ReviewClinicopathological Presentation and Management of Penile Schwannoma
Introduction
Schwannomas (also called neurilemomas) are encapsulated tumors made entirely of benign neoplastic Schwann cells that can occur throughout the peripheral nervous system and lead to various clinical outcomes depending on the location. The tumors are sporadically associated with genetic syndromes such as schwannomatosis or neurofibromatosis or may be the result of therapeutic irradiation.1 Schwannomas have a low annual incidence of 0.6 per 100,000 people, and the vast majority were found on the flexor surfaces of limbs.2 Schwannomatosis is the third major form of neurofibromatosis, clinically and genetically distinct from neurofibromatosis 1 (NF1) and NF2. It is characterized by multiple noncutaneous schwannomas in the absence of bilateral vestibular schwannomas and is diagnosed with criteria.3 Management of schwannomas includes pharmacological treatment, surgical resection, and radiosurgery.
Penile schwannomas are extremely rare. We reviewed 36 English-language literature and found 39 cases of them. We are adding a new case of patient with penile root schwannoma, and this case may be the first penile schwannoma with schwannomatosis.
A 56-year-old male patient had been found to have a perineal nodule since the age of 35 years. Recently, he had experienced mild dysuria and tingling over the perineum during urination. He did not have dyspareunia, painful ejaculation, erectile dysfunction, or abnormal penile curvature during erection. The finding of physical examination showed a tender mass of about 5 cm in diameter located at the ventral penile root. Blood and urine chemistry findings were unremarkable.
The finding of magnetic resonance urography (MRU) showed a 5.3 × 2.9 × 2.5 cm wide extent heterogeneous mass at the base of the penis and a high signal intensity of diffusion-weighted image, involving a part of the right penile bulb and the right corpus cavernosum with extension to the perineal area (Figure 1). This mass also displaced the corpus spongiosum to the left. He also had another 3 small enhancing lesions on the dorsum of the penis, and a small right epididymal cyst was also noted on the magnetic resonance urography image. Percutaneous needle biopsy of the penile root mass showed a tumor consisting of bundles of spindle cells with wavy nuclei, scattered degenerated atypia, Verocay bodies, focal loose edematous areas, focal hemosiderin deposition, and focal hyalinized vessels. Tumor cells were diffusely and strongly positive for S-100 protein and negative for CD117 or smooth muscle actin. He was subsequently diagnosed with penile root schwannoma.
Penile-preserving excision was performed on the penile root tumor. A well-encapsulated tumor arising from the corpus cavernosum was carefully dissected free from the penile shaft (Figure 2). The eventual pathology confirmed the diagnosis of penile schwannoma (Figure 3). Other immunohistochemistry (IHC) stains were found to be positive for calretinin and SOX10 and negative for glial fibrillary acid protein (GFAP), cytokeratin AE1/AE3, and D2-40 (podoplanin) (Figure 4).
The lesions on the dorsum of the penis were barely palpable along the penis shaft and could not be found by an intraoperative ultrasound study. After discussing with the patient, we decided not to approach the asymptomatic tumors.
3 weeks later, the patient went to a dermatologist for a 1.2 × 1.0 cm brown plaque on the nape, and the specimen of excisional biopsy showed neurofibroma. He also went to an otolaryngologist for sensorineural hearing loss, headache, and tinnitus and had a follow-up for about half a year. There was no vestibular schwannoma, café-au-lait macules, axillary or inguinal freckles, optic glioma, Lisch nodules, bony lesion, meningioma, or first-degree relatives with NF1 or NF2.
Section snippets
Methods
The images, pathology, and medical records of this case were reviewed with the approval of the Institutional Review Board of the Chang Gung Medical Foundation (protocol number: 201900599B0, date of approval: 2019/04/26) with the need of receiving an informed consent signed by the patient.
We collected the English literature through the PubMed database of the National Library of Medicine up to October 2019. The titles and abstracts were screened for possible inclusion. This study excluded
Results
We collected 40 cases of penile schwannomas, including our patient. The United States had the largest number of cases (8 cases), followed by Taiwan (7 cases). In this study, we categorized lesion locations into the penile body or shaft, glans or penile root, dorsum or ventrum. Cases without full-text access or with limited descriptions or images were not categorized or analyzed in certain items, and the analyzed amount differed depending on criteria of each item. We could only analyze a maximum
Penile Schwannoma With Schwannomatosis
Although there is lack of pathological evidence of dorsal-penile lesions, their magnetic resonance imaging (MRI) presentation was similar to that of the penile base. Neurofibromas and schwannomas could both show a low signal intensity on T1-weighted images and high signal intensity on T2-weighted images.4,5 The patient may have either sporadic schwannoma and neurofibroma or schwannomatosis. In other words, if the dorsal-penile lesions are schwannomas, he is the first case of penile schwannoma
Conclusion
Penile schwannoma is extremely rare and mostly located at the penile shaft and the dorsum of the penis. Dyspareunia is the most complained symptom for sexual dysfunction. We reported the first case of penile root schwannoma in Taiwan. This study is the first study documenting the expressions of calretinin, SOX10, GFAP, D2-40 (podoplanin), and cytokeratin AE1/AE3 in penile schwannoma and claims MRI and pathologic presentations of penile schwannomas are synonymous with schwannomas from head to
Statement of authorship
Category 1 Conception and Design Liang-Chen Huang; Cheng-Keng Chuang
Acquisition of Data
Liang-Chen Huang; Hong-Zhen Wang; Yuan-Cheng Chu; Kwai-Fong Ng; Cheng-Keng Chuang
Analysis and Interpretation of Data
Liang-Chen Huang; Kwai-Fong Ng; Cheng-Keng Chuang
- (a)
Drafting the Article
Liang-Chen Huang; Cheng-Keng Chuang
- (b)
Revising It for Intellectual Content
Liang-Chen Huang; Hong-Zhen Wang; Yuan-Cheng Chu; Kwai-Fong Ng; Cheng-Keng Chuang
- (a)
Final Approval of the Completed Article
Liang-Chen Huang; Hong-Zhen Wang; Yuan-Cheng
Acknowledgments
The authors wish to thank Professor Winston W. Shen and MD. Ya-Hui Wang at Taipei Municipal Wan Fang Hospital and May Lu for assistance in editing this manuscript and acknowledge the support of the Maintenance Project of the Center for Big Data Analytics and Statistics (Grant CLRPG3D0044) at the Chang Gung Memorial Hospital.
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Conflicts of Interest: The authors declare no conflicts of interest.