Donut sign: a unique radiological sign of cerebral metastasis in malignant mesothelioma

Our plain-English summary of Donut sign: a unique radiological sign of cerebral metastasis in malignant mesothelioma, by O. Adeyinka, A. Dower, Y. Li (BMJ Case Reports, 2022).

The study

• Authors: O. Adeyinka, A. Dower, Y. Li
• Journal: BMJ Case Reports
• Published: 2022;15(10)
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

A man in his 70s presented to the emergency department with a 3-day history of confusion and right-facial droop. He was diagnosed with stage IIIB (T4N2M0) malignant mesothelioma 6 months previously for which he was being given palliative chemotherapy. An MRI of the brain demonstrated a left parietal cerebral metastasis with unique radiological characteristics termed 'donut sign'. He underwent a craniotomy and complete macroscopic resection of the lesion with a good postoperative outcome. Mesothelioma cerebral metastases are a rarely reported clinical entity, with only a handful of case reports and case series available. On MRI they often demonstrate a distinctive thick-walled lesion, termed 'donut sign', that may be indicative of the diagnosis. Furthermore, case autopsy series suggest these metastases may be underdiagnosed in the clinical setting due to the dismal prognosis. With newer and more effective neoplastic treatment strategies emerging, there may be a rising incidence of central nervous system metastases in the future.

© BMJ Publishing Group Limited 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

In plain English

This case report from New South Wales, Australia, described one man in his 70s, a former plumber, with stage IIIB (T4N2M0) malignant lung mesothelioma diagnosed 6 months earlier. The article does not discuss asbestos exposure. He came to hospital after 3 days of confusion and a right-sided facial droop. A CT scan showed a 28 mm round, thick-walled mass in the left parietal area of the brain with swelling around it. On MRI, the lesion had a ring of even thickness around a dead (necrotic) centre, an appearance the authors called the 'donut sign'. Surgeons removed all visible tumour, and tissue analysis was consistent with malignant mesothelioma. The patient went home on day 3 after surgery. A brain MRI at 1 month showed no evidence of remaining tumour at the surgical site. At 4 weeks he had made an excellent recovery apart from occasional forgetfulness. He later received stereotactic radiosurgery and the immunotherapy drug ipilimumab. Among earlier case reports with available imaging, the authors found three of four patients with similar features. The authors concluded these brain metastases may have a unique MRI appearance, but said its significance is not yet known.

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 (single patient), with a brief review of earlier case reports
• Who was studied: One man in his 70s, a former plumber, with stage IIIB (T4N2M0) malignant lung mesothelioma diagnosed 6 months before he presented with brain symptoms; treated at hospitals in New South Wales, Australia
• Exposure: The article does not describe asbestos or any other exposure. It gives only the patient's former occupation as a plumber.
• Main results:
  • In this patient, CT of the brain showed a 28 mm, thick-walled, round left parietal mass with surrounding swelling (oedema).
  • In this patient, MRI showed the lesion's enhancing ring was uniformly thick all the way around, with a necrotic centre. The authors named this appearance the 'donut sign'.
  • The patient had a stereotactic craniotomy with complete macroscopic (all visible) removal of the tumour.
  • Tissue analysis of the removed lesion was consistent with malignant mesothelioma.
  • The patient was discharged home on day 3 after surgery.
  • A brain MRI at 1 month after surgery showed a fluid-filled cavity at the resection site with no indication of residual or recurrent disease there.
  • At 4 weeks after surgery the patient had made an excellent recovery. Apart from occasional forgetfulness, he had no neurological deficits.
  • The patient went on to receive stereotactic radiosurgery and a course of the immunotherapy drug ipilimumab.
  • In the authors' review of the literature, three of four patients from other case reports with available imaging had features resembling the 'donut sign'.
• The authors' conclusion: The authors concluded that brain metastases from mesothelioma may have a unique MRI appearance, which they termed the 'donut sign'.
• Limitations the authors state:
  • The authors stated that the exact significance of this radiological appearance is not yet known.
  • The authors stated that the biological mechanism behind the appearance is unknown. Their explanation of it is offered as a hypothesis.

Topics

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

Medical terms in this study, explained in our Lexicon: Metastasis, Mesothelioma, Palliative Care, Chemotherapy, Autopsy, Prognosis.

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