Case report: Onychopapilloma in a patient with BAP1 tumor predisposition syndrome-a useful clinical marker?

Our plain-English summary of Case report: Onychopapilloma in a patient with BAP1 tumor predisposition syndrome-a useful clinical marker?, by E. Sjøstrøm, L.B. Ahlborn, E.V. Eliesen, et al (Familial Cancer, 2026).

The study

• Authors: E. Sjøstrøm, L.B. Ahlborn, E.V. Eliesen, K. Wadt, U. Lei, A. Byrjalsen
• Journal: Familial Cancer
• Published: 2026;25(2)
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

The BAP1 gene encodes a tumor suppressor protein implicated in BAP1 tumor predisposition syndrome (BAP1-TPDS), a hereditary condition associated with an increased risk of uveal and skin melanoma, mesothelioma, and renal cancer. In this case report, we describe a male patient diagnosed with mesothelioma carrying a germline BAP1 variant. The patient exhibited severe nail abnormalities affecting all ten fingernails and several toenails. To our knowledge, the association between onychopapilloma and pathogenic germline BAP1 variants has only been reported once in the literature. The patient had experienced nail abnormalities since adolescence. Based on these findings, we propose that polydactylous onychopapilloma may serve as a clinical marker of BAP1-TPDS in otherwise asymptomatic individuals, and could potentially aid in early identification of at-risk carriers.

In plain English

This case report described a 63-year-old man diagnosed with epithelioid mesothelioma after he developed cough, right-sided chest pain and coughing up blood. Scans showed a 10.2 cm tumor in the right upper lung lobe that had spread to the pleura, pericardium and lymph nodes. Occupational medicine doctors judged asbestos exposure likely because he worked as an electrician. No fiber type was reported. After three years of treatment, including 15 cycles of chemotherapy, the disease progressed. Genetic testing of the tumor and his normal tissue found an inherited (germline) BAP1 variant classified as disease causing. His adult son and daughter both carried it. He had had abnormal fingernails since his teenage years, with toenail changes about 10 years later, and fungal tests were negative. Dermatologists found involvement of all fingernails and several toenails, consistent with onychopapilloma, a benign growth of the nail. The authors proposed that onychopapilloma affecting many nails may be a clinical marker of BAP1 tumor predisposition syndrome in people without other signs. The report describes one patient.

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
• Who was studied: One 63-year-old man with mesothelioma, seen at hospital departments in the Copenhagen area, Denmark (per the author affiliations). His adult son and daughter were also tested.
• Exposure: Asbestos exposure was judged likely by occupational medicine because of his work as an electrician. No known asbestos exposure was reported in private settings. No fiber type or dose was given. The study's focus was a germline BAP1 variant, c.178C > T, p.(Arg60Ter).
• Main results:
  • In the patient, PET-CT showed a 10.2 cm tumor in the right upper lung lobe with spread to the pleura, pericardium and lymph nodes. Biopsy confirmed epithelioid mesothelioma.
  • In the patient, the disease progressed despite three years of treatment covering 15 cycles of different chemotherapies.
  • In the patient, sequencing identified a germline BAP1 nonsense variant, c.178C > T, p.(Arg60Ter), VAF 67%. It was classified as pathogenic (Class 5).
  • Both of the patient's adult children (a son and a daughter) tested positive for the germline variant.
  • In the patient, the dermatology assessment found involvement of all fingernails and several toenails. The changes were consistent with a clinical diagnosis of onychopapilloma, a benign neoplasm of the nail.
  • The patient reported fingernail changes since his teenage years. Toenail involvement became evident about 10 years later.
  • Multiple tests of the patient for fungal infection were all negative.
  • The patient's son had nail dystrophy in a single fingernail only. The daughter had no nail abnormalities.
• The authors' conclusion: The authors concluded that this case underscores the need for greater awareness of subtle skin and nail signs that may be early indicators of BAP1 tumor predisposition syndrome in carriers without other symptoms. They proposed that onychopapilloma affecting many nails may serve as such a marker.

Topics

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

Medical terms in this study, explained in our Lexicon: BAP1 Tumor Predisposition Syndrome, BAP1, Mesothelioma.

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• Expanding the clinical phenotype of hereditary BAP1 cancer predisposition syndrome, reporting three new cases — R. Pilarski, C.M. Cebulla, et al. (2014)
• High frequency and unique subtypes of meningioma in patients with BAP1 tumor predisposition syndrome — K.A. Ramsey, L. Byrne, et al. (2026)
• Histomorphologic spectrum of BAP1 negative melanocytic neoplasms in a family with BAP1-associated cancer susceptibility syndrome — Z. Marušić, M. Buljan, et al. (2015)
• Comprehensive review of BAP1 tumor predisposition syndrome with report of two new cases — K. Rai, R. Pilarski, et al. (2016)
• Malignant Peripheral Nerve Sheath Tumor in a Patient With BAP1 Tumor Predisposition Syndrome — M.C. Kaszuba, J.S. Pulido, et al. (2018)

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