Immunohistochemistry Applied to Breast Cytological Material

Area of Science:

• Cytopathology
• Oncology
• Breast Pathology

Background:

• Fine-needle aspiration biopsies (FNABs) are minimally invasive breast lesion diagnostic tools.
• FNABs are often considered inferior to core-needle biopsies for differentiating in situ from invasive carcinoma and for ancillary testing.
• Properly handled FNAB samples can yield sufficient material for immunocytochemistry (ICC).

Purpose of the Study:

• To review the literature on the utility of ICC in breast FNAB samples.
• To evaluate diagnostic and theranostic applications of ICC in various cytological preparations.
• To provide recommendations for optimizing ICC performance in cytological samples.

Main Methods:

• Literature review of published studies on ICC in breast FNABs.
• Analysis of different cytological sample types: smears, liquid-based cytology, and cellblocks.
• Evaluation of specific markers (p63, 34βE12, hormonal receptors, HER2, Ki-67) in cytological specimens.

Main Results:

• p63 and 34βE12 are promising for differentiating in situ from invasive breast lesions.
• Most diagnostic ICC markers perform comparably to tissue-based assays.
• Theranostic marker testing (hormonal receptors, HER2, Ki-67) is feasible in cytological samples, particularly cellblocks, with careful technique.
• Air-dried smears are not recommended; cellblocks offer greater versatility.

Conclusions:

• Breast FNABs, when processed correctly, are suitable for comprehensive ICC analysis.
• Cellblocks are preferred over cytology slides for maximizing diagnostic and theranostic information.
• Standardization of fixation and antigen retrieval is crucial for reliable ICC results in cytopathology.