Premalignant Lesions of the Penis

Classification Overview

I. Penile Intraepithelial Neoplasia (PeIN / PIN)

1. Erythroplasia of Queyrat (EQ)

• Definition: CIS involving the glans penis or prepuce of uncircumcised men
• Named after: Queyrat, who first described it in 1911
• Clinical: Red, velvety, well-marginated lesion; may ulcerate; may be associated with discharge and pain
• Histology:
  • Normal mucosa replaced by atypical hyperplastic cells
  • Disorientation, vacuolation, multiple hyperchromatic nuclei, mitotic figures at all levels
  • Epithelial rete extended into submucosa - elongated, broadened, bulbous
  • Submucosa: capillary proliferation and ectasia with inflammatory infiltrate rich in plasma cells (distinguishes from chronic balanitis)
• Malignant transformation: 10-33% progress to invasive carcinoma
• Note: No associated visceral malignancy

2. Bowen's Disease (BD)

• Definition: CIS involving the penile shaft or remainder of genitalia/perineal region
• Named after: Bowen (1912), who described it as an intraepithelial neoplasm associated with subsequent internal malignancy - however, subsequent case-control studies showed no association with internal tumors, so penile CIS does not warrant a search for internal malignancy
• Clinical: Sharply defined plaques of scaly erythema on the penile shaft; crusted or ulcerated variants; may mimic bowenoid papulosis, nummular eczema, psoriasis, or superficial BCC
• Histology: Dysplastic squamous cells with large hyperchromatic irregular nuclei, lacking orderly maturation; numerous mitoses (some atypical) (Fig. 21.13 from Robbins)
• Malignant transformation: Invasive carcinoma in ~5-10% of untreated patients; metastasis extremely rare but reported

3. Bowenoid Papulosis (BP)

• Definition: Histologically identical to CIS but a clinically benign course
• First described by: Kopf and Bart (1977)
• Clinical: Multiple reddish-brown papular lesions on the penis; affects younger, sexually active adults (peak incidence in the 3rd decade)
• Etiology: HPV-16 (now classified as HSIL - high-grade squamous intraepithelial lesion)
• Key distinction from Bowen's Disease:
  • Multiple (not solitary) lesions
  • Younger patients
  • Virtually never progresses to invasive carcinoma
  • Usually regresses spontaneously
• Histology: Indistinguishable from Bowen's disease (hence the importance of clinical context)

II. Non-HPV / Inflammatory Premalignant Lesions

4. Leukoplakia

• Appearance: White plaque typically involving the meatus; most common in diabetic patients
• Histology: Acanthosis, hyperkeratosis, parakeratosis
• Significance: May precede or occur simultaneously with penile carcinoma

5. Balanitis Xerotica Obliterans (BXO) / Male Lichen Sclerosus (LS)

• Definition: A genital variation of lichen sclerosus et atrophicus; non-HPV related
• Clinical:
  • Whitish patch on the prepuce or glans, often involving the meatus and fossa navicularis
  • Lesions may be multiple with a mosaic appearance
  • Meatus appears white, indurated, edematous
  • Glanular erosions, fissures, meatal stenosis
  • Symptoms: pain, dyspareunia, pruritus, painful erections, urinary obstruction
  • Most common in uncircumcised men, middle-aged (rarely in boys)
  • Almost never occurs in males circumcised at birth
• Histology:
  • Atrophic epidermis with loss of rete pegs
  • Homogenization of collagen in upper third of dermis
  • Zone of lymphocytic and histiocytic infiltration
• Malignant risk: Found in 28-50% of patients with penile cancer; penile cancer develops in 2.3-5.8% of men with LS
• Etiology: Unknown; autoimmunity, genetic factors, chronic inflammation, possibly Borrelia burgdorferi (identified in 63% of LS tissues in one study - causation unproven)
• Treatment: Clobetasol propionate cream for 2-3 months; meatal stenosis may require repeated dilations, corticosteroid injection, or reconstructive surgery

6. Cutaneous Horn

• Appearance: Animal horn-like protuberance from overgrowth and cornification of epithelium
• Histology: Extreme hyperkeratosis, dyskeratosis, acanthosis
• Key point: The horn itself is not the concern - the underlying lesion matters:
  • Benign: seborrheic keratosis, viral warts
  • Premalignant: solar keratosis, Bowen disease
  • Malignant: SCC found at the base in up to 33% of penile horns
• Predisposing factors: Chronic inflammation, trauma, poor hygiene, viral infection
• Treatment: Surgical excision with a margin of normal tissue around the base; full histologic evaluation essential; close follow-up (may recur or transform)

