The expression of neuroendocrine markers in invasive lobular carcinoma

Abstract

Neuroendocrine breast tumours are classified as a rare form of breast cancer which constitutes less than 1% of neuroendocrine neoplasms. These tumours are derived from cells of neuroendocrine origin that require immunohistochemical stains to confirm neuroendocrine (NE) differentiation. Neuroendocrine breast tumours are more common in postmenopausal women between the sixth and seventh decade of life. The standard markers used to detect neuroendocrine differentiation include Synaptophysin and Chromogranin A due to the high sensitivity and specificity. Studies have shown that neuroendocrine differentiation occurs in 30% of invasive breast cancers and is more commonly found in mucinous carcinomas, solid papillary carcinomas and invasive ductal carcinomas. There is limited information on NE differentiation in invasive lobular carcinoma (ILC). Through the use of immunohistochemical techniques, the incidence of neuroendocrine differentiation in ILC was determined. In this study, 108 cases of previously diagnosed invasive lobular carcinoma (ILC) with varying grades (Grade I, Grade II, Grade III) and Metastatic Lobular carcinomas were used to determine which cases show neuroendocrine differentiation through the expression of the routinely used neuroendocrine markers: CD56, Chromogranin A, INSM-1, and Synaptophysin. As a control group, 16 cases of Neuroendocrine breast neoplasms were used. It was concluded that CD56 was not a reliable marker to detect NE differentiation in ILC due to the non-specific staining of normal breast tissue in 84.2% of the lobular cases. There was no expression of Chromogranin A in the lobular and metastatic cases. In addition, INSM-1 and Synaptophysin were the best markers to detect neuroendocrine differentiation in the control group. In conclusion, neuroendocrine differentiation was detected in 3.70% of the lobular and metastatic lobular cases.