The rare entity of bilateral and unilateral neuroendocrine metastases to the breast: a case series and literature review

Abstract

Introduction Primary neuroendocrine neoplasms (NENs) in the breast are very rare. Until 2011, the prevalence was 0.1% of all breast lesions and 1% of all NENs, whereas metastatic breast NENs represent 1%–2% of all breast tumours. However, it seems that over the last 5 years the diagnostic frequency of breast NENs has increased, probably for more alert specialists and advanced diagnostic tools, leading to a prevalence of 2%–5% of diagnosed breast cancers, mostly in the elderly population. Breast metastases from extramammary malignancies are uncommon and bilateral ones are even more uncommon, with few reported in the literature. We describe four clinical settings of breast metastases from different NENs and the multidisciplinary approach for diagnosis and treatment. Methods Four patients were found to have NEN primaries metastasised to the breast. A literature review was conducted to identify similar cases and characterise breast metastases from neuroendocrinal tumors (NETs). Results Two patients presented with bilateral breast metastases (one with well-differentiated panNET and another with atypical lung carcinoid) and two had unilateral (one with moderately differentiated lung NET and one with atypical lung carcinoid). There are about 13 cases of NEN breast metastases reported in the English literature. The ileum is the most common primary site, followed by the appendix, duodenum, pancreas and lung. Conclusion Breast lesions from extramammary primary often pose a diagnostic challenge, since a breast nodule can be the first and often the only presentation of the disease. However, differentiating between primary and secondary NEN breast lesions is essential, owing to different clinical management and prognosis.

Bilateral breast metastases as the first manifestation of an occult pancreatic neuroendocrine tumor

“…In particular, bilateral breast metastases from a distant NET represent an extremely rare manifestation with just less over 13 cases described in literature and only two cases originating from PNET are described [8 , 20] .…”

“…Breast metastases from NETs represent an important diagnostic challenge for practitioners because of the difficulty to differentiate from a primary breast carcinoma or even from benign breast lesions [8] .…”

“…Although recent data suggests that, probably, breast metastases from NETs are more frequent than what was thought, they remain a rare phenomenon with no more than 200 cases published in literature [8 , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] . The most common primary site of metastatic NET breast lesions is represented by the ileum, followed by appendix, duodenum, pancreas, lung and ovary [8 , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] .…”

“…Although recent data suggests that, probably, breast metastases from NETs are more frequent than what was thought, they remain a rare phenomenon with no more than 200 cases published in literature [8 , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] . The most common primary site of metastatic NET breast lesions is represented by the ileum, followed by appendix, duodenum, pancreas, lung and ovary [8 , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] . With regard to cases of bilateral breast metastases from a distant primary NET, there are less than 15 cases reported in literature and, in particular, to the best of our knowledge, only two cases originating from a pancreatic neuroendocrine tumor (PNET) are reported [8 , 20] .…”

“…The most common primary site of metastatic NET breast lesions is represented by the ileum, followed by appendix, duodenum, pancreas, lung and ovary [8 , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] . With regard to cases of bilateral breast metastases from a distant primary NET, there are less than 15 cases reported in literature and, in particular, to the best of our knowledge, only two cases originating from a pancreatic neuroendocrine tumor (PNET) are reported [8 , 20] .…”