Breast lesions represent one of the most common clinical presentations encountered in surgical and radiological practice, and their accurate diagnosis is of paramount importance for guiding appropriate management. The spectrum of palpable breast lesions ranges from benign conditions such as fibroadenoma, fibrocystic disease, and inflammatory lesions to malignant tumors like invasive ductal carcinoma and lobular carcinoma. Breast cancer remains the most prevalent malignancy among women worldwide and a leading cause of cancer-related mortality. According to global cancer statistics, it accounts for nearly 24% of all female cancers, emphasizing the need for early and precise diagnostic tools to differentiate benign from malignant pathology [1]. Among the available diagnostic modalities, cytological and histopathological methods have established themselves as key components of the triple assessment of breast lumps-clinical examination, imaging, and tissue diagnosis. Fine Needle Aspiration Cytology (FNAC) has traditionally been the first-line diagnostic technique owing to its simplicity, cost-effectiveness, rapid turnaround time, and minimal invasiveness. FNAC provides cytological details that help categorize lesions into benign, suspicious, or malignant groups, aiding clinicians in determining the next steps in management. The diagnostic accuracy of FNAC, however, is influenced by several factors including the skill of the operator, the adequacy of aspirated material, and the cytopathologist’s interpretative expertise [2]. Core Needle Biopsy (CNB), on the other hand, has gained increasing prominence over the past two decades as an alternative or complementary method. CNB provides a histological specimen with preserved tissue architecture, allowing for evaluation of invasiveness, receptor status (ER, PR, HER2), and tumor grading-parameters critical for treatment planning. Moreover, CNB reduces the need for diagnostic open biopsies and has been shown to improve preoperative diagnosis rates. While FNAC yields cytological smears, CNB offers histological sections that allow a definitive differentiation between in situ and invasive carcinomas, as well as accurate subtyping of tumors[3]. The comparative diagnostic accuracy between FNAC and CNB has been an ongoing subject of debate. FNAC is highly accurate in diagnosing obvious benign and malignant lesions but demonstrates limitations in distinguishing atypical or borderline lesions such as ductal carcinoma in situ (DCIS), lobular carcinoma, and fibroepithelial tumors with stromal overgrowth. CNB, by contrast, has demonstrated superior diagnostic yield in such indeterminate cases but is more invasive, costlier, and requires local anesthesia and imaging guidance in certain cases. Studies have shown FNAC to have sensitivity ranging between 80-95% and specificity of 90-100%, while CNB often exceeds 95% sensitivity and specificity [4]. Despite the apparent advantages of CNB, FNAC remains widely utilized in low-resource and high-volume clinical settings because of its rapid results and minimal morbidity. The World Health Organization (WHO) continues to recognize FNAC as a valuable diagnostic tool in breast lesion evaluation, particularly when performed in conjunction with clinical and radiologic findings. However, the ultimate diagnostic gold standard remains histopathological examination of excised tissue, against which both FNAC and CNB are compared for accuracy determination.[5] Aim To compare the diagnostic accuracy of Fine Needle Aspiration Cytology (FNAC) and Core Needle Biopsy (CNB) in palpable breast lesions using histopathology as the gold standard. Objectives 1. To determine the sensitivity, specificity, and diagnostic accuracy of FNAC in palpable breast lesions compared with histopathology. 2. To evaluate the diagnostic performance of Core Needle Biopsy (CNB) in palpable breast lesions using histopathological findings as reference. 3. To compare and analyze the concordance between FNAC, CNB, and final histopathological diagnosis.

