Fine-Needle Aspiration Biopsy Cytopathology of Breast Lesions Using the International Academy of Cytology Yokohama System and Rapid On-Site Evaluation: A Single-Institute Experience

Clinical examination, radiological imaging, and breast cytopathology with or without core needle biopsy (CNB) comprise the 3 key modalities employed for diagnosing breast lumps. These modalities aim to maximize the preoperative identification of malignancy so that early, definitive, one-stage surgery or appropriate treatment can be offered to the patient [1, 2]. As a corollary, these diagnostic procedures also aim to accurately recognize benign breast lesions and avoid unnecessary invasive investigations and anxiety to the patient [2]. For breast biopsy, fine-needle aspiration biopsy (FNAB) and CNB offer complementary advantages, and both can be utilized gainfully in different settings. The recent advances in breast cytopathology with the implementation of rapid on-site evaluation (ROSE) and the development of the International Academy of Cytology (IAC) Yokohama System for Reporting Breast FNAB Cytopathology have structured the reporting of breast cytopathology with the aim of improving cytopathology procedures, training, interpretation, and diagnosis [3, 4].

In recent years, breast cancer has become the most common malignancy in Indian women, surpassing cervical cancer. An incidence of 2,05,424 new cases of breast cancer annually is projected in India, comprising ∼29.9% of all malignancies reported in women, with 87,000 annual deaths [5, 6]. FNAB and CNB are crucial preoperative tests for diagnosing these cases. However, the accuracy of FNAB depends on several factors, including the skill and experience of the operator, the localization method used, the skill of the pathologist, and the proportion of symptomatic and nonpalpable lesions being examined [7, 8]. Since numerous sources of error can confound these procedures, it is important that the performance of breast cytopathology is regularly monitored at a center using a standardized and reproducible system [3, 4, 7]. We undertook this study to incorporate ROSE and the IAC Yokohama System into our breast cytopathology protocols, evaluating their impact on the performance of breast cytopathology versus histopathology in accurately identifying breast malignancies and providing a patient’s risk of malignancy (ROM) under various IAC categories. This afforded us the opportunity to upgrade our breast reporting, create a reproducible monitoring and auditing system, and better identify the areas that need attention for further improvement of our services.

This study was carried out at the Seth GSMC & KEM Hospital, Mumbai, India, which is a tertiary care center catering to a large population in western India. In order to evaluate the impact of ROSE and the IAC System on our breast pathology reporting, we retrieved the cytopathology data of all consecutive patients investigated for breast lesions between September 2016 and December 2018. Ethics clearance was obtained from the Institute’s Ethics Committee for retrieving and analyzing this data [EC/OA-150/2019]. The data was anonymized before undertaking analyses. All the samples had been collected from the patients for routine clinical investigation, after informed consent. An attempt was made to obtain follow-up and any, histopathology report of a biopsy or excision (if performed) in all cases; however, histopathology was available only in 624 cases.

Guided and nonguided FNAB samples were collected from enrolled patients using standard procedures. ROSE was carried out using 1% aqueous toluidine blue staining. After provisional assessment by ROSE, the slides were subjected to Papanicolaou staining for standard cytopathology reporting [8]. Air-dried slides were stained using Giemsa. Special stains like Ziehl-Neelsen, Periodic acid Schiff’s, Gomori’s methanamine silver stain, and immunocytochemistry were employed on the cytology slides wherever needed and feasible.

Breast cytopathology reporting with and without ROSE, we used the diagnostic categories recommended by the IAC Yokohama System for Reporting Breast FNAB Cytopathology [1, 3]: insufficient, benign, atypical, and suspicious for malignancy and malignant. The histopathology diagnoses were broadly categorized under nonrepresentative, benign, indeterminate, in situ, and malignant, as has been reported previously [9]. Nonrepresentative histopathology included cases where there was insufficient material to reliably diagnose the lesions. Benign histopathology included breast abscess, fibroadenoma, fibrocystic changes, intraductal papilloma, scar tissue, etc. The indeterminate group included atypical fibroepithelial lesions, including phyllodes tumor, atypical ductal hyperplasia, etc. The in situ group included cases where at least one focuses of in situ pathology in the form of ductal carcinoma in situ or lobular carcinoma in situ was observed. Finally, the malignant histopathology group included cases of invasive carcinoma of no special type, medullary carcinoma, mucinous carcinoma, lobular carcinoma, and non-Hodgkin’s lymphoma.

