The role of laboratory processing in determining diagnostic conclusiveness of breast fine needle aspirations: conventional smearing versus a monolayer preparation.

AIM

To compare breast fine needle aspiration (FNA) specimens prepared by conventional smearing (CS) versus monolayer preparation (MP), with respect to the conclusiveness of the cytopathological diagnosis.

METHODS

From 1992 to 1996, aspirators prepared aspirates themselves by direct smearing onto 2-4 slides. From 1999 to 2003, aspirate preparation was performed in the laboratory, creating a MP, using a Hettich cytocentrifuge. FNA diagnoses were categorised into inadequate (C1), benign (C2), atypical (C3), suspicious for malignancy (C4) and malignant (C5). The reference standard constituted histological follow-up. A conclusive FNA diagnosis was defined as C2 in lesions benign on follow-up and C5 in lesions malignant on histology.

RESULTS

From 1992 to 1996, 692 aspirates were processed by CS, whereas from 1999 to 2003, 1301 aspirates were processed by MP. More FNA were ultrasound-guided in the MP group (85.6% versus 21.5%, p<0.001). When compared with CS, MP-prepared FNA had conclusive diagnoses significantly more often (72.8% versus 58.5%, p<0.001). This effect remained significant when corrected for the difference in ultrasound guidance (adjusted odds ratio 1.7, 95% confidence interval 1.3 to 2.2, p<0.001), and was larger for malignant lesions than for benign lesions (51.7% versus 79.9%, p<0.001).

CONCLUSION

Patients presenting with breast lesions can more often be offered a same-day, conclusive cytopathological diagnosis when FNA are prepared by a manual MP processing technique.