FNAC Versus CNB: Who Wins the Match in Breast Lesions?

The triple test lies at the heart of preoperative diagnosis of breast lesions. Raised awareness and self-assessment have significantly increased the rate of detection of breast pathologies. The managing clinicians usually decide the imaging and pathological modalities to the best interest of the patients. Core needle biopsy (CNB), cell-block studies, and fine needle aspiration cytology (FNAC) coupled with rapid on-site evaluation (ROSE) have significantly increased the accuracy of preoperative diagnosis. Immunocytochemistry, immunohistochemistry on cell blocks, and other ancillary studies give confidence to the clinicians to decide the best treatment strategies.

Breast swellings are one of the most common pathologies encountered in a pathology clinic. The lesions range from cysts to malignant tumors. The increased awareness to breast cancers has led to increase in self-detected swellings as well as apprehension on the part of the patients. Cold statistics show that breast cancer is the second most common cancer in the world and the most frequent cancer among women with an estimated 1.67 million new cancer cases diagnosed in 2012.[1]

TRIPLE TEST

The recommended approach to breast lesions is the age-old triple assessment or triple test. This includes a) a detailed history (including family history) and a thorough clinical examination, b) imaging (mammography and/or ultrasound), and c) preoperative cytodiagnosis (fine needle aspiration cytology or FNAC). Core needle biopsy (CNB) has proven its utility and sometimes scores over FNAC and has been added as an important modality in preoperative diagnosis alongside FNAC. The triple test is considered positive if any of the three parameters is positive and negative if all three are negative.[2] The triple test has a sensitivity (true positive rate) of 99.6%, and a specificity of 93%.[3]

The role of history taking cannot be overemphasized. A detailed history can help in diagnosis of various benign and malignant breast diseases. Reproductive history and lifestyle including lactational history, exposure to endogenous and exogenous hormones, and a family history of breast or related cancers are of paramount importance. History of duration, progression, pain, other associated swellings, relation with menses, nipple discharges, etc., are routinely inquired for.

IMAGING

Imaging of breast lesions is very helpful in diagnosis and triaging. For women <40 years, ultrasound alone is the investigation of choice whereas mammography is recommended for imaging of women >40 years. However, mammography is indicated in women <40 years with proven breast cancer. It must be remembered that about 5–15% of palpable cancers may be missed on mammogram, majority of which can be picked up by targeted ultrasound.[4] Magnetic resonance imaging (MRI) is the most sensitive method and is particularly useful in screening individuals of very high risk (e.g., carriers of mutated BRCA 1 and 2 genes), pretreatment staging and routinely for invasive lobular carcinoma.[4]

CLINICAL EXAMINATION

Thorough clinical examination is the key to diagnosis and also a guide to the selection of pretreatment diagnostic modality. The examination of the other breast and both the axillae are routinely undertaken. Size and location of the lesion, overlying skin changes, status of nipple, fixity to skin, and other structures are always evaluated.

ROLE OF FINE NEEDLE ASPIRATION CYTOLOGY

FNAC, with or without image guidance, has been a pathologist's boon as it can provide very rapid and fairly accurate diagnosis of breast lesions to the anxious patient and the treating clinician. The sensitivity and specificity of FNAC varies from 77–97% and 92–99%, respectively, as per various studies.[5] Stereotactic FNAC has further bettered the sensitivity and specificity of impalpable breast lesions. Being an inexpensive, minimally invasive procedure with negligible and rare complication rate, it has received wide acceptance of patients. The pathologist also feels confident as multiple passes can be taken from multiple sites of the breast as well as axillary or other lymph nodes in the same sitting. The aspirates can now be used for all types of immunocytochemistry and ancillary techniques just like the tissue sections. However, there is a need of an experienced cytopathologist for diagnosis the wide spectrum of breast lesions. Again, lack of adequate aspirate is another drawback which can add to the agony of the patient and the doctor alike. Similarly, certain sclerosing lesions like sclerosing adenosis, radial scar, sclerosing fibroadenoma, infiltrating lobular carcinoma can result in poor cellular yield. As cytological smears cannot reliably predict invasion, benign and borderline lesions cannot always be reliably distinguished from their malignant counterparts. Distinguishing atypical ductal hyperplasia (ADH) from ductal carcinoma in situ (DCIS) and an invasive ductal carcinoma can be painstaking to the most experienced pathologists. Papillary lesions remain another nightmare for cytopathologists where it encompass a wide variety of lesions including intraductal papillomas, intraductal papillary carcinoma, encapsulated papillary carcinoma, solid papillary carcinoma, invasive papillary carcinoma, and the invasive micropapillary carcinoma. To even complicate the issue, the intraductal papillomas can have components of ADH or DCIS. Diagnosing low-grade malignancies like tubular carcinomas and lobular carcinomas as well picking up the mixed types are some other drawbacks which this hugely popular method suffers from.

