Peritoneal malignant mesothelioma: Slippery like an eel to diagnose on cytology-case series of 3 cases

Our plain-English summary of Peritoneal malignant mesothelioma: Slippery like an eel to diagnose on cytology-case series of 3 cases, by N. Gupta, A. Soni, R. Mahajan, et al (Journal of the American Society of Cytopathology, 2022).

The study

• Authors: N. Gupta, A. Soni, R. Mahajan, P. Selhi, R. Tyagi, B. Garg, H. Kaur
• Journal: Journal of the American Society of Cytopathology
• Published: 2022;11(1):40-45
• Type of article: Case report
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: Peritoneal malignant mesothelioma is an extremely rare tumor and is a difficult diagnosis to be made on cytology alone. We report 3 cases where the cytologic features were misdiagnosed as carcinoma/lymphoma but histopathology and immunohistochemistry (IHC) established the diagnosis of malignant mesothelioma.

Clinical Details: Case 1 was a 60-year-old man with multiloculated ascites and omental caking. Peritoneal fluid was reported as malignant on cytology but was misclassified as adenocarcinoma. Case 2, a 45-year-old man with ascites and peritoneal nodularity, radiologically mimicking peritoneal carcinomatosis, was also reported positive for malignancy on ascitic fluid cytology. Fine-needle aspiration (FNAC) from omental fat revealed signet ring cells, thus misleading to cytologic diagnosis of adenocarcinoma. Case 3 was a 63-year-old man with perisplenic mass with extensive omental caking and peritoneal nodularity that was also suspected to be peritoneal carcinomatosis on radiology. FNAC smears from perisplenic mass showed sheets of plasmacytoid cells. On cytology, the differential diagnoses offered were neuroendocrine tumor or non-Hodgkin lymphoma. The diagnosis of malignant mesothelioma was established only after IHC on histopathologic sections in all these cases. None of our patients had history of prior asbestos exposure.

Conclusion: In such clinical scenarios, with radiology suggesting peritoneal carcinomatosis, the cytologic features need corroboration by IHC/fluorescence in situ hybridization on cell block or biopsy to correctly identify malignant mesothelioma and differentiate it from metastatic carcinomatous deposits and benign mesothelial proliferation.

Copyright © 2021 American Society of Cytopathology. Published by Elsevier Inc. All rights reserved.

In plain English

This article was a case series describing three men with peritoneal malignant mesothelioma, a cancer of the lining of the abdomen, seen at Dayanand Medical College and Hospital in Ludhiana, India. The authors reported that in all three, examination of loose cells (cytology) pointed to the wrong diagnosis. In a 60-year-old man, abdominal fluid was read as adenocarcinoma. In a 45-year-old man, abdominal fluid was reported as suspicious of malignancy, and a needle sample from the omentum, which showed signet ring cells, was diagnosed as mucin rich adenocarcinoma. In a 63-year-old man, a needle sample from a mass near the spleen suggested a neuroendocrine tumour or non-Hodgkin lymphoma. In each case, mesothelioma was diagnosed only after tissue examination with immunohistochemistry, which stains for specific proteins. None of the three patients had a history of prior asbestos exposure. The first patient died after two cycles of chemotherapy. The other two were reported to be doing better clinically and remained on follow-up. The authors concluded that in such misleading situations, cytology findings need confirmation by immunohistochemistry or FISH testing on cell block or biopsy material.

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 series (3 cases)
• Who was studied: Three men aged 60, 45 and 63 with peritoneal malignant mesothelioma, seen at Dayanand Medical College and Hospital, Ludhiana, Punjab, India; dates of the cases not given
• Exposure: None of the three patients had a history of prior exposure to asbestos; no fiber types or occupations described
• Main results:
  • Case 1 (60-year-old man): peritoneal fluid cytology was diagnosed as adenocarcinoma
  • Case 1: on immunohistochemistry of the excised tissue, tumour cells were positive for calretinin, WT-1, CK-5/6, vimentin, CK-7 and CD-117, and peritoneal malignant mesothelioma was diagnosed; the patient died after two cycles of chemotherapy
  • Case 2 (45-year-old man): needle aspiration of omental nodularity, with signet ring cells, was diagnosed on cytology as mucin rich adenocarcinoma
  • Case 2: omental biopsy cells were positive for CK-7, calretinin and p53, giving a final diagnosis of peritoneal malignant mesothelioma; the patient was on chemotherapy and doing better clinically
  • Case 3 (63-year-old man): needle aspiration of a perisplenic mass suggested neuroendocrine tumour or non-Hodgkin lymphoma on cytology
  • Case 3: biopsies with immunohistochemistry (positive for CK-7, WT-1, calretinin, EMA) established peritoneal malignant mesothelioma; the patient was on chemotherapy and doing better clinically
  • In all three cases, mesothelioma was diagnosed only after immunohistochemistry on tissue sections
• The authors' conclusion: The authors concluded that, in misleading clinical situations, cytology findings need corroboration with immunohistochemistry or FISH on cell block or biopsy to confirm mesothelioma and distinguish it from metastatic carcinoma and benign mesothelial proliferation

Topics

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

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Cytology, Carcinoma, Histopathology, Immunohistochemistry, Ascites, Omental Caking, Adenocarcinoma.

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