What are the causes and treatments of a lump on the penile shaft?

Evaluation and Management of a Penile Shaft Lump

A lump on the penile shaft requires immediate physical examination with biopsy for any suspicious lesion, as malignancy must be excluded first, though benign causes are more common in this location.

Initial Diagnostic Approach

Physical Examination Priorities

• Document lesion characteristics systematically: diameter, exact location on shaft, number of lesions, morphology (papillary, nodular, ulcerous, or flat), and relationship to deeper structures (submucosal, corpora spongiosa/cavernosa, urethra) 1
• Assess for concerning features: pigmentation, induration, fixation to underlying structures, ulceration, or irregular borders 1
• Examine inguinal regions bilaterally for lymphadenopathy, as this may indicate metastatic disease if malignancy is present 1

When to Biopsy Immediately

Obtain punch, excisional, or incisional biopsy for any lesion that is pigmented, indurated, fixed, ulcerated, or when diagnosis is uncertain 1. Histological confirmation is mandatory before initiating treatment with topical agents, radiotherapy, or laser therapy 1.

Differential Diagnosis by Clinical Presentation

Malignant Lesions (Must Rule Out First)

• Squamous cell carcinoma: While only 5.3% of penile cancers occur on the shaft (compared to 34.5% on glans), this location still requires exclusion 1
• Bowenoid papulosis: Typically presents as raised papules on penile shaft skin in younger males with HPV exposure history 1
• Bowen's disease: Appears as red scaly patches on the penile shaft 1

Benign Lesions (More Common on Shaft)

• Thrombosis of corpus cavernosum: Presents as palpable lump with perineal pain and erectile dysfunction; MRI shows non-enhancing thrombus 2
• Schwannoma: Rare but characteristic presentation of single painless nodule on dorsal shaft, slow-growing over average 62 months, may cause sexual dysfunction 3, 4
• Lymphedema: Can present as penile shaft swelling following recurrent furunculosis or infection 5
• Granuloma annulare: Rare localized presentation requiring biopsy for diagnosis 6

Imaging Studies

When to Order MRI or Ultrasound

• MRI is indicated when uncertainty exists about invasion of cavernosal bodies (distinguishing T1 from T3 disease) or when organ-sparing treatment is considered 1
• Ultrasound can substitute if MRI unavailable 1
• MRI is diagnostic for corpus cavernosum thrombosis, showing non-enhancement that differentiates from other lesions 2

Risk Factor Assessment

High-Risk Features Requiring Aggressive Workup

• Chronic inflammation history: balanitis, lichen sclerosus (2-9% malignancy risk), penile trauma 1
• HPV exposure: 45-80% of penile cancers are HPV-related, particularly types 16 and 18 1
• Tobacco use: 3.0-4.5 times increased cancer risk 1
• HIV infection: 8-fold increased cancer risk 1
• Poor hygiene and phimosis: 25-60% increased cancer risk with phimosis 1

Treatment Algorithm Based on Diagnosis

If Malignancy Confirmed

• Penile-sparing approaches preferred when feasible: topical therapy (imiquimod or fluorouracil), wide local excision including circumcision, laser therapy, or complete glansectomy 1
• Partial penectomy is standard for high-grade tumors if functional penile stump can be preserved with negative margins 1
• Lymph node assessment required for T1G2 or higher lesions, even if clinically node-negative 1

If Benign Lesion Confirmed

• Schwannoma: Surgical excision is curative; all reported cases achieved full remission 4
• Corpus cavernosum thrombosis: Oral anticoagulation plus PDE-5 inhibitor to prevent progression and maintain erectile function 2
• Lymphedema: Excision of lymphedematous tissue with flap reconstruction 5

Critical Pitfalls to Avoid

• Never assume a shaft lump is benign without tissue diagnosis, especially in patients over 50 years or with risk factors 1, 7
• Do not delay biopsy for lesions with any concerning features, as early detection significantly improves survival (>85% for node-negative disease vs 50% overall) 7
• Phimosis can hide malignancy: If present, circumcision may be necessary for adequate examination 1
• Palpable inguinal nodes at diagnosis are inflammatory in 50% of cases, but nodes appearing during follow-up are malignant in nearly 100% 1