Source of Data The study data were obtained from patients presenting with palpable breast lumps attending the Department of Surgery and Pathology at a tertiary care teaching hospital. All patients who underwent FNAC, core needle biopsy, and subsequent excision biopsy or mastectomy were included. Study Design A prospective comparative observational study. Study Location The study was conducted in the Department of Pathology and Surgery at a tertiary care hospital equipped with histopathology and cytopathology units. Study Duration The study was carried out over a period of 18 months, from January 2023 to June 2024. Sample Size A total of 200 patients with palpable breast lesions were included in the study. Inclusion Criteria • Female patients aged 18 years and above presenting with palpable breast lumps. • Patients who underwent both FNAC and Core Needle Biopsy followed by surgical excision or mastectomy. • Patients who gave informed written consent. Exclusion Criteria • Patients with non-palpable lesions detected only on imaging. • Patients who had undergone prior chemotherapy or radiotherapy. • Inadequate or unsatisfactory cytology/biopsy samples. • Recurrent breast malignancies or previously treated cases. Procedure and Methodology After detailed clinical examination and imaging (mammography or ultrasonography), each patient underwent both FNAC and CNB of the palpable lesion. • FNAC: Performed using a 22-23 gauge needle attached to a 10 mL syringe under aseptic precautions. Multiple passes were made, and smears were prepared immediately on clean glass slides. Air-dried and alcohol-fixed smears were stained using May-Grünwald-Giemsa (MGG) and Papanicolaou stains. • CNB: Performed using an 18-gauge automated spring-loaded biopsy gun under local anesthesia. Two to three cores were obtained from representative areas of the lump. The tissue cores were immediately fixed in 10% neutral buffered formalin. • Histopathology: All patients subsequently underwent surgical excision (lumpectomy or mastectomy). Histopathological examination of the excised specimen was considered the gold standard for diagnosis. Sample Processing Cytology smears were evaluated and categorized according to the National Cancer Institute (NCI) guidelines for reporting breast FNAC results. Core biopsy and histopathology specimens were processed through routine paraffin embedding and stained with hematoxylin and eosin (H&E). Immunohistochemistry (IHC) was performed when necessary for confirmation or subtyping. Statistical Methods Data were entered in Microsoft Excel and analyzed using SPSS version 26. Diagnostic indices such as sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall diagnostic accuracy were calculated for both FNAC and CNB using histopathology as the gold standard. Concordance between FNAC, CNB, and histopathology was analyzed using Cohen’s Kappa coefficient. A p-value <0.05 was considered statistically significant. Data Collection All relevant clinical, radiological, cytological, and histopathological findings were systematically recorded in a structured proforma. Each case was cross-verified with final histopathological diagnosis to assess the diagnostic accuracy of FNAC and CNB.

Table 1: Head-to-head comparison of diagnostic accuracy (FNAC vs CNB) against histopathology (N = 200) Metric FNAC CNB Between-test comparison Reference prevalence (HPE malignant) 91 / 200 (45.5%) 91 / 200 (45.5%) - TP / FN / FP / TN 80 / 11 / 7 / 102 86 / 5 / 4 / 105 - Sensitivity 87.9% (80/91) [79.6-93.1] 94.5% (86/91) [87.8-97.6] McNemar among malignant: b=7, c=1 → p = 0.070 Specificity 93.6% (102/109) [87.3-96.9] 96.3% (105/109) [90.9-98.6] McNemar among benign: b=5, c=2 → p = 0.453 PPV 92.0% (80/87) [84.3-96.0] 95.6% (86/90) [89.1-98.3] - NPV 90.3% (102/113) [83.4-94.5] 95.5% (105/110) [89.8-98.0] - Overall accuracy 91.0% (182/200) [86.2-94.2] 95.5% (191/200) [91.7-97.6] McNemar overall (paired): b=12, c=3 → p = 0.035 Notes: TP=True Positive; FN=False Negative; FP=False Positive; TN=True Negative. CIs are Wilson 95%. PPV/NPV are conditional on this cohort’s prevalence. Table 1 demonstrates that the overall prevalence of malignancy confirmed on histopathology was 45.5% (91/200). FNAC correctly identified 80 true positives and 102 true negatives, with 11 false negatives and 7 false positives, yielding a sensitivity of 87.9% (95% CI: 79.6-93.1) and specificity of 93.6% (95% CI: 87.3-96.9). The corresponding PPV and NPV were 92.0% and 90.3%, respectively, with an overall diagnostic accuracy of 91.0% (95% CI: 86.2-94.2). In contrast, CNB achieved 86 true positives and 105 true negatives, with fewer diagnostic errors-only 5 false negatives and 4 false positives. This translated into superior diagnostic indices: sensitivity 94.5% (95% CI: 87.8-97.6), specificity 96.3% (95% CI: 90.9-98.6), PPV 95.6%, and NPV 95.5%. The overall accuracy of CNB (95.5%) exceeded that of FNAC by 4.5 percentage points. Paired comparisons using McNemar’s test showed that the improvement in CNB accuracy was statistically significant (b = 12, c = 3; p = 0.035). Differences in sensitivity (p = 0.070) and specificity (p = 0.453) did not reach statistical significance individually, but the cumulative performance favored CNB. Table 2: FNAC versus histopathology (diagnostic performance and test of significance, N = 200) FNAC vs HPE (2×2) HPE Malignant HPE Benign Row total FNAC Positive 80 (TP) 7 (FP) 87 FNAC Negative 11 (FN) 102 (TN) 113 Column total 91 109 200 Diagnostic index (FNAC) Value (n/N) 95% CI Sensitivity 87.9% (80/91) 79.6-93.1 Specificity 93.6% (102/109) 87.3-96.9 PPV 92.0% (80/87) 84.3-96.0 NPV 90.3% (102/113) 83.4-94.5 Accuracy 91.0% (182/200) 86.2-94.2 Chi-square (association FNAC vs HPE): χ²=134.00, p < 0.001 Table 2 provides the detailed cross-tabulation and diagnostic indices for FNAC relative to the histopathological gold standard. Out of 91 malignant lesions, FNAC detected 80 true positives but missed 11 cases, while among 109 benign lesions, only 7 false positives were reported. Consequently, FNAC achieved a sensitivity of 87.9% (95% CI: 79.6-93.1), indicating good detection capability for malignant cases. The specificity of 93.6% (95% CI: 87.3-96.9) reflects a low false-positive rate. The PPV 92.0% (95% CI: 84.3-96.0) and NPV 90.3% (95% CI: 83.4-94.5) denote strong predictive validity in both directions. The overall accuracy was 91.0% (95% CI: 86.2-94.2). The strength of association between FNAC results and histopathology was highly significant (χ² = 134.00, p < 0.001), confirming FNAC as a dependable initial diagnostic tool for palpable breast lumps. Table 3: CNB versus histopathology (diagnostic performance and test of significance, N = 200) CNB vs HPE (2×2) HPE Malignant HPE Benign Row total CNB Positive 86 (TP) 4 (FP) 90 CNB Negative 5 (FN) 105 (TN) 110 Column total 91 109 200 Diagnostic index (CNB) Value (n/N) 95% CI Sensitivity 94.5% (86/91) 87.8-97.6 Specificity 96.3% (105/109) 90.9-98.6 PPV 95.6% (86/90) 89.1-98.3 NPV 95.5% (105/110) 89.8-98.0 Accuracy 95.5% (191/200) 91.7-97.6 CI method: Wilson 95%. Chi-square (association CNB vs HPE): χ²=165.34, p < 0.001 Table 3 summarizes the performance of CNB against histopathology. CNB correctly identified 86 malignant and 105 benign lesions, misclassifying only 9 cases in total (5 false negatives, 4 false positives). The resulting sensitivity (94.5%; 95% CI: 87.8-97.6) and specificity (96.3%; 95% CI: 90.9-98.6) are both superior to those of FNAC. Predictive values were similarly high, with PPV 95.6% (95% CI: 89.1-98.3) and NPV 95.5% (95% CI: 89.8-98.0). The overall accuracy reached 95.5% (95% CI: 91.7-97.6), and the association between CNB findings and histopathology was statistically significant (χ² = 165.34, p < 0.001). Table 4: Concordance and agreement among FNAC, CNB, and histopathology (N = 200) A. Pairwise agreement with HPE Pair