Nonoperative diagnostic procedures such as needle core biopsy or fine needle aspiration cytology (FNAC) are essential for appropriate decision-making in the management of the patient with benign or malignant breast disease. A conclusive radiological and histological diagnosis of benign breast disease allays anxiety in the woman concerned, especially if this can be achieved without surgical operation. Inadequate sampling from fibrotic lesions, such as lobular carcinoma, hyalinised fibroadenomas and scattered microcalcification, now limits the use of FNAC, which was once a popular diagnostic modality. Consequently more and more units are using stereotactic needle core biopsies in combination or as an adjunct to FNAC as a diagnostic tool. Needle core biopsies benefit from a higher sensitivity and specificity than FNAC (Britton 1999). More sections can be cut, and immunocytochemistry stains carried out on a needle core biopsy which may assist in reaching a diagnosis in equivocal cases. Needle core biopsies are also preferred to localised excision biopsies as they potentially spare patients with benign lesions from unnecessary surgery.

Frozen section examination is not recommended in screen-detected lesions because of the risk of a false-positive diagnosis with lesions such as radial scars and sclerosing adenosis (Nielsen 1987). If one is faced with an equivocal FNAC or needle core biopsy diagnosis, it is preferable to perform an excisional biopsy and confirm the diagnosis on the paraffin-embedded tissue rather than risk a misdiagnosis on frozen section. Screen-detected lesions are usually small, and it is preferable to assess the whole lesion after appropriate fixation. Partly sampling the lesion for frozen section may distort the specimen, which could interfere with the final diagnosis. Even with a palpable lump, there is no justification for using frozen section for primary diagnosis.

Meaningful cytology results, especially in impalpable lesions, depend on the experience of the aspirator (usually the radiologist), the quality of the prepared slides (radiologist, pathologist or laboratory biomedical scientist), the quality of the staining (laboratory biomedical scientist) and the experience of the reporting pathologist or cytopathologist. The experience of the cytopathologist is enhanced by the volume of different cases reported in each unit, complimented by multidisciplinary team discussion of these cases. The UK National Health Service Breast Screening Programme (NHSBSP 1993) devised a standardised format for reporting cytology similar to the radiological criteria. The criteria were updated in NHBSP Publication 50 (2001) which provides guidelines on nonoperative diagnostic procedures and reporting. The European Society of Mastology (EUSOMA) also applies similar reporting criteria (Perry et al. 2001).

Needle core biopsies can be sampled under ultrasound or stereotactic guidance. Larger and high-volume needle core biopsies can be obtained by a vacuum-assisted device (mammotome). If the target abnormality is mammographic calcification, the needle core biopsies can be placed in a small cassette and X-rayed to confirm the presence of calcification. The cassette will then be submitted to the laboratory for processing.

At least three levels should be examined histologically to obtain an adequate diagnosis on needle core biopsies. The greater the number of needle core biopsies, the easier it is for the pathologist to make a diagnosis. Brenner et al. (1996) reported increased diagnostic accuracy with increasing number of needle core biopsies. With five biopsies, diagnostic accuracy was 98 % for masses, 91 % for calcifications, 100 % for masses with calcification, 100 % for focal asymmetries and 86 % for architectural distortions. Bagnall et al. (2000) reached a similar conclusion when they assessed 57 consecutive stereotactic needle core biopsies. The authors reported that the presence of calcification in the specimen X-ray was associated with a high sensitivity. The presence of five or more flecks in three or more needle core biopsies gave an absolute sensitivity of 100 % for carcinoma. The use of a vacuum-assisted device also reduces the rate of false-negative biopsies (Burbank 1997). If microcalcification is being sought, further levels should be examined before rendering an inadequate specimen. The pathologist should also be aware of calcium oxalate (weddellite) which can be present in the specimen X-ray but absent in the tissue unless examined under polarising light. Renshaw (2001) found out that at least five sections of the needle core biopsy are required in order to identify atypical small acinar proliferations or ADH.

The UK NHSBSP (2001) devised criteria for reporting needle core biopsies, which were later adopted by EUSOMA (Perry 2001). Although the needle core biopsy reporting categories are similar to those of radiological and cytological reports, the B3 category does not strictly follow the same criteria applied to radiology and cytology features (NHSBSP 2001).

B1 is applied to a needle core biopsy that contains normal breast tissue or adipose tissue. The presence of normal breast tissue in needle core biopsies should not be reported as benign in the presence of a radiological lesion, unless this has been discussed at a multidisciplinary team meeting. Lipomas or hamartomas can give a B1 report; therefore, the clinical and radiological features should be taken into account when these lesions are suspected. Involuting lobules may contain microcalcification on histology, which was not apparent mammographically or on specimen X-rays. This microcalcification may not be representative of the radiological lesion, and a B1 report may be appropriate following multidisciplinary team discussion.

B2 confirms benignity in breast lesions such as fibroadenoma, fibrocystic change, sclerosing adenosis (Fig. 5.3) or fibrosis, with radiological evidence that the pathological lesion was sampled. Depending on the radiological features, the patient may return to routine screening.