Malignant mesothelioma of the tunica vaginalis: A case report and comprehensive literature review

Abstract

Malignant mesothelioma of the tunica vaginalis testis (MMTVT) is an exceedingly rare neoplasm, representing <1 % of all mesothelioma cases. We report a 64-year-old male with prolonged occupational asbestos exposure presenting with a chronic hydrocoele. Hydrocoelectomy revealed abnormal tunica vaginalis tissue, prompting radical orchiectomy. Histology confirmed MMTVT. Subsequent hemiscrotectomy with cord excision and inguinal lymph node dissection was performed and he remains disease free on follow up. Integrated with the largest body of literature available, this case highlights the need for heightened clinical suspicion in chronic hydrocoele with asbestos exposure, and the role of radical surgery as the cornerstone of treatment.

Highlights

• •Malignant mesothelioma of the tunica vaginalis testis (MMTVT) is exceedinglyrare and often mimics benign hydrocoele, delaying diagnosis.
• •Chronic hydrocele in patients with asbestos exposure should prompt suspicion for underlying malignancy.
• •Radical inguinal orchiectomy with hemiscrotectomy remains the cornerstone of MMTVT treatment.
• •Despite complete resection, prognosis in MMTVT remains guarded, with median survival around two years.
• •Multicentre registries and molecular studies are needed to refine prognostic markers and explore novel systemic therapies.

1. Introduction

Malignant mesothelioma most commonly arises in the pleura and peritoneum. The tunica vaginalis testis is an exceptionally rare site, accounting for <1 % of all cases.¹ Since the first description by Barbera and Rubino in 1957, just under 300 cases have been documented worldwide.² Owing to its rarity, management strategies are based on case reports, small series, and systematic reviews. The condition often mimics benign hydrocoele or scrotal pathology, delaying diagnosis.

We present a case of MMTVT from our unit, followed by a comprehensive review of the literature. Our aim is to contextualise this case within the broader evidence base and to highlight current challenges in diagnosis, treatment, and prognosis.

2. Case presentation

A 64-year-old otherwise healthy man presented with a seven-year history of progressive left-sided hydrocoele. He reported decades of occupational exposure to asbestos while working as a painter on asbestos-containing roofs. He denied systemic symptoms. Clinical examination was consistent with a left-sided hydrocele. Routine laboratory tests, including full blood count and renal function, were normal. Ultrasonography confirmed a complex, septated left hydrocoele without suspicious intratesticular nodules or masses.

He was scheduled for left hydrocoelectomy. Intraoperatively, the tunica vaginalis and testis appeared grossly abnormal with an inflammatory character, prompting conversion to radical orchiectomy with excision of the tunica. Histopathology demonstrated atypical mesothelial proliferation (Fig. 1) exhibiting a papillary and tubular architecture (100 % epitheloid morphology) invading the tunica vaginalis (Fig. 2, Fig. 3). Immunohistochemistry exhibited expression of CK, CK-5, Calretinen and WT1; consistent with a diagnosis of malignant epitheloid mesothelioma.

Fig. 1.

Hydrocele with mesothelioma in the wall (bottom left corner).

Fig. 2.

Mesothelioma seen invading the hydrocele wall.

Fig. 3.

Mesothelioma with papillary and tubular components.

Staging CT of the chest, abdomen, and pelvis showed no metastatic disease. The patient subsequently underwent completion left hemiscrotectomy with cord excision and left inguinal lymphadenectomy. Recovery was uneventful, and final pathology confirmed no residual disease and no nodal involvement. He remains disease-free at follow-up (18 months) and has been committed to surveillance.

3. Discussion

3.1. Epidemiology

MMTVT is extremely rare. In a SEER registry analysis of 52 cases over four decades, the incidence was estimated at 0.7 % of all male mesotheliomas, with a median age of 58 years.¹ A more recent systematic review by Stella et al.² summarised 289 cases between 1982 and 2024, reporting a median age of 62 years (range 6–93). Our case is consistent with this age profile.

3.2. Risk factors

Asbestos exposure is implicated in approximately one-third of cases, although its causal link remains debated.³ Other risk factors include long-standing hydrocoele, chronic inflammation, trauma, radiation, and rarely, cryptorchidism.⁴ Our patient had both asbestos exposure and a prolonged history of hydrocoele.

3.3. Clinical presentation

Patients typically present with hydrocoele or scrotal swelling, often misdiagnosed as benign pathology.² Pain is less common. Notably, unusual presentations include paraneoplastic deep vein thrombosis⁵ and cutaneous metastases.⁶

3.4. Diagnostic approach and pitfalls

Ultrasonography is the first line imaging modality but is frequently non-specific, often showing a complex hydrocoele, thickened tunica vaginalis, septations, or small paratesticular nodules.⁷ The differential diagnoses include chronic haematocele, long-standing hydrocoele with fibrosis, adenomatoid tumour, epididymal neoplasms, sarcoma, and rarely, malignant mesothelioma. Suspicious features include nodularity, irregular vascularised plaques, or rapid recurrence of hydrocoele.

