Primary Breast Carcinoid With Metastasis and Ectopic ACTH Secretion: A Diagnostic DilemmaBaessa, Ebtesam Mohammad MBBS, MRCP, FRCP(Edin), ABIMAuthor Information From the Department of Endocrinology, Dammam Medical Complex, Dammam, Kingdom of Saudi Arabia. Reprints: Ebtesam Baessa, MBBS, MRCP, FRCP, ABIM, Head Section of Endocrine & Diabetes Department, Dammam Medical Complex, PO Box 250, Dammam, Post code 31411, Kingdom of Saudi Arabia. E-mail: [email protected] The Endocrinologist: May/June 2010 - Volume 20 - Issue 3 - pp 96-97 doi: 10.1097/TEN.0b013e3181dee646 Buy Metrics Abstract Carcinoid tumors most frequently develop in the gastrointestinal tract but have been described in many organs of the body. Primary neuroendocrine carcinoma of the breast is rare-only 31 cases have been reported in literature. Immunohistochemical examination showing expression of chromogranin and/or synaptophysin confirms evidence of neuroendocrine differentiation. In primary neuroendocrine carcinoma of the breast, more than 50% of the cell population shows neuroendocrine differentiation. Foci of neuroendocrine differentiation usually can be seen in breast carcinoma and are reported to be present in about 2% to 5% of breast cancer cases. Carcinoid tumor metastatic to the liver from the breast is very unusual. We report a case in which the patient underwent breast lumpectomy with axillary dissection. The tumor initially was diagnosed as an infiltrative lobular carcinoma with axillary lymph node metastasis. Re-examination of the breast tumor histopathology, however, proved it to be a primary carcinoid tumor. © 2010 Lippincott Williams & Wilkins, Inc.