Subtypes of Breast Cancer in Lao P.D.R.: A Study in a Limited-Resource Setting

Aim: The purpose of this study is to evaluate the prevalence of the immunohistochemical subtypes of breast canceramong Lao women by using immunohistochemistry (according to the St. Gallen 2017 guidelines) and to study theircorrelation to clinicopathological features in order to help guide better treatment plans for patients. Materials andmethods: Formalin-fixed and paraffin embedded tissue blocks of 76 cases of primary invasive breast cancer wereretrieved from the University of Health Sciences, Vientiane, Lao PDR, from 2013 to 2016. Patients’ information andprevious histological reports were reviewed. Immunohistochemistry was done using antibodies against estrogen receptor(ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2/neu) and Ki-67 (MIB-1). Results:The mean age of the patients was 49 years, and the major histologic type was invasive ductal carcinoma, NOS (90.7%).The proportion of each subtype was hormone receptor-positive and HER2-negative, 44.7%; hormone receptor-positiveand HER2-positive, 3.9%; hormone receptor-negative and HER2-positive, 13.2%; and triple-negative, 38.2%. ER waspositive in 40.8% of the cases, while PR was positive in 47.4%. More than half of the cases were poorly differentiatedcancer (65.8%), followed by moderately differentiated (34.2%). Tumors presented with pT2 (60.5%), followed by pT3(25.0%) and pT4 (7.9%). Conclusion: Breast cancer among Lao women is characterized by a large percentage of thetriple-negative subtype that is less susceptible to hormonal treatments. The empirical treatment with tamoxifen shouldbe reconsidered since it would be less effective to these patients. More importantly, basic pathology services shouldbe the first requirement in Lao PDR in order to provide adequate care.