Strength and Weaknesses of Application of International Academy of Cytology Yokohama System for Reporting Breast Fine-needle Aspiration Cytopathology.

Dear Editor

International Academy of Cytology (IAC), Yokohoma system aims to establish best practice guidelines for breast fine-needle aspiration biopsy (FNAB). It proposes a standardized report with clear terminology of reporting categories, each of which has a risk of malignancy (ROM) and is linked to management options.[1]

The reporting system format begins with one of the five standard categories, followed by an assessment of cellularity, a description of key cytopathological features, or if this is not possible, a differential diagnosis with a preferred diagnosis. The five defined categories are insufficient or inadequate, benign, atypical, suspicious for malignancy, and malignant.[2]

To access the challenges and limitations of the IAC system, we carried out a retrospective analysis of breast FNAB cytology, reanalyzed it, and categorized it as per the Yokohama system. Findings were compared to different forms of reporting terms used and clinical outcomes along with histo-cytological correlation.

A total of 202 breast FNAB were classified under category - 1-8.91% (n = 18); 2-54.45% (n = 110); 3-0.91% (n = 1); 4-1.48% (n = 2); 5-34.15% (n = 69). 3.9% (n = 8) were reported as inadequate with a descriptive report. According to IAC criteria, this number increased to 18. Most variable category was “benign.” Ninety-four (85.45%) cases lacked clear statement regarding “absence of malignancy.” All suspicious and atypical cases turned out to be malignant on further biopsy. Histopathological examination was performed in 54 cases with significant correlation (P < 0.001).

Our findings reinforce the significance of the Yokahama grading system in providing a standardized cytological diagnosis. It helps to remove multiple terminologies used and benefits clinicians. These are supported by literature, which shows probabilistic categories proposed by the IAC system, which stratify the risk and allow management algorithms to be correlated.[13]

We however would like to address an issue. There was a significant overlap between categories 3 and 4.

Category 3 “atypical” is “presence of cytological features seen predominantly in benign processes/lesions, but with addition of some features that are uncommon in benign lesions, and which may be seen in malignant lesions. These include single intact cell dispersal and nuclear enlargement or pleomorphism, high cellularity, necrosis, and complex architectural features that could suggest micropapillary or cribriform proliferations.”[2]

Category 4 “suspicious of malignancy” is “presence of some cytomorphological features which are usually found in malignant lesions, but with insufficient malignant features, either in number or quality to make a definitive diagnosis of malignancy.”[2]

This broadly implies that for diffuse cellular changes accompanied by calcifications or other atypical features, one must diagnose as 4 instead of 3. This leads to wide inter-observer variability. If someone gives inappropriate weighting to usual atypical features, while not recognizing the overall diagnostic pattern, it will lead to a higher “suspicious” rate. Limitations in specimen technical quality also play a significant role.[1]

Management in both categories however requires confirmation by a definitive method at some stage. In our study, there was one atypical and two cases of suspicious of malignancy, which were all, advised core needle biopsy, and all eventually turned out to be malignant on histopathology. Partly similar findings were observed by Wong et al. where 2 of atypical cases, Agarwal et al. where 5 of their atypical cases were malignant on histopathology as also seen in studies conducted by Montezuma et al. and Rosa et al. where 35 of 270 and 58 of 280 atypical cases turned out to be malignant on histopathological examination, respectively.[1345] Since both categories clinically represent lesions, which require follow-up compared to cytological benign lesions, we propose a merger of both “atypical” and “suspicious of malignancy” categories for a more simplified approach to their diagnosis, especially for new cytopathologists to avoid inter-observer variation.

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Nil.

Conflicts of interest

Dr. Isha Makker and Dr. Preeti Agarwal have equal contributions to the manuscript. All the authors are in view that the present study raises an important cytology question.

Data availability

All data generated or analyzed during this case are included in this article. Further enquiries can be directed to the corresponding author.