Descriptive statistics were used to describe the patient cohort. Confusion matrices and heatmaps were computed to compare how well cytopathology (with and without ROSE) predicted the diagnostic categories of breast lesions against those assigned by histopathology. χ² test was used to compare the performance of cytopathology with and without ROSE, across different IAC categories. Performance metrics, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, and area under the receiver operating characteristic curve (AUC) were computed to compare the performance of cytopathology against histopathology. The PPV of various IAC categories for diagnosing in situ or frank malignancy was computed to estimate the ROM of each category. A p value of <0.05 was taken as significant. All statistical analyses were performed in R v3.6.3 and SPSS v23.0.

A total of 1,147 breasts FNAB were examined in this study. A majority of these specimens were received from female patients (96.8%, median age: 34.5 years, interquartile range [IQR]: 23–45 years), with remainder of male patients (3.2%, median age: 45.0 years, interquartile range: 28–59 years). Breast lesions were equitably distributed with 45.2% arising in the right breast, 51.2% in the left, and 3.5% were bilateral. Precise quadrant-wise information was available in 59.6% of cases and their distribution is depicted in Figure 1. Of the total 1,147 cases, 442 (38.5%) underwent ROSE. Of the total 1,147 cases, 624 (54.4%) had histopathology follow-up.

Overall, the 1,147 cases were subclassified as 4.9% inadequate, 65.3% benign, 7.8% atypical, 3.3% suspicious for malignancy, and 18.7% malignant. The most common breast lesion under the benign category was fibroadenoma (309, 41.3%). Other entities included inflammatory lesions (47, 6.3%), granulomatous mastitis (26, 3.5%) (Fig. 2a, b), gynecomastia (23, 3.1%), galactocele (8, 1.1%) (Fig. 2c), and miscellaneous entities, like keratinous cyst, fat necrosis (Fig. 2d), and filariasis (Fig. 3a, b). The atypical category included lesions with atypical cells (44, 48.9%) and fibroepithelial lesions (e.g., fibroadenoma vs. low-grade phyllodes) (46, 51.1%). The suspicious for malignancy category included lesions suspicious for invasive carcinoma no special type (30, 79%) and suspicious for papillary carcinoma (9, 23.6%), and low-grade lymphoma (1, 2.6%). Ductal carcinoma was the most common lesion in the malignant category accounting for 203 (94.9%) cases followed by mucinous carcinoma (2, 0.9%) and malignant phyllodes tumor (1, 0.5%). The ROM was also assessed for the different categories and was found to be 16% for the inadequate, 0.7% for benign, 23.3% for atypical, 94.1% for suspicious for malignancy, and 100% for the malignant category.

In 705 (61.5%) cases where ROSE was not implemented the categories were as follows: inadequate (48, 6.8%), benign (443, 62.8%), atypical (53, 7.5%), suspicious for malignancy (31, 4.4%), and malignant (130, 18.4%). Of these cases without ROSE, histopathology follow-up was undertaken in 390 (55.3%) cases. Among these, 22 cases inadequate on cytopathology, were found on histopathology to be suspicious/malignant in 5 cases and benign (fibroadenoma, galactocele, lipoma, keratinous cyst, etc.) in the remaining 17 cases. A total of 173 benign cases (39.1%) had histopathology and only 3 cases showed a discrepancy in classification. Among the atypical, 44 (83.0%) underwent histopathology follow-up and were found to be indeterminate, in situ or malignant lesions. Of the suspicious of malignancy, 30 (96.8%) cases were followed up with histopathology and 28 (93.3%) of these revealed in situ or invasive malignancy. One case of suspected papillary carcinoma reported on cytopathology was later categorized to be indeterminate as the CNB was reported as a papillary neoplasm with atypia. Similarly, the malignant cytopathology group had histopathology follow-up in 121 (93.1%) cases, with malignancy confirmed in 98.3%, and in 2 cases (1.7%) the CNB yielded a nondiagnostic sample. The corresponding figures for samples that were subjected to ROSE are described in detail in the following paragraphs.

ROSE was carried out in 442 (38.5%) samples yielding a preliminary diagnosis of inadequate (8, 1.8%), benign (316, 71.5%), atypical (23, 5.2%), suspicious for malignancy (14, 3.2%), and malignant (81, 18.3%), respectively. These preliminary diagnostic categories were compared against those assigned by final cytopathology and histopathology (Fig. 4). The comparison of ROSE categories against the final cytopathology categories showed 96.2% concordance. ROSE categories were compared against the final categories assigned by histopathology (Fig. 4a, b). Benign and malignant conditions showed good levels of congruence with histopathology.

