Male secretory breast cancer: case in a 6-year-old boy with a peculiar gene duplication and review of the literature.

Purpose: Secretory breast cancer (SBC) is one of the rarest breast cancer (BC), representing the majority of BC in childhood. Nevertheless, it elicits a lot of interest both for the peculiar morphology and the characteristic genetic features. Currently, there is no consensus on optimal treatment strategy. Therefore, it is useful to report every case in order to establish treatment algorithms.

Methods: We describe the case of a 6-year-old boy diagnosed with a SBC, with peculiar genomic and immunohistochemical features. Moreover, we carried out a review of the literature in order to analyze the present state of knowledge about this rare entity.

Results: To the best of our knowledge, there are only 120 cases published in literature, only 32 in males and only 2 younger than 6 years. Furthermore, this one had peculiar genomic and immunohistochemical features. Indeed, even if SBC expresses basal-cell markers, our patient had a triple-negative tumor expressing both basal and luminal cell markers. Furthermore, the boy's genomic profile revealed not only positivity for the typical SBC's translocation t(12;15), but also for a 3q28 duplication, found in his father (healthy) and paternal grandfather (with a previous BC). None were positive for BRCA mutation. This locus includes only one gene encoding for a growth factor recently linked to Early Infantile Epileptic Encephalopathy-47 and Idiopathic ventricular tachycardia. Even if the literature does not provide evidence of a pathogenic role it is not possible to exclude a cancer-predisposing activity.

Conclusions: SBC is a rare type of BC, characterized by triple-negative features with an unexpectedly good prognosis. More data are needed to fully understand the behavior of this cancer and genomic profiling could be helpful in improving its diagnosis and management.