Reporting of many of the prognostic parameters (mitosis, lymphovascular emboli, perineural invasion, percentage of the DCIS component) are also virtually impossible from smear cytology.

However, some of the inherent problems of FNAC can be solved. First of all, there should be judicious selection of cases. The image guidance is to be taken whenever found necessary. Multiple passes and multiple excursions per pass will help improve the yield and provide additional material for preparation of cell blocks. The rapid on-site evaluation (ROSE) will significantly improve the overall aspirate as it will guide proper specimen adequacy and triaging of samples. A rapid Romanowsky stain like Diff-Quick or toluidine blue or a rapid Papanicolaou can be used for onsite evaluation.

CORE NEEDLE BIOPSY

CNB has been the relatively new kid in the block which has become increasingly popular particularly with some of the surgeons. The sensitivity, specificity, positive, and negative predictive values are comparable with FNAC with some studies showing better performance but others do not. However, the specificity remains somewhat better in most of the studies.[6789] The use of stereotactic-guided vacuum assisted core needle biopsy (VACB) further increases the sensitivity. The 14G needles are most commonly used whereas some centers practicing VACB use 11G needles. Three to six cores are often obtained for adequate evaluation. The better assessment of architecture of the tissue provides the advantage of diagnosing many gray areas. It can distinguish between ADH, DCIS, and invasive malignancies, though not always. Similarly, diagnosing sclerosing lesions, papillary lesions, mixed carcinomas, distinguishing malignant phyllodes tumor from their benign, and borderline counterparts become easier than from the aspirates but is far from being full proof. But the reporting of prognostic parameters (already mentioned), the performance of immunohistochemistry as well as availability of more tissue for FISH and other ancillary techniques remain as significant benefits. However, the procedure is expensive, requires the infrastructure for imaging, a radiologist, and the need for local anesthesia. Added to this there is the problem of increased turn-around-time (TAT), infrastructure for tissue processing, and somewhat higher rate of complication (pain, hematoma, needle tract implantation, and rarely pneumothorax). The procedure may again be not suitable for cystic and mucinous lesions or patients on anticoagulant therapy. The problem with TAT can partly be resolved by taking imprint of cores but there lie the drawbacks of architectural distortions and specimen dry out.

PRACTICAL COMBINATORIAL APPROACH

It must be understood that there is no single guideline to which pathological test is to be used for preoperative diagnosis. Both FNAC and CNB are important diagnostic modalities and they are complimentary to each other. They can even be combined together for obtaining the maximum preoperative information that can benefit the patient and solve the dilemma of the treating clinician to decide the best treatment approach. The approach should always be to start with the triple test. If the clinical and radiological assessment indicate a benign or a cystic lesion, it is better to go for FNAC. For nonpalpable lesions and those with microcalcifications, it is better to opt for CNB. ROSE should be done for all FNAC cases and efforts to obtain adequate material for cell blocks by multiple passes is recommended. Cases of FNAC where there is inadequate material or atypical cells on ROSE should be subjected to FNAC as are those cases where the BI-RADS score is high or discrepant with the cytology findings.[5]

All said and done, both FNAC and CNB being operator and interpreter dependent procedures, the need for proper training, quality control, and vast experience are of paramount importance.

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Conflicts of interest

There are no conflicts of interest.