Glomus tumour of the male urethra: an unusual diagnostic

Abstract

A 56-year-old man was referred to a reconstructive urologist for evaluation of a tender nodule in the penoscrotal area. Penile Doppler ultrasound showed a non-compressible mass with internal vascularity within the corpora spongiosum, and MRI identified an enhancing, solid mass arising from the ventral aspect of the urethra. Surgical resection warranted partial excision and reconstruction of the urethra, which was achieved by a dorsal onlay buccal mucosal graft urethroplasty through a perineal incision with penile invagination. The histopathology report concluded to an invasive, high-grade urothelial carcinoma, for which an aggressive oncological approach was considered. However, discussion with the pathology team led to the identification of a glomus tumour for which the patient did not need additional procedures. Urethral glomus tumours are extremely rare and should be included in the differential diagnosis of urethral masses. This case exemplifies the importance of teamwork in the management of uncommon cases.

Background

Glomus bodies are neuromyoarterial receptors located in the dermis layer of the skin and involved in body temperature and peripheral blood flow regulation. Masson accurately described glomus bodies and tumours in 1924.¹ They consist of an afferent arteriole, an efferent venule and an anastomotic Suquet-Hoyer canal surrounded by a capsule of connective tissue. They are scattered in the skin, but predominantly abundant in the fingers and toes, found most specifically in the subungual location.²

Glomus tumours are benign soft tissue tumours of the skin resulting from growth of one or more components of normal glomus bodies and are generally small, painful, encapsulated nodules.² Although they are primarily found under the nails, they have been described in several other organs. Involvement of the male genitalia is extremely rare with only 11 reported cases in the penis,^3–5 3 in the scrotum^6–8 and 1 in the testicle.⁹ Three cases of periurethral glomus tumours in females have been published,^10–12 but only one case has been documented in the male urethra.¹³

We describe the case of a man diagnosed with an anterior urethral mass treated by open surgical excision and reconstruction with buccal mucosal graft (BMG) urethroplasty. After the initial histopathological review, the mass was thought to be an aggressive urothelial tumour, and a radical surgical approach was planned. However, in light of the clinical presentation, the uncommonness of urethral malignant tumours and the potentially debilitating treatment to come, the case was rediscussed with the pathologist. After further review, the final diagnosis ended up being a glomus tumour, therefore a benign lesion, and no additional treatment was required. The case illustrates the importance of correlating clinical presentation with objective findings and the critical role of dialogue between colleagues of different medical specialties.

Case presentation

A 56-year-old man with no significant medical or surgical history consulted a urologist because of a newly discovered painful mass in the penoscrotal region. He had being complaining of tenderness in this area for the last year. He had neither gross haematuria, lower urinary tract symptoms, nor erectile dysfunction. On examination, he had a 1.5 cm tender nodule in close proximity with the urethra at the level of the penoscrotal junction.

Investigations

A penile Doppler ultrasound was initially performed and revealed a 1.3×0.8×0.9 cm non-compressible mass with internal vascularity within the corpora spongiosum, but MRI was recommended to better delineate the anatomy considering the atypical location of the lesion and the unknown origin. High-resolution multiplane T1W and T2W sequences with and without fat suppression and T1 postcontrast sequences were obtained (figure 1). A 1.1 cm smooth, enhancing, solid mass arising from the right ventral aspect of the urethra and contained within the corpus spongiosum was identified approximately 8 cm distal to the membranous urethra. The mass appeared to be indenting the urethral mucosa significantly.

Figure 1.

T2W MRIs obtained in (A) axial, (B) sagittal and (C) coronal planes, and showing a urethral mass with low signal intensity. Intraurethral lignocaine gel can be visualised on the coronal plane (high signal intensity) and assists in illustrating the narrowing of the urethral lumen due to the external compression caused by the mass.

