What are the causes of penile lesions?

Causes of Penile Lesions

Penile lesions arise from infectious, inflammatory, neoplastic, and vascular etiologies, with human papillomavirus (HPV) types 6 and 11 causing most genital warts, while chronic inflammatory conditions like lichen sclerosus carry a 2-9% risk of malignant transformation to squamous cell carcinoma. 1, 2

Infectious Causes

Viral Infections

• HPV infection is the most common sexually transmitted cause, with types 6 and 11 responsible for visible genital warts presenting as papillary, exophytic, or cauliflower-like lesions on the penis, vulva, scrotum, perineum, and perianal skin 1
• HPV types 16,18,31,33, and 35 are strongly associated with penile intraepithelial neoplasia and invasive carcinoma, accounting for 45-80% of penile cancers 1, 2
• Genital warts can occur on external genitalia as well as in the urethra, anus, and mouth, with intra-anal warts seen predominantly in patients with receptive anal intercourse 1

Bacterial and Fungal Infections

• Candidal balanitis presents with erythematous areas on the glans penis with pruritus or irritation 3
• Gonococcal and chlamydial infections cause urethritis with associated penile discharge and inflammation 1
• In immunocompromised patients (particularly HIV-infected), fungi and mycobacteria are more likely causes of epididymitis and penile lesions 1, 3

Inflammatory and Dermatologic Causes

Chronic Inflammatory Conditions

• Lichen sclerosus (balanitis xerotica obliterans) presents as a phimotic, hypopigmented prepuce or glans penis with a cellophane-like texture, affecting the prepuce, coronal sulcus, and glans 1, 4
• This condition carries a 2-9% risk of developing squamous cell carcinoma and requires long-term follow-up with biopsy for persistent hyperkeratosis, erosion, or new warty lesions 1, 2, 3
• Lichen planus produces pruritic, violaceous, polygonal papules that are typically systemic and may mimic carcinoma in situ 4
• Lichen nitidus usually produces asymptomatic pinhead-sized, hypopigmented papules 4

Papulosquamous Disorders

• Psoriasis presents as red or salmon-colored plaques with overlying silvery scales, often with extragenital cutaneous lesions 4
• These benign lesions may mimic carcinoma in situ or invasive squamous cell carcinoma, requiring biopsy if neoplasm cannot be excluded 4

Other Inflammatory Causes

• Chronic balanitis from poor hygiene, phimosis, or diabetes contributes to chronic inflammation and increased cancer risk 2, 3
• Phimosis is associated with 25-60% increased risk of penile cancer and significantly hinders early detection 2

Neoplastic Causes

Premalignant Lesions

• Penile intraepithelial neoplasia (PeIN) is the precursor lesion of penile squamous cell carcinoma, with clinical terms including erythroplasia of Queyrat, carcinoma in situ, and Bowen's disease 1
• Carcinoma in situ presents as velvety red or keratotic plaques on the glans penis or prepuce 4

Malignant Lesions

• Squamous cell carcinoma comprises more than 95% of penile cancers, presenting as a painless lump, ulcer, or fungating mass 1, 4
• The most common sites are the glans (34.5%), inner preputial layer, coronal sulcus, and prepuce (13.2%) 2
• HPV-associated subtypes include basaloid (4-10% of cases) and warty carcinoma (5-10% of cases) 1
• Rarer malignancies include melanocytic and sarcomatoid lesions, mesenchymal tumors, lymphomas, and metastases 1

Vascular Causes

• Angiokeratomas are typically asymptomatic, well-circumscribed, red or blue papules, often with annular or figurate configurations 4
• These vascular lesions are benign and usually require only observation 4

Traumatic and Foreign Body Reactions

• Penile trauma can lead to chronic inflammation and subsequent lesion development 2
• Foreign body reactions from implantation or injection of nonbiological materials may produce scarring, deformity, ulceration, necrosis, and even gangrene 5

Risk Factors Predisposing to Lesion Development

• Tobacco use increases risk 3.0-4.5 times for developing penile cancer 2
• HIV infection confers an 8-fold increased risk, possibly related to higher HPV co-infection rates 2
• PUVA therapy is associated with a 286 times higher risk of penile cancer 2
• History of sexually transmitted diseases increases overall risk of penile lesions and cancer 2
• Poor hygiene contributes to chronic inflammation and infection 2, 3

Critical Diagnostic Considerations

Biopsy is mandatory for lesions that are pigmented, indurated, fixed, ulcerated, or fail to respond to adequate treatment, as well as when there is any suspicion of neoplastic change 1, 3, 4

For patients presenting with penile lesions, evaluation should include syphilis serology and HIV counseling and testing, particularly when sexually transmitted infections are suspected 1