Evaluating Estrogen Receptor Immunohistochemistry on Cell Blocks From Breast Cancer Patients in a Low-Resource Setting

Breast cancer biomarker assessment is critical in determining treatment and prognosis. In Tanzania, immunohistochemistry (IHC) is limited to surgical specimens and core biopsies. However, performing IHC on fine-needle aspiration biopsy cell blocks would offer numerous advantages. To compare the performance between estrogen receptor (ER) IHC performed at Muhimbili National Hospital (MNH) in Tanzania and ER IHC performed at University of California, San Francisco (UCSF), to demonstrate feasibility of performing IHC using cell blocks in Tanzania. Patients with breast masses were recruited prospectively from the fine-needle aspiration biopsy clinic at MNH. Estrogen receptor IHC results on cell blocks, performed at both MNH and UCSF, and corresponding tissue blocks, performed at MNH, were compared to determine concordance. Eighty-six cell blocks were evaluated by ER IHC at MNH, with 41 of 86 (47.7%) positive and 45 of 86 (52.3%) negative. Among 65 UCSF and MNH cell block pairs, overall ER IHC concordance was 93.8% (61 of 65) and positive concordance was 93.5% (29 of 31) (κ = 0.88, P > .99). Among 43 paired UCSF cell blocks and MNH tissue blocks, overall ER IHC concordance was 88.3% (38 of 43) and positive concordance was 90.5% (19 of 21) (κ = 0.77, P > .99). We compared 62 MNH cell block and tissue block pairs. Overall ER IHC concordance was 90.3% and positive concordance was 87.9% (κ = 0.81, P = .69). Pairwise comparisons between ER IHC at MNH, on cell blocks and tissue blocks, with ER IHC at UCSF on cell blocks showed excellent concordance. We demonstrate that ER IHC on fine-needle aspiration biopsy specimens can be implemented in resource-constrained settings.