Tipos histológicos poco frecuentes de carcinoma infiltrante: carcinomas metaplásicos, carcinomas apocrinos y neoplasias neuroendocrinas de la mama

Abstract

Metaplastic carcinomas (MCs), primary neuroendocrine cancers of the breast (NECB) and apocrine carcinomas (APCs), have undergone several changes in their definition and nomenclature over the years, and are therefore a group of special interest for discussion and updating.MCs are a heterogeneous group from a histopathological and prognostic point of view, which require appropriate sampling and a wide panel of immunohistochemical techniques to identify them. There are different subtypes with highly variable morphological characteristics and marked intra- and inter-tumoural heterogeneity. These include low-grade adenosquamous carcinoma, fibromatosis-like MC, squamous cell carcinoma, spindle cell carcinoma, MC with heterologous mesenchymal differentiation, and mixed MC. They mostly have a triple-negative immunophenotype and as a group have a poor prognosis, and poor results with the available targeted therapies.APC has a characteristic histological appearance and immunophenotype (RA+, ER-, PR-, HER2+/−, GCFP+, AMACR+), which should show predominantly in the tumor. The molecular profile or apocrine molecular signature (luminal-AR/apocrine molecular carcinoma) does not always coincide with the histopathological diagnóstico of APC. Targeted anti-androgen therapy is a therapeutic target with promising results.NE differentiation can be found in different breast tumors, either of non-special subtype, or in subtypes such as hypercellular mucinous carcinoma or solid papillary carcinoma. The diagnóstico of primary breast NEN requires morphological and immunophenotypic NE differentiation in >90% of tumor cells, first having ruled out the metastatic nature of the lesion. Two types of primary breast NEN are distinguished: NE tumor (NET) and NE carcinoma (NEC), the latter being either large cell or small cell. The prognosis and treatment of these lesions is currently like that of other infiltrating breast carcinomas according to histological grade and stage at diagnóstico.