Mesothelioma of the tunica vaginalis: a series of eight cases with uncertain malignant potential

Our plain-English summary of Mesothelioma of the tunica vaginalis: a series of eight cases with uncertain malignant potential, by F. Brimo, P.B. Illei, J.I. Epstein (Modern Pathology, 2010).

The study

• Authors: F. Brimo, P.B. Illei, J.I. Epstein
• Journal: Modern Pathology
• Published: 2010;23(8):1165-72
• Type of article: Case report
• Cited by: 50 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Well-differentiated papillary mesotheliomas have rarely been reported to involve the testis tunica vaginalis. While the classic histology of the originally described well-differentiated papillary mesotheliomas consisted of papillae lined by a single layer of bland cuboidal cells, more complex architectural patterns have been described. This report details our experience with eight paratesticular mesotheliomas that span the histological spectrum from classic well-differentiated papillary mesotheliomas to those with more complex patterns. We attempt to determine whether there are prognostic or immunohistochemical differences between these lesions and 28 diffuse malignant mesotheliomas. All cases had papillary/tubulopapillary in addition to more complex architectures (cribriform, condensed) and none showed evidence of invasion. Mitotic figures were present in seven cases and averaged 2.1 mitosis per 50 h.p.f. All cases showed <or=1% of positive cells staining for Ki-67 and p53, and only one case stained positive for GLUT-1 in comparison with 50% positivity for GLUT-1 in diffuse mesotheliomas. Of five patients with follow-up information of more than 1 year, three patients were alive at 2, 3 and 9 years, and two died of unknown causes at 5 and 47 years, suggesting that these lesions behave more indolently than typical malignant mesotheliomas of the tunica vaginalis. If these cases were diffuse malignant mesotheliomas, one would have expected at least some of the patients to have died of disease within a couple of years after diagnosis. However, detailed and long-term follow-up were not sufficiently available to reach definitive conclusions on the true biological behavior of these tumors. The morphological continuum noted between our cases and classic well-differentiated papillary mesotheliomas, combined with their immunohistochemical profile and indolent behavior, contrasts with that of diffuse malignant mesotheliomas. We propose that these tunica vaginalis mesotheliomas, which are more complex than the classic well-differentiated papillary mesotheliomas, and yet are not overtly histologically malignant, be classified as 'mesotheliomas of uncertain malignant potential'.

In plain English

This was a pathology case series of eight mesotheliomas of the tunica vaginalis, the lining around the testis. The cases came from one author's consultation files and fell between classic well-differentiated papillary mesothelioma and diffuse malignant mesothelioma. The authors compared tissue staining in these cases with 28 diffuse malignant mesotheliomas from a tissue sample collection of pleural-based mesotheliomas. Patients were 34 to 73 years old. Detailed asbestos exposure histories were not available. None of the eight tumors showed clear signs of invasion. Mitoses were seen in seven of eight cases. One of the eight cases stained positive for the marker GLUT-1, compared with 50% of the diffuse malignant mesotheliomas. Of five patients followed for more than a year, three were alive at 2, 3 and 9 years, and two died of unknown causes at 5 and 47 years. The authors noted that follow-up was too limited to draw definite conclusions about how these tumors behave. They proposed that such tumors be classified as "mesotheliomas of uncertain malignant potential".

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: Retrospective pathology case series with an immunohistochemical (tissue staining) comparison group
• Who was studied: Eight men with paratesticular (tunica vaginalis) mesotheliomas, aged 34 to 73 years (mean 52.5), from the consultation files of one author at Johns Hopkins, Baltimore. The comparison group was 28 diffuse malignant mesotheliomas from a tissue microarray of pleural-based mesotheliomas. No study period was given.
• Exposure: Asbestos exposure was not studied; the authors state that detailed asbestos exposure history was unavailable
• Main results:
  • In seven of the eight patients, the first sign of disease was a hydrocele (fluid around the testis); one patient presented with a scrotal mass
  • None of the eight tumors showed clear-cut invasion of the tissue beneath the mesothelium
  • Mitotic figures (dividing cells) were present in seven of the eight tunica vaginalis cases, averaging 2.1 per 50 high-power fields (range 0 to 6). No case had atypical mitoses or necrosis.
  • GLUT-1 staining was positive in one of the eight tunica vaginalis cases (12.5%), very focally (1% of cells)
  • GLUT-1 staining was positive in 50% of the 28 diffuse malignant mesotheliomas
  • Ki-67 labeled 1% or fewer of cells in all eight tunica vaginalis cases
  • p53 was negative in five of the eight tunica vaginalis cases and stained 1% or fewer of cells in the other three. In the diffuse malignant mesotheliomas, 8 of 26 evaluable cases (31%) were positive, with a mean of 33% positive cells (range 1 to 90%).
  • Three patients had radical orchiectomy, which showed no residual disease; none of the patients received chemotherapy or radiation
  • Of five patients with more than 1 year of follow-up, three were alive at 2, 3 and 9 years, and two died of unknown causes at 5 and 47 years
• The authors' conclusion: The authors proposed that tunica vaginalis mesotheliomas that are more complex than classic well-differentiated papillary mesotheliomas, but not overtly malignant under the microscope, be classified as mesotheliomas of uncertain malignant potential
• Limitations the authors state:
  • Detailed and long-term follow-up was not available enough to reach definitive conclusions on how these tumors behave
  • Ki-67 staining could not be done on the comparison pleural mesotheliomas because there was not enough tissue
  • Some features of these tumors might be read by others as invasion and therefore as overt malignancy
  • It is unknown whether the giant cell tumor-like area seen in one case carries a worse outlook

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Tunica Vaginalis, Well-Differentiated Papillary Mesothelioma, Histology, Papillae, Testicular Mesothelioma, Tubulopapillary, Ki-67.

Related studies

• Malignant Mesothelioma of the Tunica Vaginalis Testis-A Malignancy Associated With Asbestos Exposure and Trauma: A Case Report and Literature Review — A.A. Baqui, N.A. Boire, et al. (2019)
• Mesothelioma of the tunica vaginalis testis: report of 2 cases with asbestos occupational exposure — G. Gorini, M. Pinelli, et al. (2005)
• Mesothelioma of the tunica vaginalis testis — K.J. Butnor, E.N. Pavlisko, et al. (2019)
• Preoperative cytological diagnosis of malignant mesothelioma of tunica vaginalis — A. Bandyopadhyay, S. Bhattacharya, et al. (2015)
• Well-differentiated papillary mesothelioma of tunica vaginalis testis of unknown malignant potential: Sonographic appearance — K.W.S. Ko, K.S. Tse, et al. (2018)
• Clinical Features and Outcomes of Tunica Vaginalis Mesothelioma: A Case Series From the National Institutes of Health — J.Y. An, D. Kim, et al. (2017)

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