Endocrine Abstracts

Neuroendocrine tumours presenting in the bronchial or gastrointestinal tract often present with metastatic disease. Whereas well recognised sites of metastases include liver, lymph nodes and bones, they can also arise in unusual locations sometimes causing difficulties in diagnosis. The breast is an uncommon site for neuroendocrine tumour metastasis with estimates that it represents 0.1% of all breast tumours. Due to the low incidence of these neoplasms and due to difficulties in histopathological diagnosis, patients may be misdiagnosed. We present a series of cases of patients with neuroendocrine metastases to the breast highlighting issues in their diagnosis and subsequent management including; A 39 year old with an ACTH producing bronchial NET presenting with a breast lump, Subsequent imaging and biopsies under her local breast team were reported as invasive lobular cancer in both breasts. Treated with bilateral mastectomy however further IHC analysis showed neuroendocrine markers on the tumour cells resulting in a re-categorisation as metastatic NET. A 51 year old lady with germline BRCA 2 mutation. Previous bilateral mastectomy and axillary node clearance for breast cancer. Multiple lung nodules detected several years later. Diagnostic wedge resection and histopathology diagnosed atypical pulmonary carcinoid. Subsequent slow growth in lung nodules without treatment. New left sided axillary lymph node 2019. Biopsy revealed breast carcinoma. Gallium 68 PET/CT – no abnormal uptake in the lung lesions. Review of all breast and lung histology confirms breast metastases to lungs rather than bronchial carcinoid. The cases will be presented highlighting the diagnostic challenges with respect to similarities in histomorphology and immunohistochemistry and put in context with the current literature.