Breast cancer is the world's most prevalent cancer [1]. Multiple studies have shown that a delay in the treatment plan contributes to pre-operative stress experienced by patients [[2], [3], [4]]. In patients with benign lesions, quick diagnosis reduces anxiety [5], and in patients with malignant lesions, rapid confirmation expedites subsequent diagnosis and treatment planning. Therefore, European guidelines call for rapid confirmation or exclusion of breast cancer within 24–48 hours [6]. Accurate decision making and treatment planning, however, not only requires differentiating between benign and malignant lesion but also determination of molecular profile.

Various techniques for same day diagnosis of breast cancer exist, however none of these determine receptor status in clinical practice. Fine Needle Aspiration Biopsy (FNAB) is the fastest technique which makes it possible to make a diagnosis within an hour. However, due to the varying reported sensitivity, specificity and conclusiveness of this method, most clinics prefer Core Needle Biopsy (CNB) [[7], [8], [9]]. Although this method has a longer processing time, it is considerably more accurate [[10], [11], [12], [13], [14], [15]]. Currently, CNB is seen as the gold standard in assessing solid breast lesions [16,17]. In 2013, an accelerated method of CNB processing was developed, allowing for same day histologic diagnosis [18]. In an attempt to further expedite diagnosis while maintaining accuracy, Core Wash Cytology (CWC) was developed as an adjunct to CNB. In CWC, cytology and histology are combined, resulting in improved accuracy and a provisional same day diagnosis [19].

Previous studies have explored assessment of the expression of hormone receptors in cytology of breast cancer lesions using immunocytochemistry (ICC) with varying accuracy, without mention of the required timeframe to establish receptor status [[20], [21], [22], [23], [24]]. To our knowledge, no series validating or evaluating immunocytochemistry (ICC) to establish receptor status in Core Wash Cytology (CWC) has been published.

We hypothesize that the use of ICC on formalin fixed CWC can result in improved accuracy of the assessment of receptor status. Receptors of particular importance for clinical decision making are: estrogen (ER), progesterone (PgR) and human epidermal growth factor receptor 2 (HER2neu). These receptors have prognostic and predictive importance in decision making on further loco-regional and systemic (neo-)adjuvant therapy [25].

In recent years, neoadjuvant systemic treatment (NAT) has become an important part of breast cancer therapy. Decisions regarding the type of NAT are based upon the expression of the aforementioned receptors in the tumor. Timely knowledge of this status could expedite aforementioned decisions within the framework of a same-day breast cancer clinic.

The aim of the study is to determine feasibility and accuracy of determining receptor status using immunostained Core Wash Cytology (ICWC). Results were compared to the receptor expression on the CNB, which is the present diagnostic standard.