Malignant mesothelioma of the tunica vaginalis testis initially misdiagnosed as a benign testicular hydrocele: a case report

Our plain-English summary of Malignant mesothelioma of the tunica vaginalis testis initially misdiagnosed as a benign testicular hydrocele: a case report, by C. Zhang, H. Su, L. Guo, et al (Frontiers in Oncology, 2026).

The study

• Authors: C. Zhang, H. Su, L. Guo, Z. Li, J. Wang, J. Chen, G. Wang
• Journal: Frontiers in Oncology
• Published: 2026;16:1902555
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: To improve the clinical understanding, diagnostic accuracy, and therapeutic management of mesothelioma of the tunica vaginalis testis.

Methods: We present a case of mesothelioma of the tunica vaginalis in a patient recently admitted to our institution. The clinical characteristics, histopathological features, and therapeutic modalities used are described. FAPI PET/CT was applied as an adjunctive diagnostic tool for preoperative surgical planning. A narrative review of the relevant literature was conducted to discuss current diagnostic approaches, treatment options, and prognostic outcomes.

Results: Postoperative histopathological examination revealed an epithelioid mesothelioma of the left testis. The tumor infiltrated the visceral tunica vaginalis and extended outward into the subcutaneous fibrous connective tissue of the scrotum. The infiltration also extended through the parietal tunica vaginalis to the tunica albuginea and involved the smooth muscle of the spermatic cord and the pampiniform venous plexus, with formation of a tunica vaginalis cyst. The adjacent testicular parenchyma and epididymis were not involved, and the spermatic cord surgical margin was free of malignancy.

Conclusion: Mesothelioma of the tunica vaginalis is a rare malignancy with distinctive histopathological features. Because its clinical presentation resembles that of hydrocele, it is readily misdiagnosed. This case underscores the need to maintain a high index of suspicion when evaluating patients who present with hydrocele. The absence of recurrence at the limited 2-month follow-up does not permit any conclusion regarding disease control, cure, or recurrence, and prolonged surveillance is required. The efficacy and necessity of postoperative adjuvant treatment-including chemotherapy, radiotherapy, and targeted therapy-warrant further validation in prospective studies.

Copyright © 2026 Zhang, Su, Guo, Li, Wang, Chen and Wang.

In plain English

This case report described a 37-year-old man treated at Hebei General Hospital, China, in 2026 for mesothelioma of the tunica vaginalis, the lining around the testis. His painful left scrotal swelling was first thought on ultrasound to be a benign fluid collection (hydrocele), and a hydrocele operation was done at another hospital. The authors' pathology department found the removed tissue highly suggestive of low-grade epithelioid mesothelioma. A FAPI PET/CT scan showed mild uptake in the left scrotum and no signs of lymph node or distant spread. His left testis was then removed. Pathology confirmed epithelioid mesothelioma that had grown into nearby structures, including the spermatic cord, but not the testis itself or the epididymis. The spermatic cord margins were tumor-free. A recommended genetic test was declined for financial reasons. At 2 months there was no sign of recurrence, which the authors said is too short to judge the outcome. The article does not say whether he had asbestos exposure. The authors concluded that doctors should keep a high index of suspicion in patients with hydrocele.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report of a single patient, with a narrative discussion of the published literature
• Who was studied: One 37-year-old man with left scrotal swelling, treated at Hebei General Hospital, Shijiazhuang, China, in February to March 2026
• Exposure: Not reported. The article does not state whether this patient had any asbestos exposure. The asbestos figures in the discussion come from other studies.
• Main results:
  • The patient's scrotal swelling was initially judged on ultrasound to be a left testicular hydrocele, and a hydrocelectomy was performed at another hospital.
  • On review of the referring hospital's staining results, the authors' pathology department found the tunica vaginalis lesion highly suggestive of a low-grade epithelioid mesothelioma.
  • 68Ga-FAPI PET/CT showed a soft-tissue area of about 40 x 38 x 31 mm in the left scrotum with mild, uneven uptake (SUV max 3.2). No FAPI-avid lymph nodes and no distant metastatic lesions were identified.
  • A radical left orchiectomy was performed. The removed specimen measured about 35 mm x 25 mm x 20 mm.
  • Pathology confirmed epithelioid mesothelioma of the left testis extending into the tunica albuginea, spermatic cord smooth muscle and pampiniform plexus. The testicular parenchyma and epididymis were not involved, and the spermatic cord margins were tumor-free. The authors described this as locally advanced disease.
  • CDKN2A/p16 FISH testing was not performed because the patient and his family declined it for financial reasons.
  • At the 2-month follow-up there was no clinical or radiological evidence of recurrence. The authors stated that this interval is too short to assess oncological control.
• The authors' conclusion: The authors concluded that this rare malignancy is readily mistaken for hydrocele, so a high index of suspicion is needed in patients with hydrocele. They also stated that the 2-month follow-up allows no inference about long-term control or recurrence.
• Limitations the authors state:
  • The two-month follow-up is too short to draw definitive conclusions about long-term outcomes.
  • The FAPI PET/CT was done only 3 weeks after the first operation. The mild scrotal uptake likely reflected both residual tumor and post-surgical healing, so it should be interpreted with caution.
  • The pathology report did not document the specific distance from the tumor to the negative margin.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Tunica Vaginalis, Hydrocele, Epithelioid, Spermatic Cord, Parenchyma, Epididymis, Chemotherapy.

Related studies

• Mesothelioma of the Tunica Vaginalis Testis Initially Treated as Hydrocele: A Case Report — J.I. Hori, S. Yamaguchi, et al. (2026)
• Pre-operative diagnosis of malignant mesothelioma of tunica vaginalis testis by hydrocele fluid cytology — S.C. Gupta, A.K. Gupta, et al. (1998)
• Malignant mesothelioma of the tunica vaginalis testis: A rare cause of hydrocele — M. de Sá Barrêto Callou Peixoto, M.K. Bernardo Soares, et al. (2022)
• Malignant Epithelioid Mesothelioma of the Tunica Vaginalis Testis Presenting as Hydrocele in a Kidney Transplant Recipient — B.M. Behers, C.W. Guske, et al. (2024)
• When a hydrocele is more than a hydrocele: Warning symptoms and signs of malignant mesothelioma of the tunica vaginalis testis — J. Cornfield, M. Lee, et al. (2026)
• Analysis of mutations of PARP1, RNF213, PAX8, KMT2C, MTRR in malignant mesothelioma of testicular tunica vaginalis testis — A. Kowalik, A. Wincewicz, et al. (2020)

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