The utility of electron microscopy in cytopathology

Our plain-English summary of The utility of electron microscopy in cytopathology, by D. Etit, M. Selig, W.C. Faquin, et al (Ultrastructural Pathology, 2010).

The study

• Authors: D. Etit, M. Selig, W.C. Faquin, M.B. Pitman, R.H. Tambouret, J. Misdraji, G. Petur Nielsen
• Journal: Ultrastructural Pathology
• Published: 2010;34(5):252-9
• Read it: PubMed · Publisher

Abstract

Background: The use of ultrastructural analysis in the diagnostic work-up of histologic specimens has been well studied but less is known about the utility of electron microscopy (EM) in cytopathology.

Design: 149,006 non-gynecologic cytology cases at the Massachusetts General Hospital between the years 1993 and 2006 were searched to identify those in which material had been submitted for EM. Cytologic and EM diagnoses were correlated with available histologic diagnoses. The results were put into one of three categories: confirmatory, diagnostic, or insufficient material for diagnosis (IMFD).

Results: Material for EM was obtained from 178 cytology cases that included 131 fine-needle aspirates (FNA) and 47 exfoliative specimens. EM provided additional diagnostic information beyond that offered by cytologic examination alone in 32% of cases, and in 48% of cases EM confirmed the cytologic findings. Insufficient material and discrepant results were noted for EM evaluation in 19% of cases and in 1% cases respectively. EM was most useful when applied to FNAs for subclassifying tumors as epithelial or mesenchymal (45.6%), for the diagnosis of non-neoplastic processes (15.7%) such as alveolar proteinosis and amyloidosis, and for the identification of microorganisms (12.2%). In our study, although EM was infrequently applied to exfoliative specimens to distinguish mesothelioma from adenocarcinoma, it proved to be very useful in this setting.

Conclusion: When adequate material is obtained, EM can contribute significantly to the evaluation of both FNA and exfoliative cytology cases, including the diagnosis and subclassification of epithelial and mesenchymal tumors, non-neoplastic processes, and the identification of microorganisms.

In plain English

This was a review of past cases at Massachusetts General Hospital. The authors searched 149,006 non-gynecologic cytology cases from 1993 to 2006 for those in which material had been sent for electron microscopy (EM). They found 178 patients: 131 fine-needle aspirates and 47 exfoliative specimens, such as effusions, urine and bronchial washings. The study did not look at asbestos exposure. EM added diagnostic information beyond routine cytology in 32% of patients and confirmed the cytology diagnosis in 48%. There was too little material for EM in about 24% of fine-needle aspirates and 4% of exfoliative specimens. Two exfoliative cases (4%) gave conflicting results, which the authors attributed to sampling. Among 114 tumor cases, EM confirmed the diagnosis in 56 and added information in 43. The article's abstract states that EM was used infrequently on exfoliative specimens to tell mesothelioma from adenocarcinoma but proved very useful for this. The main text gives no figures for such cases. The authors concluded that, when enough material is obtained, EM can contribute significantly to cytology diagnosis.

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 review of hospital cytology case records (single institution), correlating cytology and EM diagnoses with available histology
• Who was studied: 178 patients (131 fine-needle aspirates, 47 exfoliative specimens) identified from 149,006 non-gynecologic cytology cases at Massachusetts General Hospital, Boston, 1993 to 2006
• Exposure: Not an exposure study; no asbestos or fiber exposure was examined. The subject was electron microscopy used as a diagnostic test on cytology samples, compared with cytologic and histologic diagnoses
• Main results:
  • Across all 178 patients, EM provided additional diagnostic information beyond cytology in 32%
  • Across all 178 patients, EM confirmed the cytologic diagnosis in 48%
  • Insufficient material for EM in about 24% of fine-needle aspirate cases (31 of 131) and 4% of exfoliative specimens (2 of 47)
  • EM added diagnostic information in 33% (43) of fine-needle aspirates and 30% (14) of exfoliative samples
  • In the exfoliative group, 2 case results (4%) were discrepant between cytology and EM; the authors attributed both to sampling issues
  • Of 114 cases (64.1%) that were benign or malignant neoplasms, EM was confirmatory in 56 (49.1%), diagnostic in 43 (37.7%) and had insufficient material in 15 (13.1%)
  • In fine-needle aspirates, EM was most useful for subclassifying tumors as epithelial or mesenchymal (45.6%) and for diagnosing non-neoplastic processes (15.7%) such as alveolar proteinosis and amyloidosis
  • A dedicated fine-needle pass was the most reliable way to get enough material for EM from fine-needle aspirates
  • The article's abstract states that EM was infrequently applied to exfoliative specimens to distinguish mesothelioma from adenocarcinoma but proved very useful in this setting; the body of the article gives no case numbers for this
• The authors' conclusion: The authors concluded that EM is underused in cytology. They concluded that, when adequate material is obtained, it can contribute significantly to evaluating fine-needle aspirate and exfoliative cases, including tumor diagnosis and subclassification, non-neoplastic processes and identification of microorganisms.

Topics

Medical terms in this study, explained in our Lexicon: Cytopathology, Cytology, Aspirate, Mesothelioma, Adenocarcinoma, Mesenchymal Tumor.

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