TABLE 2.
Definition of non-operative diagnostic categories.
| Cytological diagnostic categories | |
|---|---|
| United Kingdom/European Recommendation (6,13) | Recommendation of the International Academy of Cytology, Yokohama (15–17) (Risk of malignancy: ROM%) |
| C1: Inadequate (quantitatively and/or qualitatively) | Inadequate (2.4–4.58%) |
| C2: Benign lesion | Benign (1.2–2.3%) |
| C3: Atypical, probably benign | Atypical (probably benign) (13–15.7%) |
| C4: Suspicious of malignancy | Suspicious (of malignancy) (87.6–97.1%) |
| C5: Malignant (both in situ and invasive) | Malignant (99–100%) |
| Core biopsy categories (6) | |
| B1: Normal breast tissue/Uninterpretable | |
| B2: Benign lesion | |
| B3: A lesion with uncertain malignant potential (malignancy may be associated with ≤25% of cases in the group as a whole). | |
| The followings are typically included in this category | |
| – Some sclerosing lesions: radial scars, complex sclerosing lesions, sclerosing papillomas | |
| – Non-malignant papillary lesions that have not been completely removed | |
| – Lobular (intraepithelial) neoplasia (atypical lobular hyperplasia, classical LCIS; cf. B5a) | |
| – Atypical epithelial proliferation of ductal type (this name is recommended for atypical epithelial proliferation of ductal type found in core biopsies, as quantitative criteria for atypical ductal hyperplasia (ADH) cannot be evaluated in core biopsy samples, so the diagnosis of ADH is not possible on core biopsy) | |
| – Mucocele-like lesions | |
| – Cellular fibroepithelial lesions | |
| – Spindle cell lesions for which other classification is not possible based on the sample | |
| B4: Suspicious of malignancy | |
| B5: Malignant | |
| B5a: in situ carcinoma ( ductal carcinoma in situ, pleomorphic and florid lobular carcinoma in situ; compare with B3; note: the United Kingdom recommendation for florid lobular carcinoma in situ is B4) | |
| B5b: invasive breast carcinoma | |
| B5c: indeterminate, either an in situ or an invasive carcinoma | |
| B5d: other malignant process | |
Categories C2, B2 (benign) and C5, B5 (malignant) can be considered definitive diagnoses, but these should be interpreted only in a multidisciplinary environment together with imaging and clinical findings, in a “triple diagnostic system”. Diagnostic categories should not be used without a written opinion. Categories are primarily useful for statistical evaluation purposes and assist in patient management.