Agreement, % (n/N) Cohen’s κ (95% CI) Significance FNAC vs HPE 91.0% (182/200) 0.818 [0.738-0.898] z-test vs κ=0: p < 0.001 CNB vs HPE 95.5% (191/200) 0.909 [0.851-0.967] z-test vs κ=0: p < 0.001 B. FNAC vs CNB (regardless of HPE) FNAC vs CNB (2×2) CNB Positive CNB Negative Row total FNAC Positive 81 (both +) 6 87 FNAC Negative 9 104 (both -) 113 Column total 90 110 200 Pairwise metric Value 95% CI Test of significance Overall agreement 92.5% (185/200) - - Cohen’s κ 0.848 [0.774-0.922] z-test vs κ=0: p < 0.001 McNemar (discordant) b=12 (FNAC wrong/CNB right), c=3 (CNB wrong/FNAC right) - p = 0.035 Table 4 presents measures of diagnostic agreement and concordance between FNAC, CNB, and histopathology. Pairwise comparison with histopathology revealed substantial agreement for FNAC (κ = 0.818; 95% CI: 0.738-0.898) and almost perfect agreement for CNB (κ = 0.909; 95% CI: 0.851-0.967), both statistically significant (p < 0.001). This indicates that while FNAC results closely match the final histopathological diagnosis, CNB achieves even higher concordance. When FNAC and CNB were compared directly, overall agreement was 92.5% (185/200) with Cohen’s κ = 0.848 (95% CI: 0.774-0.922), reflecting strong inter-method consistency. However, McNemar’s test (b = 12, c = 3; p = 0.035) identified a small but statistically significant discordance, with CNB outperforming FNAC in 12 instances where FNAC produced inaccurate results. Sensitivity-specificity component tests further revealed that CNB corrected seven malignant and five benign cases misclassified by FNAC, demonstrating its higher accuracy particularly in indeterminate or borderline lesions.

Across 200 palpable breast lesions with an HPE‐confirmed malignancy prevalence of 45.5%, head-to-head analysis shows that both tests perform strongly, but CNB edges out FNAC on every diagnostic metric. FNAC achieved Se 87.9% and Sp 93.6%, yielding PPV 92.0%, NPV 90.3%, and accuracy 91.0%. CNB improved these to Se 94.5%, Sp 96.3%, PPV 95.6%, NPV 95.5%, and accuracy 95.5%. The paired nature of data is important: although the sensitivity and specificity differences did not reach individual significance (McNemar malignant p=0.070, benign p=0.453), the overall paired McNemar test was significant (p=0.035), indicating that, case-for-case, CNB corrected more FNAC errors than vice-versa (b=12 vs c=3). The agreement statistics mirror this: κ=0.818 (FNAC vs HPE; substantial) and κ=0.909 (CNB vs HPE; almost perfect), with FNAC vs CNB κ=0.848, underscoring high, but not interchangeable, concordance. Dhaketa SS et al.(2025)[6] These findings sit squarely within published ranges. Multiple series and reviews describe FNAC sensitivity typically 80-95% with specificity 90-100%, shaped by operator technique, smear adequacy, and interpretive expertise de Cursi JA et al.(2020)[7]. FNAC performance (Se 88%, Sp 94%) is consistent with the upper-middle of that spectrum and reflects a low false-positive rate (7/109 benign) but the expected false-negative tail (11/91 malignant)-a pattern often attributed to low-grade carcinomas, lobular histology, DCIS without overt cytologic atypia, and fibroepithelial lesions with stromal overgrowth where architectural cues are decisive Sharif A et al.(2025)[8]. By contrast, CNB’s preservation of tissue architecture allows reliable invasion assessment, histologic subtyping, and-crucially for contemporary care-receptor testing; consequently, many cohorts report CNB sensitivity and specificity exceeding 90-95%, with fewer indeterminate or “suspicious” calls than FNAC Tripathi K et al.(2022)[9]. CNB figures (Se 94.5%, Sp 96.3%) align with this mature evidence base. The paired discordance pattern in data is instructive. Among malignant cases, CNB rescued seven instances miscalled by FNAC (b=7) and was itself rescued once by FNAC (c=1). This is the classic scenario in which CNB improves under-calling in lesions that depend on stromal-epithelial relationships or subtle invasion-situations where cytology alone can be equivocal Siddique R et al.