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Recommendations for testing of cytology specimens

Recommend-ations for testing of cytology specimens

Dr. Bui, MD, PhD, discusses the advantages and disadvantages of using cytology samples for HER2 IHC testing in breast cancer.

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Marilyn Bui

MD, PhD

Marilyn Bui, MD, PhD, is a Senior Member in the Department of Pathology and the Scientific Director of the Analytic Microscopy Core at the Moffitt Cancer Center in Tampa, FL. She is also a Professor and the Director of the Cytopathology Fellowship Program at the University of South Florida Morsani College of Medicine. In this article, Dr. Bui, MD, PhD, discusses the advantages and disadvantages of using cytology samples for HER2 IHC testing in breast cancer, particularly focusing on the impact of pre-analytic variables on the reliability of test results.

What are cytology specimens? How does processing of cytology specimens differ from tissue?

Cytology specimens, in general, are more highly dispersed cells, such as those that occur in liquid as well as samples from minute tissue fragments, such as in a fine-needle aspiration biopsy.¹ Oftentimes, cytology specimens, such as a fine needle aspirate or exfoliative fluid sample, are submitted for HER2 IHC testing. The cell blocks are typically prepared within 24 hours after the procedure is performed, but there is no standardized method used to generate the cell block pellets before subjecting them to formalin fixation and paraffin embedding.^1,2 In contrast, the handling and processing of core needle biopsies or breast tissue resections are standardized in the 2023 ASCO-CAP clinical practice guidelines.²

“Various cell block methods may result in variation in cellularity and unforeseen impact on HER2 testing.”¹

In addition, the tumor cells in the cell block may not maintain the architecture of the tumor that is seen in histological tissue samples. Since the main purpose of cytology is to identify metastatic or recurrent breast cancer, the samples received at cytology practices are typically of later or higher stages of the disease.

What are the most important factors to consider when handling cytology specimens?

It is important to keep in mind that metastatic breast cancer samples must be tested for prognostic and predictive biomarkers, such as HER2, as per the ASCO-CAP guidelines.³ During the collection of samples, efforts should be made to generate adequate cell blocks and to use fixatives such as formalin.¹ Though there is no standardized procedure set out in clinical guidelines, a good general practice consensus deems 100 tumor cells to be adequate for evaluation.⁴ Per ASCO-CAP guidelines, the optimal tissue handling requirements include: (1) time from tissue acquisition to fixation should be as short as possible; (2) samples for HER2 testing are fixed in 10% neutral buffered formalin for 6-72 hours; and (3) cytology specimens must be fixed in formalin.²

What are the advantages and disadvantages of HER2 testing on cytology specimens?

“Cytology is a rapid, inexpensive, and less invasive alternative to surgically obtaining samples for evaluation of HER2 status in metastatic or recurrent breast cancer.”^1,4

The cytology samples are freshly collected with dispersed tumor cells that are more accessible to antibody labeling.⁵ Due to its inherent limited cellularity, cell blocks are often inadequate for diagnostic testing and therefore hinder patient management.¹ Some studies have shown that cell blocks from primary or metastatic breast cancer are reliable for HER2 IHC testing, while other studies have questioned the reliability of cytological specimens for HER2 testing due to unstable staining (Figure 1).^4-8 Furthermore, the role of using liquid-based cytology samples for HER2 testing remains undefined.

Figure 1. An example of a HER2-negative (1+) case showing consistent results between the CB (a) and histological specimen (b).⁴

What do the 2023 ASCO-CAP guidelines recommend for HER2 testing on cytology specimens? Do you have any additional practical recommendations from your own practice?

The 2023 ASCO-CAP guidelines recommend HER2 testing of cytology specimens must be done on specimens that are fixed in formalin.² To ensure accurate and reproducible reporting of HER2 IHC results using cell blocks, it is important to address both the pre-analytic factors affecting proper HER2 testing alongside other relevant issues.⁸ Strict adherence to the 2023 ASCO-CAP HER2 testing and reporting guidelines (the same as those used for histological sections), adequate training, and intradepartmental consensus on HER2-low cases are recommended.

