenbelt DC, Patterson Kane J. and Snalune K. Basal cell tumour. Clinical Equine Oncology, Elsevier, 2015 pp.252 &563

Schaffer PA., Wobeser B, Martin LE et al. Cutaneous neoplastic lesions of equids in the Central United States and Canada: 3351 biopsy specimens from 3272 equids (2000-2010) J Am Vet Med Assoc 2013. 242 pp 99-104.

Back to Top