(2022)[10]. On the benign side, CNB also reduced spurious positives (b=5 vs c=2), likely reflecting its clearer discrimination of papillary, sclerosing, or proliferative processes that may appear atypical cytologically but prove benign histologically Noor BA et al.(2022)[11]. The net effect-a statistically significant overall McNemar test-supports routine escalation to CNB when FNAC is inadequate, atypical, or discordant with clinical-radiologic impressions, a strategy recommended in many institutional algorithms Fimate P. (2020)[12]. predictive values also make epidemiologic sense given the cohort’s moderate malignancy prevalence (46%). PPV and NPV are prevalence-dependent; at this mid-range, both PPV and NPV remain high for each test, but CNB’s tighter CIs (e.g., NPV 95.5% with CI 89.8-98.0%) translate to narrower decision uncertainty at the patient level. The accuracy gap (4.5 percentage points) is clinically meaningful in preoperative planning, particularly where upfront systemic therapy or breast-conserving strategies hinge on a definitive invasive diagnosis and biomarkers Ali MT et al.(2024)[13]. Agreement metrics strengthen the message. Cohen’s κ values in series (0.82 for FNAC; 0.91 for CNB) map closely to prior reports that classify FNAC-HPE concordance as substantial and CNB-HPE as almost perfect Kim A et al.(2025)[14]. High FNAC-CNB agreement (92.5%; κ=0.85) is expected in clear-cut lesions, yet the asymmetric discordance shows why CNB is preferred when triple-test discordance arises or when definitive grading/ER-PR-HER2 is required Ahmed I et al.(2024)[15]. In short: FNAC remains an excellent first-line, rapid, low-cost triage tool, especially in high-volume or resource-constrained settings; CNB provides the confirmatory, architecture-preserving diagnosis that reduces false negatives and supports comprehensive treatment planning. Finally, chi-square associations (FNAC: χ²=134.00; CNB: χ²=165.34; both p<0.001) reiterate strong test-truth coupling, but the paired analysis is the right method to declare superiority, which have done. Together, these data support a pragmatic algorithm: start with FNAC for accessible palpable masses; proceed to CNB for inadequate/equivocal cytology or where histologic architecture and biomarkers will alter management; and prioritize CNB upfront in lesions with radiologic-clinical suspicion for DCIS, ILC, or complex fibroepithelial tumors Pyo JS et al.(2020)[16].

The present study comparing Fine Needle Aspiration Cytology (FNAC) and Core Needle Biopsy (CNB) in palpable breast lesions, with histopathology as the gold standard, demonstrates that both modalities are highly reliable for preoperative diagnosis, but CNB provides superior diagnostic accuracy. FNAC achieved a sensitivity of 87.9%, specificity of 93.6%, and overall accuracy of 91.0%, while CNB showed higher values-sensitivity 94.5%, specificity 96.3%, and accuracy 95.5%. The difference in diagnostic yield between the two techniques was statistically significant (McNemar p = 0.035), underscoring CNB’s advantage in reducing false negatives and providing more definitive tissue characterization. Cohen’s κ statistics further confirmed strong agreement of both methods with histopathology (FNAC κ = 0.818; CNB κ = 0.909), with CNB achieving near-perfect concordance. FNAC remains a valuable first-line investigation in resource-limited or high-volume centers due to its simplicity, low cost, and rapid results. However, CNB offers the additional advantage of preserving tissue architecture, facilitating histologic grading, and enabling receptor analysis, making it indispensable for comprehensive management planning. Hence, CNB should be preferred in cases where FNAC results are inadequate, equivocal, or discordant with clinical and imaging findings.

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