What are your key takeaways for the pathology community to optimize HER2 testing on cytology specimens?

“For cellular and appropriately prepared cell block material, HER2 IHC testing can be performed with reliable results, similar to those using histological samples.”

The concordance of HER2 IHC results between cell block and histological specimens is more consistent and robust for HER2-positive tumors when compared to other HER2 expression groups. Precautions should be taken to ensure adequate quality cellularity of the cell block material. Practice standards have yet to be determined for testing on HER2-low using cytological specimens.

ASCO, American Society of Clinical Oncology; CAP, College of American Pathologists; CB, cell block; HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry.

1. Bui MM and Pantanowitz L. Monogr Clin Cytol. 2020;25:6-18. 2. Wolff AC, et al. Arch Pathol Lab Med. 2023;147(9):993-1000. 3. Van Poznack C, et al. J Clin Oncol. 2015;33(24):2695-2704. 4. Nishimura R, et al. Diagn Cytopathol. 2016;44(4):274-279. 5. Bueno Angela SP, et al. Cytopathol. 2013;24:26-32. 6. Beatty BG, et al. Am J Clin Pathol. 2004;122:246-255. 7. Kumar SK, et al. Cytopathol. 2012;23:181-186. 8. Nishimura R, et al. Acta Cytol. 2018;62(4):288-294.

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Recommendations for testing of cytology specimens

Recommend-ations for testing of cytology specimens

Marilyn Bui

MD, PhD

What are cytology specimens? How does processing of cytology specimens differ from tissue?

What are the most important factors to consider when handling cytology specimens?

What are the advantages and disadvantages of HER2 testing on cytology specimens?

Figure 1. An example of a HER2-negative (1+) case showing consistent results between the CB (a) and histological specimen (b).⁴

What do the 2023 ASCO-CAP guidelines recommend for HER2 testing on cytology specimens? Do you have any additional practical recommendations from your own practice?

What are your key takeaways for the pathology community to optimize HER2 testing on cytology specimens?

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Unusual staining pattern: Basolateral staining in micropapillary carcinoma

In this article, Dr. Jaffer details the interpretation of biomarker testing in invasive micropapillary carcinomas.

Decalcified bone specimen: Processing procedures

In this article, Dr. Wei discusses the use of bone specimens as samples for HER2 IHC in metastatic breast cancer.

Impact of pre-analytic variables on HER2 IHC results

In this article, Dr. Khoury reviews several different pre-analytic variables and their impact on HER2 IHC testing.

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Recommendations for testing of cytology specimens

Recommend-ations for testing of cytology specimens

Marilyn Bui

MD, PhD

What are cytology specimens? How does processing of cytology specimens differ from tissue?

What are the most important factors to consider when handling cytology specimens?

What are the advantages and disadvantages of HER2 testing on cytology specimens?

Figure 1. An example of a HER2-negative (1+) case showing consistent results between the CB (a) and histological specimen (b).4

What do the 2023 ASCO-CAP guidelines recommend for HER2 testing on cytology specimens? Do you have any additional practical recommendations from your own practice?

What are your key takeaways for the pathology community to optimize HER2 testing on cytology specimens?

Explore more Spotlight Series

Unusual staining pattern: Basolateral staining in micropapillary carcinoma

In this article, Dr. Jaffer details the interpretation of biomarker testing in invasive micropapillary carcinomas.

Decalcified bone specimen: Processing procedures

In this article, Dr. Wei discusses the use of bone specimens as samples for HER2 IHC in metastatic breast cancer.

Impact of pre-analytic variables on HER2 IHC results

In this article, Dr. Khoury reviews several different pre-analytic variables and their impact on HER2 IHC testing.

Quick Links

Breast Cancer Links

Gastric Cancer Links

About Us

Legal

What is a Daiichi Sankyo Company or AstraZeneca authorized person?

Figure 1. An example of a HER2-negative (1+) case showing consistent results between the CB (a) and histological specimen (b).⁴