We further evaluated whether performing ROSE improved the final IAC results. For this, we compared the frequency with which various IAC categories were assigned to specimens which had undergone ROSE (442, 38.5%) versus those which had not undergone ROSE (705, 61.5%) (Table 1). The most significant impact of ROSE was seen in the reduction of inadequate (p < 0.001) and suspicious for malignancy (p = 0.010) categories. ROSE enabled better classification of benign lesions (p = 0.027) but showed little change in the frequency with which atypical and malignant specimens were categorized.

We evaluated the performance of breast cytopathology in our cases against histopathology. This was important to identify the areas that were lagging behind in our breast pathology services, and also to establish a reproducible system incorporating ROSE, the IAC Reporting System and histopathology to monitor and improve various components of our services in the future.

We first compared how well cytopathology categorized cases against broad histopathology categories (Fig. 5). We stratified this by including ROSE in the cytopathology workup (Fig. 5a–c). As is evident from the heatmaps, ROSE reduced the number of outliers’ diagnoses substantially and assigned benign and malignant categories more accurately. Samples that were subjected to ROSE showed only 1 benign, 6 atypical, and 1 suspicious of malignancy case that had to be reclassified on histopathology (Fig. 5a). The single benign case that had to be reclassified on histopathology showed fat necrosis on ROSE. It was subjected to CNB due to high clinical suspicion and was found to be a malignant lesion. FNAB most likely had sampled the fat necrosis surrounding the tumor. Six cases categorized as atypical by ROSE were fibroadenomas on histopathology. The young age of the patients and the marked stromal cellularity had flagged the mismatch, prompting us to confirm the diagnosis by histopathology. Three cases with benign, suspicious for malignancy, and malignant diagnoses on ROSE, could not be confirmed on histopathology due to nonrepresentative samples and lack of patient follow-up.

In contrast to the above analysis, specimens which did not undergo ROSE showed a larger number of recategorizations on histopathology. These included 5 inadequate, 4 benign, 16 atypical, 3 suspicious for malignancy, and 2 malignant cases which had to be recategorized (Fig. 5b). The 16 atypical cases showed lactational atypia (Fig. 6a, b), infarcted fibroadenoma, benign breast changes, and fat necrosis on histopathology. The 5 inadequate cases all were malignant, and underscore the importance of ROSE in assessing adequacy on-site minimizing missed and delayed diagnoses.

While the above analysis drew comparisons across broad categories of cytopathology and histopathology, we also wanted to assess how specific lesions had fared between the 2 techniques: how accurate was cytopathology (both with and without ROSE) in identifying the most common lesions (Fig. 5d). We found that a large majority of benign conditions were correctly classified by cytopathology, with 96.2% of fibroadenomas and 100% of acute and granulomatous mastitis identified accurately. Only 2.7% of fibroadenomas and 9.8% of benign breast lesions were labeled atypical on cytopathology. Half (50.0%) of the fibrocystic lesions and papillomas was classified as benign or atypical. Other less common benign entities included lipoma, fat necrosis, galactocele, filariasis, benign fibroepithelial polyps, gynecomastia, adenolipoma, and duct ectasia. These were largely (76.3%) identified correctly by cytopathology (Fig. 5d).

Among breast lesions with indeterminate histopathology, low-grade phyllodes tumor was the commonest and 32 (94.1%) of these were classified as atypical on cytopathology and 2 (5.9%) as benign fibroadenomas. The review of these 2 cases showed increased stromal cellularity, altered stromal-to-epithelial ratio and plump spindle cells in the background (Fig. 7a–d). Benign phyllodes tumor can be difficult to distinguish from fibroadenoma on cytopathology [10]. Other less common indeterminate entities included atypical or suspicious of malignancy lesions (Fig. 5d). Our cohort had very few cases of in situ carcinomas, and 3 (75.0%) of these were flagged as atypical, suspicious of malignancy, or malignant by cytopathology, with 1 high grade DCIS being misclassified as a benign lesion on cytopathology (Fig. 5d), which on review was due to inadequate sampling of a deep-seated lesion. Among invasive carcinomas, 187 (82.0%) were correctly categorized as malignant by cytopathology (Fig. 8a, b), while the remainder were categorized as atypical 12 (5.3%) or suspicious for malignancy 24 (10.5%). Other less common malignant lesions, like papillary carcinoma (Fig. 8c, d), lobular carcinoma, mucinous carcinoma, non-Hodgkin’s lymphoma (Fig. 9a, b), metaplastic carcinoma and malignant phyllodes tumor (Fig. 9c, d) were labeled as malignant (11, 50.0%), or suspicious for malignancy (7, 31.8%) with 4 (18.2%) being classified as atypical (Fig. 5d). The 16 atypical cases that had been typed as atypical on FNAB had revealed limited cytological features, which could be confirmed as malignant on histopathology (Fig. 5d).

