EQUINE VETERINARY EDUCATION / AE / MARCH 2015
125
tumour. The principal prognostic factors in men with carcinoma of the penis are the extent of the primary lesion and status of the lymph nodes. Tumour-free regional nodes imply an excellent long-term disease free survival rate of 85–90% (DeKernion 1973; Vogelzang et al. 2000) whilst only 40–50% of patients with regional involvement of the inguinal lymph nodes survive long term. Less than 20% of patients with pelvic lymph node involvement survive. In man, carcinoma involving the urethra also has implications regarding metastasis, for example distal urethral lesions are associated with similar prognoses as for distal penile carcinomas, whilst lesions involving the more proximal bulbo-membranous portion of the urethra carry a poor prognosis. Where regional lymph node involvement is identified in human patients with penile and/or urethral carcinoma, radical lymphadenectomy is performed. Elective radiation therapy is offered to patients with primary tumours graded as more advanced than stage 1 as these patients are considered at risk of metastasis even in the face of currently clinically normal regional lymph nodes on histopathology. As our knowledge progresses, prediction of likelihood of
metastasis is an important part of providing guidance to equine owners regarding long-term prognosis during the planning and execution of any treatment for neoplasia. A recent retrospective study examined tumour grade, presence of papilloma virus DNA in stored histopathology samples and expression of viral genes or proteins in these stored tissues in cases of equine SCC of the penis or prepuce, with an aim of identifying predictors for likelihood of metastasis (van den Top et al. 2014). Tumour grading has previously been shown to provide predictive information with regard to nodal metastasis (van den Top et al. 2008) and this more recent retrospective study by the same group found that of 19 horses in which lymph nodes were examined with histopathology perioperatively, 13 lymph nodes contained metastases with 12 of these cases having had a primary tumour graded as subtype 3 using the authors classification scheme (van den Top et al. 2014). Veterinary histopathologists are increasingly adopting the human grading system of tumours based on their degree or lack of differentiation. In light of this information and information presented in this
current case report by Nelson et al. (2015), equine surgeons may plan to consider beyond performing the gross penile and/or preputial resection procedure itself in future cases of SCC of the penis and/or prepuce. Clinicians could consider ascertaining the grade of the tumour, potentially prior to the primary surgery, via biopsy, in order to consider any need for more extensive surgery. The level and extent of involvement of the urethra as well as penile tissue should be ascertained by histopathology performed on the resected tissue post surgery. Rectal examination in order to palate for enlarged deeper lymph nodes prior to surgery on these cases is routine practice in many equine hospitals and thoracic radiographs are also often taken but consideration could be given to biopsy, or even lymphadenectomy, of the regional superficial inguinal
lymph node(s) during any surgical procedure performed on the penis or prepuce under general anaesthesia, irrespective of a grossly normal palpable appearance of these lymph nodes and to perform histopathology on this nodal tissue in order to better inform owners of the risks of potential future metastasis. The clinically normal sized equine superficial inguinal lymph node is not always readily palpable, particularly in overweight horses or in animals with preputial oedema. The superficial inguinal lymph node is generally located within the medial aspect of the proximal thigh region, close to the femoral vessels, within a triangle bounded by the inguinal ligament (base of the inguinal canal), the sartorius and gracilis muscles. Ultrasonography may be helpful in identifying the location of these lymph nodes during surgery. The pelvic lymph nodes are not surgically accessible. An excellent therapeutic algorithm to aid with decision making during evaluation of cases of SCC in the horse is detailed in the literature (van den Top et al. 2011). Development of an equine database recording primary
tumour types identified and further graded with histopathology and presence or not of metastases at post mortem examination may provide clinicians with further guidance as to the prevalence of metastases and their most typical locations for given tumour types for future reference.
Author’s declaration of interests No conflicts of interest have been declared.
References
Brinsko, S.P. (1998) Neoplasia of the male reproductive tract. Vet. Clin. N. Am.: Equine Pract. 14, 517-533.
DeKernion, J.B. (1973) Carcinoma of the penis. Cancer 32, 1256-1262.
Jann, H.W., Breshears, M.A., Allison, R.W., Pechman, R.D., Day, J., Hart, J.C.A. and Moorman, V.J. (2009) Occult metastatic intestinal adenocarcinoma resulting in pathological fracture of the proximal humerus. Equine Vet. J. 41, 915-917.
Lavach, J. and Severin, G. (1977) Neoplasia of the equine eye, adnexa, and orbit: a review of 68 cases. J. Am. Vet. Med. Ass. 170, 202-203.
Nelson, B.B., Edmondson, E.F., Sonis, J.M., Frank, C.B., Valdés-Martinez, A. and Leise, B.S. (2015) Multiple skeletal metastases from a penile squamous cell carcinoma in a horse. Equine Vet. Educ. 27, 119-123.
van den Top, J.G.B., De Heer, N., Klein, W.R. and Ensink, J.M. (2008) Penile and preputial tumours in the horse: a retrospective study of 114 affected horses. Equine Vet. J. 40, 528-532.
van den Top, J.G.B., Ensink, J.M., Barneveld, A. and Van Weeren, P.R. (2011) Penile and preputial squamous cell carcinoma in the horse and proposal of a classification system. Equine Vet. Educ. 23, 636-648.
van den Top, J.G.B., Harkema, L., Lange, C., Ensink, J.M., Van De Lest, C.H.A., Barneveld, A., Van Weeren, P.R., Grone, A. and Martens, A. (2014) Expression of p53, ki67, EcPV2 and EcPV3 DNA and viral genes in relation to metastasis and outcome in equine penile and preputial squamous cell carcinoma. Equine Vet. J. Epub ahead of print; doi: 10.1111/evj.12245.
Vogelzang, N.J., Scardino, P.T., Shipley, W.U. and Coffey, D.S. (2000) Comprehensive Textbook of Genitourinary Oncology, 2nd edn., Lippincott, Williams and Wilkins, Philadelphia.
© 2015 EVJ Ltd
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88
