Histological and immunohistochemical evaluation of sentinel lymph nodes in breast cancer at a tertiary hospital in the Western Cape, South Africa.

Background: Breast carcinoma remains the most prevalent cancer among women, with over 300 000 deaths annually worldwide. Axillary lymph node status is essential for the clinical staging of breast carcinoma and remains the single most important predictor of disease-free survival in breast carcinoma.

Objective: To determine effective histological examination of sentinel lymph node (SLN) sections for the detection of metastatic breast carcinoma.

Methods: A prospective hospital-based study was done, including 20 patients with confirmed infiltrating breast carcinoma who underwent tumour excision or simple mastectomy as well as SLN biopsies. All the lymph nodes harvested were sectioned and embedded. Three sets of 15 consecutive serial sections were prepared from each case at one sitting, each measuring 3 - 5 μm in thickness and mounted on separate slides. Each set of 15 consecutive sections was grouped into three levels, each comprising 5 serial sections. The first 4 sections were stained with haematoxylin and eosin (H&E). The fifth section was stained for pancytokeratins, using MNF116.

Results: Twenty patients who met the inclusion criteria of this study underwent SLN biopsies and simple mastectomies or tumour excisions. Twelve SLNs of 11 patients contained metastatic carcinoma, all detected at level I, with one case requiring MNF116 immunohistochemistry staining, revealing metastatic carcinoma, measuring 0.08 × 0.08 mm (micrometastases). The size of metastatic carcinoma ranged between 0.08 × 0.08 mm (micrometastases) and 25 × 15 mm. Nine cases showed macrometastases, varying in size between 2 × 3.5 mm and 25 × 15 mm. Tumour sections of three patients with infiltrating carcinoma, of no specific type (NST), revealed lymphovascular invasion. The breast tumour sizes of these cases measured 40 × 25 mm (1/1 node involved), 30 × 20 mm (1/3 nodes involved) and 15 × 12 mm (1/1 node involved), respectively. Nine patients (19 nodes in total, mean 2.1, range 1 - 5) did not have demonstrable metastatic disease in the 45 sections of levels I - IX, including MNF116 on every fifth section. Patients with negative SLNs varied in age between 29 and 68 years and had breast tumour sizes ranging between 10 × 10 mm and 30 × 30 mm, respectively.

Conclusion: This study supports a conservative and cost-effective approach that comprises embedding of the entire SLN and the histopathological examination of four H&E-stained sections, which will usually demonstrate metastatic carcinoma. In the event of absence of metastatic carcinoma, immunohistochemical staining for pancytokeratin will detect tumour cells in a small percentage of cases. Examination of additional H&E- or pancytokeratin-stained sections is not cost effective. This finding can guide decisions pertaining to protocols for the histopathological assessment of SLN in breast carcinoma especially in resource-limited settings.