The analysis of breast FNAB against histopathology excluding the cases excluded final inadequate and atypical cases (Table 2). We stratified this analysis by 2 scenarios. First, how well did cytopathology identify the cases that were eventually flagged in situ or malignant by histopathology, and how did incorporating ROSE affect this performance. FNAB picked up malignancies with an overall 86.1% sensitivity and 99.6% specificity, and excluded malignancies with a NPV of 89.9%. Importantly, all of these performance metrics were substantially improved by using ROSE (Table 2). Second, how well did the IAC categories of suspicious for malignancy and malignant identify in situ and malignant histopathology? As would be expected, by widening the net with both suspicious and malignant cases, the performance of FNAB went substantially up with 99.1% sensitivity and 99.3% specificity. Incorporating suspicious for malignancy cases in the comparison, the impact of ROSE was minimal (Table 2).

The performance of FNAB against histopathology was also analyzed with atypical cytology cases included (Table 3). We re-analyzed the above scenarios and found that cytopathology identified malignancies with an overall 80.5% sensitivity and 99.7% specificity, and NPV of 91.7%, and was substantially improved by ROSE (Table 3). When we expanded the definition and compared the performance of suspicious for malignancy and malignant cases in correctly identifying in situ and malignant histopathology, we noted a substantial increase in sensitivity (92.4%), specificity (99.4%), and NPV (94.6%). Cases subjected to ROSE again performed better on all metrics; however, the gain was smaller due to the inclusion of atypical and suspicious for malignancy cases in the analysis (Table 3).

A crucial goal of breast cytology and histopathology is to recognize malignancy in a timely and accurate fashion: the PPV of the IAC categories yielding a diagnosis of in situ or invasive carcinoma in histopathology was calculated and stratified by the application of ROSE (Table 4). There was a distinct rise in ROM across IAC categories from inadequate to malignant, and ROSE enhanced this gradient by minimizing potentially malignant cases in the inadequate (0%), benign (0.9%), and atypical (4.3%) IAC categories. In contrast, the specimens which did not undergo ROSE showed a significantly higher ROM in inadequate (18.2%) and atypical (34.9%) categories (p < 0.001).

A key metric in quality control is the false negative (FN) rate and is due to operator failure due to poor localization and poor FNAB technique of the sample or inability of the pathologist to detect subtle cytopathological features of malignancy. International guidelines recommend that FN rates should be <5% [2, 3]. Our pathology services performed well on this metric with a 0.71% (2/282) FN rate, with only 2 cases benign by ROSE and/or final cytopathology and malignant on histopathology (Fig. 5c). These 2 cases had revealed fat necrosis from deep-seated breast lumps. A high index of clinical-radiological suspicion ensured that we confirmed these cases with histopathology.

However, out of the total 749 cases that were categorized as benign on FNAB, only 285 were followed up with a CNB or excision biopsy based on their clinical-radiological suspicions. Of these 285 cases, 282 could be confirmed as benign on CNB, but 3 cases were indeterminate and lost to follow-up. In the remaining 464 cases the FNAB and clinical-radiological findings were unequivocally diagnostic of benign lesions and were not biopsied and not followed up for potential FN lesions and late development of malignancy in the same quadrant of the breast. Hence, the FN rate of 0.71% reported in this study represents only those benign lesions that underwent further histopathology examination. An equally important measure is the false positivity (FP) rate, representing over-diagnosis and mandate careful auditing. Ideally, FP rates should be <1% [2, 3], with our cases showing no malignant categorization on cytopathology to be benign on histopathology (Fig. 5c).