Treatment

Considering the rarity and complexity of the case, the patient was then referred to an experienced reconstructive urologist for definitive treatment. Flexible urethrocystoscopy confirmed the mass location and demonstrated that it was not protruding in the urethral lumen, but rather causing a compressing effect, as the mucosa appeared perfectly healthy. Minor urethral stricture disease was noted slightly proximal to the mass. Different surgical approaches were then discussed. A perineal approach with penile invagination was deemed the most appropriate option to insure optimal access and visualisation of the diseased urethra. Exposure and dissection of the urethra were therefore obtained in this manner. To achieve complete resection of the mass, the urethra had to be partially excised and reconstructed. The dorsal urethrotomy was extended to encompass the strictured area, a BMG was harvested from the left cheek, and a dorsal onlay BMG urethroplasty was performed (figure 2).

Figure 2.

Intraoperative pictures showing (A) the urethrotomy and the mass arising from the right ventral aspect of the anterior urethra and (B) the full penile invagination and final result after buccal mucosal graft urethroplasty.

Outcome and follow-up

The original histopathology report by an experienced genitourinary pathologist concluded to an invasive, high-grade urothelial carcinoma with invasion of the corpus spongiosum and areas of lymphovascular invasion. The tumour did not have the typical morphology of papillary urothelial carcinoma, which raised the possibility of a large nested variant or urothelial carcinoma. These results initially steered us towards an aggressive oncological approach, with consideration of a radical cystoprostatectomy, pelvic lymphadenectomy and total penectomy. However, taking into account the unexpected diagnosis and rarity of the disease, the pathologist was contacted and the clinical scenario was clarified. Slides were reviewed and a panel of immunoperoxidase stains were performed and led to the identification of a glomus tumour through the strongly positive staining of the tumour for smooth muscle actin (SMA) (figure 3). The patient recovered successfully from his urethroplasty and did not need additional surgery.

Figure 3.

(A) Low power view of the edge of the tumour extending into the vascular spaces of the corpus spongiosum (H&E, x10 magnification). (B) High power view of the tumour projecting into the vascular spaces (H&E, x200 magnification). (C) Immunohistochemistry for smooth muscle actin showing strong staining of the tumour cells (x200 magnification). (D) Immunohistochemistry for CD31 showing an attenuated lining of CD31 positive endothelial cells covering the tumour where it bulges into the vascular spaces (x200 magnification).

Discussion

Glomus tumours are rare, representing solely 1.6% of all soft tissue tumours and are most often located in the digits.¹⁴ A number of hand surgeons advocate clinical diagnosis, while others support the use of preoperative MRI.¹⁵ Various other imaging modalities have been studied but they mostly generate inconsistent results. Ultrasonography appears to be fairly accurate but is unable to detect small lesions.¹⁵ On MRI, glomus tumours usually show low signal intensity on T1W sequences, high signal intensity on T2 sequences, and enhancement on T1 images after gadolinium injection.^{13 15} However, these findings are not specific for glomus tumours. Al-Qattan et al investigated the sensitivity, specificity and predictive values of MRI in the diagnosis of glomus tumours of the hand and reported sensitivity of 90%, specificity of 50%, positive predictive value of 97% and negative predictive value of 20%.¹⁵ Based on this information, we gather that MRI can be a helpful adjunct to the diagnosis of glomus tumours but is not mandatory in the investigation of tumours found in typical locations. The use of imaging modalities has not been described in the few published cases of periurethral/urethral glomus tumours.^10–13 In our case, ultrasound and MRI aided in eliminating a number of possible diagnoses, defining the anatomy and surgical planning. It is reasonable to consider these imaging modalities in the work up of periurethral/urethral lesions of unknown aetiology.

