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This category indicates an adequate sample showing cells characteristic of carcinoma, or other malignancy. Malignancy should never be diagnosed on the basis of a single criterion. Combinations of the features listed in the following table will be always necessary to achieve the diagnosis.
| Criterion | Benign | Malignant |
|---|---|---|
| General characteristics | ||
| Cellularity | Usually poor or moderate | Usually high |
| Cell to cell cohesion | Good with large defined clusters of cells | Poor with cell separation resulting in dissociated cells with cytoplasm or small groups of cells |
| Cell arrangement | Even, usually in flat sheets (monolayer) | Irregular with overlapping and three-dimensional arrangement |
| Cell types | Mixtures of epithelial, myoepithelial and other cells with fragments of stroma | Usually uniform cell population |
| Bipolar (elliptical) naked nuclei | Present, often in high numbers | Not conspicuous |
| Background | Generally clean except in inflammatory conditions | Occasionally with necrotic debris and sometimes inflammatory cells including macrophages |
| Nuclear characteristics | ||
| Size (in relation to red blood cell (RBC) diameter) | Small | Variable, often large, depending on tumour type |
| Pleomorphism | Rare | Common |
| Nuclear membranes (Pap stain) | Smooth | Irregular with indentations |
| Nucleoli (Pap stain) | Indistinct or small and single | Variable but may be prominent, large and multiple |
| Chromatin (Pap stain) | Smooth or fine | Clumped and may be irregular |
| Additional features | Apocrine metaplasia, foamy macrophages | Mucin, intracytoplasmic lumina |
(Modified from: GUIDELINES FOR NON-OPERATIVE DIAGNOSTIC PROCEDURES AND REPORTING IN BREAST CANCER SCREENING. NHSBSP Publication No 50 June 2001). |
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In many other European countries the diagnostic standardization all breast FNAs cytology specimens is coded using only four reporting categories:
- Inadequate
- Benign
- Suspicious and
- Malignant.
When European and U.K. classifications are compared there are no differences in next-step diagnostic procedure between U.K C3, C4 and C5 categories and suspicious/malignant since histopathological evaluation is required.