There are considerable variations in the literature regarding insufficient/inadequate rates, which can be due to the inexperience of FNAB operators, the varying mix of patients, use of mammographic screening and type of lesions (palpable or impalpable) vary from 0.7 to 47% [1, 7, 9]. We noted that 4.9% of the total 1,147 FNAB cases in this study were inadequate and less (1.8%) with ROSE (Fig. 4). Furthermore, 4.0% of FNAB that ultimately underwent histopathology had been deemed inadequate (Fig. 5c). We found 0.64% (4) cases with inadequate cytopathology to be malignant on histopathology, and 3.3% (38) were suspicious for malignancy out of the total 1,147 cases. Of the cases which had histopathology, 5.9% had been flagged as suspicious for malignancy (Fig. 5c). Of the specimens that underwent ROSE, 3.2% were suspicious for malignancy (Fig. 4) The ROM for atypical and suspicious of malignancy cases were 23.2% and 94.1%, respectively (Table 5), and are comparable to those previously reported [2].

Breast lumps are common in women of all ages and breast cancer is the leading cause of cancer in women worldwide. Breast cancer comprises 23% of cancer burden worldwide, with 2.1 million new cases and 6,27,000 deaths annually [11‒14]. FNAB and CNB, along with mammography and clinical evaluation, form crucial parts of the “triple test” for diagnosing breast lumps [9]. FNAB is sensitive and specific for diagnosing both benign and malignant breast lesions [9, 10]. It can also reliably pick up radiologically detectable nonpalpable lesions, and can achieve sensitivities of up to 90–95% [1, 8, 15‒17]. But FNAB has its limitations and CNB is required to confirm lesions, such as carcinoma in situ, calcifications, and proliferative tumors [18‒20]. However, CNB is not only more invasive but also remains prohibitively expensive and inaccessible in low-resource countries, like India [10, 21‒23]. FNAB and CNB can complement each other depending on the type of resources available at a health-care facility, the economic constraints, the nature of a lesion, the skill of the operator sampling the lesion, and the skill of the pathologist examining the specimens [24, 25].

The introduction of ROSE and the IAC Yokohama System for Reporting Breast FNAB Cytopathology have structured and significantly improved the utility of FNAB [1]. We studied the impact of these protocols in our breast FNAB reporting and observed distinct improvements. ROSE substantially improved the final diagnoses (Fig. 4) and reduced the discordance between cytopathology and histopathology (Fig. 5). ROSE significantly reduced inadequate sampling and the suspicious for malignancy category (Table 1). ROSE reduced the financial burden and inconvenience of patients from having to revisit. Overall, ROSE was significantly helpful in ruling out malignant lesions, but showed no significant improvement in ruling in malignancy (Table 1). This reflects the spectrum of breast cases which are predominantly benign with a smaller proportion of malignancies. It also reflects a tendency to err on the side of caution in our cytology reporting. Despite its better performance, a few cases did show a mismatch between ROSE and the final cytopathology and/or histopathology diagnosis. These were predominantly atypical and suspicious lesions, including 10 cases of low-grade/benign phyllodes tumor which required reassignment at final reporting. Another 6 cases suspicious for malignancy at ROSE were eventually found malignant by final cytopathology and histopathology.

Breast cytopathology at our center showed overall high sensitivity (86.1%) and specificity (99.6%) at diagnosing malignancies. Including ROSE in the workup, substantially enhanced the sensitivity (92.9%) and specificity (100%) of cytopathology (Table 2). Expanding the net by including both suspicious for malignancy and malignant cases raised the sensitivity (99.1%) of FNAB further, with a specificity of 99.3%. However, with the inclusion of suspicious for malignancy cases, ROSE contributed negligible improvement in picking up malignant cases. This indicates that ROSE helps weed out suspicious and ambiguous cases early in the workflow (Table 2).

The IAC Yokohama System also helps monitor the ROM in patients classified under different IAC categories, enabling the pathologist to better flag the cases that would need further histopathology confirmation, and also offer more robust recommendations to the treating surgeons [1]. We found the ROM increase along a gradient from inadequate to malignant IAC categories (Table 4). However, without ROSE, the ROM among inadequate cases jumped to 18.2%, while with ROSE it was zero. Furthermore, ROSE shifted the ROM gradient sharply toward the suspicious for malignancy and malignant end of the IAC spectrum, which otherwise spilled onto the atypical and inadequate categories without ROSE (Table 4). This underscores the advantage of combining ROSE and the IAC Yokohama System for monitoring and predicting the ROM.

