THE IAC YOHOHAMA SYSTEM FOR REPORTING BREAST CYTOPATHOLOGY 1. Insufficient 2. Benign 3. Atypical 4. Suspicious of Malignancy 5. Malignant 1. INSUFFICIENT The smears are too sparsely cellular or too poorly smeared or fixed to allow a cytomorphological diagnosis. FNAB smears are regarded as adequate or inadequate based on the assessment of the material on the slides. The report should contain a statement that the material may not represent the lesion and further FNAB or CNB is required. Management If insufficient due to technical issues, the smear should be repeated to a maximum of three passes. If the insufficiency is due to the lack of sufficient cellularity to explain the clinical or imaging expected diagnosis, it should be repeated. If the imaging is indeterminate or suspicious, repeat FNAB or CNB is mandatory. If the imaging is regarded as benign or low-risk, imaging review may be regarded as appropriate and usually occurs at 3 to 6 months. 2. BENIGN A benign breast FNAB diagnosis is made in cases that have unequivocally benign cytological features, which may or may not be diagnostic of a specific benign lesion. The risk of malignancy of benign FNAB is 1 3%. Management Correlate triple test when available. A benign FNAB that correlates does not require any further biopsy and no specific recommendation is needed. If the clinical or imaging assessment is indeterminate and not explained by the cytology, the cytology should be reported as benign, and follow-up biopsy should be recommended. Follow-up for benign FNAB varies according to diagnosis. 3. ATYPICAL The term atypical in breast FNAB cytology is defined as the presence of cytological features seen predominantly in benign processes or lesions, but with the addition of some features that are uncommon in benign lesions and which may be seen in malignant lesions. Three major causes for atypical diagnoses: 1. Operator skill and FNAB technique (low cellularity, obscuring blood or u/s gel, forceful smearing causing crush artefact and dispersal, air-drying). 2. Interpretive problems due to overlapping features between proliferative lesions (UEH, ID papilloma & FA) and LG in situ lesions and LG invasive Ca. 3. Degree of training, experience, ongoing case load, and experience of the cytopathologist. The risk of malignancy in two Yokohama studies varied between 13% and 15.7 %. Other studies report 22 39%. The discrepancy is due to the variability in the definition and usage in literature. Management If due to a technical problem Repeat FNAB If sufficient material present triple test if either or both clinical or radiology are indeterminate or suspicious Repeat FNAB/CNB (if neither are of concern, management and follow-up varies, best discussed at MDT) 4. SUSPICIOUS OF MALIGNANCY The term suspicious of malignancy in breast FNAB is defined as the presence of some cytomorphological features which are usually found in malignant lesions, but with insufficient malignant features, either in number or quality, to make a definitive diagnosis of malignancy. The type of malignancy suspected should be stated whenever possible. Two studies using the Yokohama system report a risk of malignancy of 97.1% and 84.6%, respectively. Management Review radiology Further biopsy is an absolute requirement 5. MALIGNANT A malignant cytological diagnosis is an unequivocal statement that the material is malignant, and the type of malignancy identified should be stated whenever possible. The positive predictive value of a malignant breast FNAB should ideally be 100%. The reported range is 92 100%. Management Depends on the centre Essentially includes triple test with or without CNB, to plan neo-adjuvant therapy or surgery. Prognostic and treatment markers are done on cell block material in some centres, thereby excluding CNB prior to surgery. If axillary lymph nodes are palpable FNAB References 1. Field AS, Raymond WA and Schmitt FC. Preface: The International Academy of Cytology Yokohama System for Reporting Breast Fine-Needle Aspiration Biopsy Cytopathology. Acta Cytol 2019; 63(4): 255 256. 2. Field AS, et al. The International Academy of Cytology Yokohama System for Reporting Breast Fine-Needle Aspiration Biopsy Cytopathology. Acta Cytol 2019; 63(4): 257 273.
