Cytomorphologic findings of malignant mesothelioma in FNA biopsies and touch preps of core biopsies

Our plain-English summary of Cytomorphologic findings of malignant mesothelioma in FNA biopsies and touch preps of core biopsies, by A. Paintal, K. Raparia, R. Nayar (Diagnostic Cytopathology, 2016).

The study

• Authors: A. Paintal, K. Raparia, R. Nayar
• Journal: Diagnostic Cytopathology
• Published: 2016;44(1):14-9
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Given the lack of recent literature regarding the aspiration cytology of immunohistochemically confirmed malignant mesothelioma (MM), we were interested in reviewing the experience of our institution and establishing useful morphologic criteria.

Methods: Seventeen aspiration and touch preparation specimens with a diagnosis of MM obtained between 2002-2013 were reviewed along with 20 cases of adenocarcinoma and 16 cases of squamous cell carcinoma. The utility of a number of morphologic features was evaluated.

Results: In most cases of MM, a consistent pattern emerged. Aspirates and touch preps were cellular with irregularly shaped 2 and 3 dimensional clusters. The individual cells were predominantly angulated and had dense cytoplasm with eccentric nuclei. In every case, a minority of tumor cells contained prominent microvacuoles. The chromatin pattern tended to be fine with small nucleoli. While most cases were cytologically monotonous, five cases displayed striking pleomorphism and three cases contained occasional large atypical cells. Two cases contained metachromatic background material. Features which were most useful in discriminating MM from adenocarcinoma were angulated cell shape(P = 0.0002), dense cytoplasm(P = 0.0001), and cytoplasmic microvacuoles(P = 0.0001). In our material, cases of squamous cell carcinoma were often difficult to distinguish from MM. Useful discriminatory features present in squamous cell carcinoma included ink dot nuclei(P = 0.0003), a "dirty" cystic, necrotic background (P = 0.0027) and tumor balls with peripheral spindling(P = 0.0041).

Conclusion: Most cases of MM have a consistent appearance in core biopsy touch preps and FNAs. Distinguishing MM from adenocarcinoma and squamous cell carcinoma can be facilitated by evaluating a few key morphologic features.

© 2015 Wiley Periodicals, Inc.

In plain English

This Chicago hospital study examined the microscopic appearance of malignant mesothelioma in needle samples. The authors reviewed 17 mesothelioma cases from 2002 to 2013 with touch preparations from core biopsies. Nine of these also had fine needle aspirates; sites included the pleura (7) and peritoneum (5). They compared 15 microscopic features with aspirates from 20 pulmonary adenocarcinomas and 16 pulmonary squamous cell carcinomas. Compared with adenocarcinoma, the mesothelioma cases more often had angulated cells (12 of 17 versus 2 of 20), dense cytoplasm (14 versus 1) and microvacuoles (16 versus 4). Squamous cell carcinoma was often hard to tell apart from mesothelioma. Three features appeared in squamous cell carcinoma but in none of the mesotheliomas: "ink dot" nuclei (9 of 16), a "dirty" cystic background (7) and balls of cells with peripheral spindling (6). Biphasic and sarcomatoid cases did not look specific for mesothelioma. The authors concluded that a few features reliably allow the distinction. Even with classic cytology, they considered a tissue biopsy showing infiltration of fat prudent for a definitive diagnosis. Asbestos exposure was not studied.

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 stored pathology specimens from one hospital, comparing malignant mesothelioma cases with lung adenocarcinoma and squamous cell carcinoma cases using Fisher's exact test
• Who was studied: 17 histologically and immunohistochemically confirmed malignant mesothelioma cases diagnosed 2002 to 2013 at Northwestern Memorial Hospital, Chicago, with touch preparations of core biopsies (9 also had fine needle aspirates). Sites were lung (1), mediastinum (2), adrenal gland (1), pleura (7), retroperitoneal lymph node (1) and peritoneum (5). The comparison groups were fine needle aspirates of 20 randomly selected pulmonary adenocarcinomas and 16 pulmonary squamous cell carcinomas.
• Exposure: Not studied. The article compares microscopic features of tumor cells. Asbestos exposure is mentioned only in the discussion, as a general clinical clue.
• Main results:
  • Angulated cell shape was seen in 12 of 17 mesothelioma cases versus 2 of 20 adenocarcinoma cases (P = 0.0002)
  • Dense cytoplasm was seen in 14 of 17 mesothelioma cases versus 1 of 20 adenocarcinoma cases (P = 0.0001)
  • Microvacuoles were seen in 16 of 17 mesothelioma cases versus 4 of 20 adenocarcinoma cases (P = 0.0001)
  • The authors found squamous cell carcinoma cases often difficult to distinguish from mesothelioma
  • "Ink dot" nuclei were seen in 0 of 17 mesothelioma cases versus 9 of 16 squamous cell carcinoma cases (P = 0.0003)
  • A "dirty" cystic background was seen in 0 of 17 mesothelioma cases versus 7 of 16 squamous cell carcinoma cases (P = 0.0027)
  • Balls of cells with peripheral spindling were seen in 0 of 17 mesothelioma cases versus 6 of 16 squamous cell carcinoma cases (P = 0.0041)
  • In biphasic and sarcomatoid mesothelioma cases (two of each), the appearance was malignant but not specific for or suggestive of mesothelioma
• The authors' conclusion: The authors concluded that the cytologic findings in malignant mesothelioma aspirates and touch preparations are consistent in most cases, and that a few features reliably allow distinction from squamous cell carcinoma and adenocarcinoma
• Limitations the authors state:
  • Frank keratinization was not evaluated because most cases lacked Papanicolaou-stained material
  • Aspiration cytology lacks criteria for telling apart the histologic subtypes of mesothelioma (epithelioid, biphasic, sarcomatoid)
  • The authors called it prudent practice, even when cytology looks classic for mesothelioma, to require a concurrent tissue biopsy showing infiltration of fat before making a definitive diagnosis
  • The authors considered relying on aspiration and touch preparation cytology alone most appropriate for staging and for evaluating metastases in patients already diagnosed with mesothelioma

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Cytology, Adenocarcinoma, Squamous Cell Carcinoma, Aspirate, Biopsy.

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