Although glomus tumours in standard locations are usually clinically diagnosed, the definitive diagnosis for tumours in atypical sites is done through histopathology and immunochemistry.¹³ Histologically, glomus tumours are made up of glomus cells, smooth cells and vessels.¹⁶ These tumours are typically circumscribed, often surrounded by a fibrous capsule, and include narrow vessels with many layers of glomus cells.¹⁷ Our tumour was circumscribed, but unencapsulated, composed of sheets of ovoid cells with ill-defined cytoplasm, and included delicate branching vessels ramifying through it. As it has been described in previous cases, there were very little atypia and no mitoses.^{8 18} Almost all glomus tumours stain positively for vimentin and muscle actin isoforms, making immunohistochemistry valuable in their diagnosis.¹⁹ In the current case, immunohistochemistry was indeed instrumental to establish the diagnosis through the positive staining for SMA. However, in this case, it is primarily the history and clinical suspicion that were of the utmost importance, since this led to a challenge of the initial pathology review and to a drastically different diagnosis. Since periurethral/urethral glomus tumours are exceptionally rare, they could not have been part of an initial differential diagnosis in this particular case, but the clinician must be aware of the variety of non-neoplastic urethral tumours and follow clinical instinct as the final diagnosis might have a tremendous impact on further management.

As demonstrated in table 1, there is a paucity of literature about periurethral/urethral glomus tumours. Three periurethral glomus tumours have been described in female patients and have all been surgically excised without the need for urethral reconstruction.^10–12 In one of these patients, a residual tumour had to be removed at 10 months, but there was no additional recurrence 10 years later.¹⁰

Table 1.

Published cases of glomus tumour in the periurethral/urethra region

Reference	Gender	Age at diagnosis (years)	Clinical presentation	Tumour characteristics	Treatment	Immunohistochemistry
Sonobe et al 10	F	46	Painful vulvar nodule	Periurethral 2 cm nodule	Resection	Not performed
Blandamura et al 11	F	26	Painful vulvar nodule	Periurethral 5 mm nodule	Resection	SMA(+), vimentin(+)
Malowany et al 12	F	61	Postmenopausal vaginal bleeding	Periurethral/anterior vaginal wall mass with focal ulceration	Wedge biopsy	Vimentin(+), desmin(+), calponin(+)
He et al 13	M	42	Tender urethral mass	1 cm mass in anterior urethra	Resection	SMA(+), CD31(+)
Ramsay et al (this article)	M	56	Painful penoscrotal nodule	1.5 cm nodule arising from right ventral aspect of anterior urethra	Resection and BMG urethroplasty	SMA(+), CD31(+)

SMA, smooth muscle actin; BMG, buccal mucosal graft.

He et al published the first case of glomus tumour in a male urethra.¹³ Similarly to the three cases in women, this patient was treated with surgical excision, but did not required further reconstruction. In our case, the tumour was closely abutting the ventral aspect of the urethra, causing noticeable external compression of the urethral mucosa on both MRI and urethrocystoscopy. He subsequently underwent urethroplasty with BMG reconstruction. In our opinion, it is mandatory to discuss possible reconstruction options with the patient prior to the surgery in any case of periurethral/urethral mass, and to ensure that a skilled reconstructive surgeon is available if a complex reconstruction is eventually required.

Recurrence rates of 4%–50% have been reported after surgical resection of glomus tumours, with incomplete excision being a significant influencing factor.²⁰ Follow-up is usually recommended to monitor for recurrence, but ideal surveillance modality or schedule have not been established. Given the very minimal data available on periurethral/urethral glomus tumours and their benign nature, we believe symptomatic follow-up to be sufficient, but that imaging should be considered in doubtful cases.

In conclusion, although extremely rare, glomus tumours must be acknowledged in the differential diagnosis of periurethral/urethral masses, and their diagnosis could potentially drastically change further management.

Learning points.

• Urethral masses, including glomus tumours, are rare and often represent a diagnostic challenge.

• Imaging should be considered in the investigation of urethral masses of unknown origin.

• Reconstructive options should be discussed with patients undergoing urethral mass resection, and skilled reconstructive urologists should be available for such surgeries.

• Teamwork and discussion with colleagues is essential in the management of complex, unusual cases, and ultimately lead to better patient care.