Usefulness of cytological approach for invasive breast cancer diagnosis compared with alternative intrinsic subtype classification approach

Abstract

In recent years, the treatment of invasive breast cancer (IBC) has been based on intrinsic subtype classification by gene expression profiling (GEP). Because GEP is very expensive for every single case of IBC, immunoprofiling has been widely used as an alternative method of classification. Although the opportunity of cytological examination has declined despite its advantages of being non-invasive, inexpensive, and time-saving, we evaluated the usefulness of the cytological approach for IBC diagnosis compared with the alternative intrinsic subtype classification based on immunohistochemistry. This study was performed on 97 cases of histopathologically confirmed IBC whose stamp preparations were available at the time of needle biopsy. We used six nuclear parameters with a value of 1 or 2, namely, the size of the nucleus, nucleus-to-cytoplasm ratio, nuclear irregularity, chromatin status, chromatin intensity, and degree of anisokaryosis. We also employed an architectural parameter with a value of 1, 2 or 3. The sum of each parameter is plotted on the basis of histological types classified by an alternative method. It was found that cases with a total score of less than 8 are highly likely to be in the luminal A-like group, whereas about 74% of IBC cases with a score of 13 or more are either in the luminal B-like (HER2-positive), HER2-enriched, or triple negative group. Our results suggest that the cytological method utilizing our seven parameters may be useful for the evaluation of the treatment and prognosis of IBC patients.