• Penile neoplasia includes: fibrous papilloma, squamous cell carcinoma, sarcoid, melanoma.
• Tumors may be either benign (papilloma/sarcoid/melanoma) or malignant (sarcoid, squamous cell carcinoma).
• Tumors are most commonly situated on the glans. Precarcinomatous changes can be seen on skin of penis away from glans.
• Rarely occur on the body or other locations.
• May occur in association with preputial tumors.

Presenting signs

Squamous cell carcinoma

• Shows a predilection for the penis and the internal laminae of the prepuce Penis: squamous cell carcinoma.
• Some cases of squamous cell carcinoma of the penis present with a very firm 'wooden' feel to the glans and part of the free part of the penis (usually in younger geldings 4-10 years); this form has a much higher propensity for malignancy.
• Visible when the penis is extended.
• Swelling of the prepuce that extends deep into the inguinal region.
• Precarcinomatous changes show florid, slightly ulcerated, mildly painful lesions with exudate.
• May be pedunculated or sessile.
• Can grow to tennis ball size or larger, covering the entire glans.
• Typical mass is cauliflower-like (proliferative form).
• Ulcerating/destructive forms cause extensive tissue destruction.
• Slight caseous exudation or bloody preputial discharge.
• Bleeds easily.
• Metastases, especially to the superficial and deep inguinal lymph nodes and iliac lymph nodes.
• Contact metastases as a result of mucosal irritation due to prolonged contact with the visceral and parietal layers of the prepuce → the area of the preputial ring forming the site of predilection for such lesions.

Papilloma

• Papillomatous masses, often in large numbers Papillomatosis.
• May be pedunculated, though most are sessile.
• Tumor surface is rough and may show fissuring.
• Range in size from minute to large growths that involve the penis and glans.
• Tendency to bleed easily after breeding (due to thin epithelium).
• Heavy exudation on contact with smegma possible.  

Sarcoid

• Nodular form is commonest on penis/internal sheath Sarcoid. Also on penile shaft in nodular form.
• Frequently develop on the preputial skin and mucosa.

Melanoma

• Usually well circumscribed .
• Often multiple.
• Characteristic black color.
• Sometimes ulcerated.

Age predisposition

• Carcinomas are most commonly seen in older horses, squamous cell carcinomas Penis: squamous cell carcinoma especially in older geldings. If condition is seen in younger geldings <8-10 years, high malignancy is possible. Usually 'wooden' feel to penis. Extremely rare in working stallions.
• Papillomas affect primarily young animals.

Breed/Species predisposition

• It has been suggested that aged pony geldings are more commonly affected with squamous cell carcinoma than castrated horses.

Cost considerations

• Surgical treatment can be expensive.
• Conservative treatment is moderately expensive and requires on-going management (often for life).