CT and MRI aid in staging.⁸ Scrotal biopsy is discouraged due to seeding risk.

3.5. Histopathology and molecular markers

Definitive diagnosis requires orchiectomy specimen histology and immunohistochemistry, with positive markers typically including calretinin, WT-1, and D2-40, and negative staining for CEA and claudin-4.⁹

Epithelioid histology predominates (60 %), followed by biphasic (22 %) and sarcomatoid (∼1 %).² Biphasic tumours are associated with poorer survival, as illustrated by Drevinskaite et al.¹⁰ Benign variants, such as well-differentiated papillary mesothelial tumour (WDPMT), must be distinguished using BAP-1 and CDKN2A testing.^11,12

There is also increasing recognition of benign and borderline lesions such as well-differentiated papillary mesothelial tumour (WDPMT), which must be distinguished from malignant mesothelioma through ancillary markers like BAP-1 and CDKN2A (Kläger et al., 2023; Tan et al., 2016). These findings have important implications for overtreatment, particularly in younger men.

3.6. Surgical management and role of lymphadenectomy

Radical inguinal orchiectomy with hemiscrotectomy is the mainstay.

The role of lymphadenectomy is debated, but occult nodal metastases have been reported in up to 60 % of patients undergoing retroperitoneal lymph node dissection.⁷

Cases described by Mrinakova et al. (2016)¹³ and Trenti et al. (2018)¹⁴ demonstrate long-term survival without adjuvant therapy, supporting the central role of surgery when negative margins are achieved. Conversely, Drevinskaite et al. (2020)¹⁰ reported rapid progression and death in a biphasic case despite chemotherapy, illustrating the poor prognosis of aggressive histological variants.

Inguinal lymphadenectomy was selected in our patient because the inguinal basin represents the first-echelon drainage site of paratesticular structures, and staging CT showed no retroperitoneal lymphadenopathy. Given the absence of proven survival benefit for upfront RPLND, its substantially higher morbidity, and the ability to pursue a staged RPLND should inguinal nodes prove positive, an inguinal approach was judged most appropriate.

3.7. Systemic therapy (evidence and limitations)

The role of adjuvant systemic therapy remains uncertain, with outcomes dictated largely by histological subtype and disease stage.

Adjuvant radiotherapy and chemotherapy (typically cisplatin–pemetrexed) have not demonstrated survival benefit.² Novel systemic therapies, including immunotherapy and targeted agents, are under investigation primarily in pleural mesothelioma but may hold promise.¹⁵

Emerging therapeutic avenues for advanced disease, including immunotherapy, bevacizumab-based regimens, and molecularly targeted therapies, have been described in pleural mesothelioma and may hold relevance for MMTVT (Mutti et al., 2018).¹⁵ However, clinical evidence in this context is lacking. Gilbert et al. (2025)⁶ have reported molecular alterations including CDKN2A and NF2 loss, suggesting that genomic profiling could guide personalised therapy in the future.

3.8. Prognosis

Prognosis remains guarded. Median overall survival is approximately 24 months.^1,2 Favourable factors include small tumour size (<4 cm), epithelioid histology, and complete surgical resection. Long-term survivors have been documented, particularly after surgery alone.^13,14

3.9. Learning points

Our case illustrates several key learning points. First, the long-standing hydrocoele in an asbestos-exposed patient should heighten suspicion for underlying malignancy. Second, early intraoperative recognition of abnormal tunica allowed timely conversion to orchiectomy, preventing inadequate excision. Third, completion hemiscrotectomy and nodal dissection ensured complete disease clearance. The absence of residual tumour and current disease-free status reflect the importance of radical surgical management. This case aligns with registry and systematic review data, reinforcing that surgery is the only proven curative modality.

Overall, our case and literature synthesis support a paradigm in which radical surgery offers the best chance of durable remission, adjuvant therapy is unproven, and systemic options remain experimental. The rarity of this tumour underscores the need for international registries and collaborative studies to better characterise prognostic factors, optimise surgical strategies, and evaluate emerging systemic approaches.

4. Conclusions

MMTVT is an uncommon but aggressive malignancy. Our case demonstrates the importance of maintaining diagnostic vigilance in chronic hydrocoele, particularly with asbestos exposure. Radical surgery remains the cornerstone of treatment. Literature review indicates limited benefit of adjuvant therapy and highlights the need for multicentre registries and translational research to inform future management.

CRediT authorship contribution statement

Joshua Tiro: Writing – review & editing, Writing – original draft. Flavio Vasconcelas Ordones: Writing – review & editing. Peter John Gilling: Writing – review & editing. Lodewikus Petrus Vermeulen: Writing – review & editing, Writing – original draft.

Declarations

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Ethics and consent

Informed consent was gained from the patient prior to the writing of this report, and local ethics committee approval obtained.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.