7. Pseudoepitheliomatous Keratotic and Micaceous Balanitis (PKMB)

• Appearance: Hyperkeratotic, scaly, micaceous (mica-like, silver-white, layered) growth on the surface of the glans penis
• Histology: Marked hyperkeratosis, parakeratosis, pseudoepitheliomatous hyperplasia
• Differential diagnosis: Verrucous carcinoma, SCC, giant condyloma, penile horn, keratoacanthoma
• Staging (Krunic et al.):
  1. Initial plaque
  2. Late tumor stage
  3. Verrucous carcinoma
  4. Invasive squamous cell carcinoma
• Treatment: Topical 5-fluorouracil, surgical excision, laser ablation, or cryotherapy (based on stage); tends to recur as frank carcinoma with less invasive treatment - requires close follow-up and prompt excision

Histology Image: Condyloma Acuminatum (HPV-associated benign precursor)

Treatment of PeIN (General Principles)

Summary Table

Bowen's Disease vs. Bowenoid Papulosis

Comparison Table

The Key Paradox

• Caused by HPV-16
• Histologically indistinguishable (CIS-level changes, koilocytosis, disordered maturation, atypical mitoses)

Memory Hook

"Bowen = Big risk, Bowenoid = Benign course"

• Bowen: Solitary, Older, Shaft, 5-10% → SCC
• Bowenoid Papulosis: Multiple papules, Young adults, Regresses

Why Biopsy Alone Cannot Distinguish Them

• Multiple lesions in a young sexually active person → Bowenoid Papulosis
• Solitary plaque in an older man → Bowen's Disease

Benign Tumours of the Penis

I. Epithelial / HPV-Related Benign Tumours

1. Condyloma Acuminatum (Genital Warts / Venereal Warts)

• Cause: HPV types 6 and 11 (low-risk, non-oncogenic)
• Sites in males: Glans, penile shaft, prepuce, meatus (most common sites). About 5% have urethral involvement, which may extend to the prostatic urethra. Rarely, bladder involvement occurs.
• Clinical appearance: Soft, papillomatous, friable growths. May be:
  • Solitary on a pedicle, OR
  • Multiple in a moruloid cluster on a broad base
  • "Cauliflower-like" appearance
• Histology:
  • Outer layer of keratinized tissue covering papillary fronds
  • Fronds supported by connective tissue stroma
  • Well-ordered rows of squamous epithelial cells
  • Dermal lymphocytic infiltrate
  • Koilocytes - pathognomonic for HPV: cells with an empty perinuclear cavity (halo) surrounding an atypical nucleus; prominent keratohyalin granules
• Diagnosis: Subclinical lesions detected by applying 5% acetic acid to penis - lesions turn white (acetowhite); flat lesions invisible on inspection become apparent. Biopsy confirms diagnosis.
• Malignant potential: Condylomata acuminata are not precancerous per se. However, malignant transformation to SCC has been reported, and they are associated with penile SCC.

Important: No treatment has been proven to reduce transmission to sexual partners or prevent progression to dysplasia/cancer. Recurrence is common after any treatment.

2. Buschke-Löwenstein Tumour (Giant Condyloma Acuminatum)

• First described: Buschke and Löwenstein (1925)
• Cause: HPV types 6 and 11 (same as condyloma)
• Key distinction from ordinary condyloma:
  • Ordinary condylomata, regardless of size, remain superficial and never invade adjacent tissue
  • Buschke-Löwenstein tumour displaces, invades, and destroys adjacent structures by compression
  • Does not metastasize (unlike true carcinoma)
• Location: Glans, prepuce, perineum; also perianal region
• Histology:
  • Luxuriant mass of broad, rounded rete pegs extending deep into tissue
  • Composed of well-differentiated squamous cells with no cellular anaplasia
  • Dense band of acute and chronic inflammatory cells surrounding epithelial pegs
• Malignant risk: In the perianal region, 30-56% are associated with an existing carcinoma; mortality ~20%
• Diagnosis: Excisional biopsy or multiple deep biopsies required to distinguish from true penile carcinoma
• Treatment:
  • Complete surgical excision (optimal) - may require skin graft reconstruction in extensive cases
  • Recurrence is common; close follow-up essential
  • Podophyllin, 5-FU, and radiation therapy are ineffective (thickened stratum corneum impervious to topical agents)
  • Systemic interferon + Nd:YAG laser: reported success in lower-volume disease

II. Non-Epithelial Benign Penile Tumours

III. Other Benign / Inflammatory Lesions Sometimes Grouped with Benign Tumours

Peyronie's Disease

• Hard penile plaques in the connective tissue between corpora cavernosa and tunica albuginea
• Results from collagen deposition secondary to microvascular trauma and organizing sclerosing chronic inflammation
• Not neoplastic - reactive
• Clinical: penile curvature toward the lesion + pain during intercourse
• Treatment: surgery or collagenase (Xiaflex) injection to lyse fibrous plaques

HPV Vaccination (Prevention)

• Gardasil (quadrivalent): Protects against HPV types 6, 11, 16, 18
• FDA approved for females (2006) and males (2010), ages 9-26 years
• Provides excellent protection against low-risk HPV (types 6 & 11) - prevents condylomata
• Also protects against high-risk HPV (16 & 18) - prevents PeIN and SCC

Summary