Neuroendocrine Tumors of the Breast

Abstract

Primary neuroendocrine tumors of the breast are a rare and underrecognized subtype of mammary carcinoma. Neuroendocrine tumors of the breast occur predominately in postmenopausal women. The tumors are subclassified into well-differentiated and poorly differentiated neuroendocrine tumors, and invasive breast carcinoma with neuroendocrine features. Well-differentiated tumors show architectural similarity to carcinoids of other sites but lack characteristic neuroendocrine nuclei. Poorly differentiated neuroendocrine tumors are morphologically identical to small cell carcinoma of the lung. Neuroendocrine differentiation, seen in up to 30% of invasive breast carcinomas, is most commonly associated with mucinous and solid papillary carcinomas. The diagnosis of neuroendocrine differentiation requires expression of the neuroendocrine markers synaptophysin or chromogranin. The main differential diagnosis is a metastatic neuroendocrine tumor from an extramammary site. Neuroendocrine tumors of the breast are treated similarly to other invasive breast carcinomas. Although no consensus has been reached on the prognosis, most studies suggest a poor outcome.

Liver metastasis of a neuroendocrine neoplasm of unknown primary origin in a female patient with a history of breast cancer

“…Primary neuroendocrine carcinoma of the breast (NECB) is a rare and underrecognised subtype of the mammary carcinoma [ 1 ]. It is considered to account for approximately 1% of all breast cancers and 1% of all neuroendocrine tumours.…”

Histology of Luminal Breast Cancer

“…Expression of synaptophysin and/or chromogranin A should be strong and extensive in NET of the breast. ER and PR are usually strongly positive, whereas HER2 is negative [101][102][103][104][105][106].…”

“…Depending on the size of tumor cells, small-cell and largecell NECs are distinguished. HR positivity is found in 30-100%, and HER2 is reported to be negative [103,104,[107][108][109][110].…”

Neuroendocrine breast carcinoma metastasis to the brain

“…Neuroendocrine tumours (NETs) are rare and usually affect lung, pancreas and gastrointestinal tract 1. Breast localisation is observed in less than 0.5% of cases 2 3. NETs rarely metastasise to the brain.…”

“…NBC was first described in 1977 and was characterised by the presence of positive neuroendocrine markers in over 50% of the tumour cells. According to the 2012 WHO classification, NBC was subclassified into well-differentiated NET, poorly differentiated neuroendocrine carcinoma and invasive breast carcinoma with neuroendocrine differentiation, regardless of the percentage of neuroendocrine markers 3…”