Non-diagnostic smears in aspiration cytology of palpable breast lumps

The cytologic diagnoses of a wide variety of breast diseases have been described in the literature and cytologic appearances of some of these are not characteristic. Technical problems during aspiration and smear preparation influence the final diagnosis, therefore, even at best hands a non-diagnostic category is to be expected. The objectives of this study were to determine the frequency of non-diagnostic reports and to assess the source of indecisiveness. This study is based on a retrospective analysis of breast aspirates signed out by the first author over a period of 18 months. The smears with non-diagnostic reports were correlated with the available histologic follow-up to identify the problem area. Forty-eight (9.1%) out of the 527 samples were non-diagnostic and within the recorded range of 6.9% to 20%. Of those 48 in the non-diagnostic category, 30 (62.5%) had histological follow-up. There were 11 (36.7%) malignant lesions and 19 (63.3%) benign lesions. In 23 cases (77%) pure interpretative problems and in 3 cases (10%) pure technical problems were responsible for the non-diagnostic reports. In 4 cases (13%) both factors contributed to the non-diagnostic report. Thirteen of the 30 (43%) lesions were cytologically suspected to be malignant. Of these 13.9 (69%) were found to be malignant while only 4 were benign; thus non-diagnostic but suspicious lesions are more likely to be malignant. The commonest cytologic features responsible for problems at interpretation were high cellularity (37%), cell discohesion (30%), large nuclei and nucleoli (30%) and the small size of the cells (40%). Inadequate or low cell yield (86%), inadequate clinical history (14%) and poor staining (14%) contributed to technical problems. The cytologic diagnosis of breast lesions such as fibromatosis, complex sclerosing lesions, papillary lesions, angiosarcoma and low nuclear grade in situ and invasive carcinomas can be difficult and the cytologic criteria for these diagnoses need further evaluation.