Micronucleus Study on Breast Cytology Aspirate Smears and its Diagnostic Utility

Micronucleus is a small fragment of nucleus present in the cells which have undergone chromosomal damage. It is used as a biomarker of genomic damage.

We aim to study the presence of micronucleus on breast cytology smears and the use of scoring the micronucleus as an additional criteria for the classification of breast lesions with emphasis on borderline gray zone categories.

This is a cross-sectional retrospective descriptive study.

Retrospective analysis of breast cytology smears received over a period of 2 years formed the basis of the study. Micronucleus scoring was done by counting the number of micronuclei in 1000 epithelial cells under oil immersion and compared in the benign, adenosis, usual/atypical ductal hyperplasia, and the three grades of infiltrating ductal carcinomas.

Descriptive analyses and one-way analysis of variance was used for statistical analysis.

Of the 243 cases, the average statistically significant (P < 0.05) micronuclei scores of the benign (190), adenosis (7), usual (11)/atypical (5) hyperplasia, grade 1, 2, and 3 carcinomas (30) were 0.5, 2, 2.9, 6.6, 13.2, 20.6, and 27.5, respectively (the corresponding median scores were 0.5, 2, 3, 6, and 20, respectively). Micronucleus score of ≤1 had a high sensitivity (100%) and specificity (99%) in confirmation of benign cases. Micronucleus score of ≥5 and <10 had a moderate sensitivity (60%) but a high specificity of 99% in detecting atypical ductal hyperplasia. Micronucleus score of ≥10 had a high sensitivity (96%) and specificity (99%) of detecting carcinomas.

Micronucleus scores showed a gradual increase across the categories proving the gradual occurrence of genomic damage. Micronucleus scoring serves as an additional criterion for the diagnosis of breast lesions.