The major performance metrics were FN rate (0.71%), FP rate (0.0%), inadequate rate (4.9%), and suspicious for malignancy rate (3.3%), and showed further improvements in each of these parameters with ROSE. FNAB is preferred to CNB partly because of financial and resource constraints. FNAB is less reliable in the small number of patients with deep-seated breast lumps surrounded by excessive fatty tissue, which are at risk of delayed and missed diagnoses, and after thorough clinical-radiological evaluation should be offered FNAB by an experienced operator under ultrasound-guidance or immediate CNB [26].

A majority of our patients, including those financially constrained, often travel several miles to access pathology services. Even the few cases that get diagnosed as inadequate or inconclusive, are missed opportunities because most of these patients fail to return for follow-up until much later when the disease has advanced and/or has become unmanageable. Such missed opportunities highlight the importance of ROSE, regular monitoring of IAC ROM rates, and early ultrasound-guided FNAB where CNB is unaffordable.

Moving forward, harnessing long-term follow-up data will be a goal at our center to bring out the true FN rates in our patients and further strengthen our services. Besides the above challenges that are unique to low-resource countries, we also noticed the need to improve supervision and training of less experienced pathologists. Low-grade phyllodes tumors are difficult to diagnose on cytopathology, and all suspect cases should be reviewed and confirmed by an experienced pathologist [10, 27]. Such measures along with inclusion of ROSE can prevent delayed and missed diagnoses.

If a malignant FNAB diagnosis is in accordance with clinical-radiological findings in the triple test, and material is available in the cell block for prognostic markers, neoadjuvant chemotherapy and surgery can be commenced [3, 28]. If the FNAB diagnosis does not correlate with the clinical and imaging findings, then CNB or simple excision becomes mandatory [2, 23]. When lymph nodes are palpable or suspicious on ultrasound, FNAB is recommended to stage the patient [2, 29, 30].

We compared our findings with other studies and found largely similar and a few divergent trends (Table 5). Several studies have reported similar rates of inadequate samples (1.4–5.7%) as reported in our study (overall 4.9%; 1.8% with ROSE) (Table 5) [4, 7, 15, 17, 31‒33]. However, a few studies had recorded much higher rates of inadequate samples (11.0–15.5%) [9, 34, 35]. The IAC Reporting System recommends that operators should aim for an inadequate sample rate of <5.0%, which should be even lower if ROSE is implemented [3, 7, 9, 35, 36]. The proportion of benign cases (65.3%) in our cohort was also similar to that observed in various studies (41.8–82.6%) (Table 5) [3, 7, 9, 11, 13, 37]. Among benign cases, fibroadenomas comprised 58.1% of total cases, which was similar to that noted by previous studies, 48.8–67.7% [38‒40]. Follow-up histopathology was not required for most benign cases, especially if the patient was negative on clinical-radiological evaluation for >6–12 months [3, 41]. The proportion of atypical (7.8%) and suspicious (3.3%) cases in our study were similar to that observed in other studies [4, 7, 9, 15, 17, 37], except a few studies where such cases were recorded in higher proportions, 10.4–13.7% atypical cases and 9.3–11.0% suspicious for malignancy cases [4, 34, 42, 43]. The proportion of malignant lesions varied across studies, possibly reflecting the type of patients being cared for by the respective centers (Table 5). The overall performance of cytopathology in accurately diagnosing in situ and malignant breast lesions in our study was similar [4, 9, 15, 17] to better [7, 37] than that observed in contemporary studies (Table 5).

Our study shows that incorporating the IAC Yokohama System for Reporting Breast FNAB Cytopathology with ROSE can improve early and accurate diagnosis of breast lesions, prevent missed diagnoses, and provide reliable estimates of ROM in a given patient population. This is especially important for low- and middle-income countries where CNB is an expensive option. Our results also demonstrate that these protocols can help create a standardized and reproducible system for monitoring and auditing of breast pathology services, which can help identify the areas that need strengthening and improve the training being delivered at pathology centers.

Written informed consent was taken from all patients for the procedure of fine-needle aspiration biopsy. The retrospective analysis was undertaken after approval from the Institutional Ethics Committee on human research (EC/OA -150/2019).

The authors declare no conflicts of interest.

This study received no funding from any source.

N.A. and K.K. conceptualized and designed the study, performed literature search, and carried out the clinical study. S.T. carried out data collection, clinical study, preliminary data analysis, and wrote the manuscript. P.S. carried out formal data analysis, visualization, study design, and wrote the manuscript. M.A. and V.S. assisted in study design and literature search. All the authors contributed to the final review and editing of the manuscript.

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