title: Rare breast cancer subtypes: histological, molecular, and clinical peculiarities.
abstract: Breast cancer encompasses a collection of different diseases characterized by different biological and pathological features, clinical presentation, response to treatments, clinical behavior, and outcome. On the basis of cell morphology, growth, and architecture patterns, breast cancer can be classified in up to 21 distinct histological types. Breast cancer special types, including the classic lobular invasive carcinoma, represent 25% of all breast cancers. The histological diversity of breast carcinomas has relevant prognostic implications. Indeed, the rare breast cancer group includes subtypes with very different prognoses, ranging from the tubular carcinoma, associated with an indolent clinical course, to metaplastic cancer, whose outcome is generally unfavorable. New approaches based on gene expression profiling allow the identification of molecularly defined breast cancer classes, with distinct biological features and clinical behavior. In clinical practice, immunohistochemical classification based on the expression of human epidermal growth factor receptor 2 and Ki67 is applied as a surrogate of the intrinsic molecular subtypes. However, the identification of intrinsic molecular subtypes were almost completely limited to the study of ductal invasive breast cancer. Moreover, some good-prognosis triple-negative histotypes, on the basis of gene expression profiling, can be classified among the poor-prognosis group. Therefore, histopathological classification remains a crucial component of breast cancer diagnosis. Special histologies can be very rare, and the majority of information on outcome and treatments derives from small series and case reports. As a consequence, clear recommendations about clinical management are still lacking. In this review, we summarize current knowledge about rare breast cancer histologies.
authors: Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy; and Istituto Oncologico Veneto IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico), Padova, Italy; Department of Pathology, University Hospital of Padova, Padova, Italy; Department of Medical and Surgical Sciences for Children & Adults, University of Modena and Reggio Emilia, Modena, Italy.
authors: Maria Vittoria
authors: MV
authors: Dieci
authors: Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy; and Istituto Oncologico Veneto IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico), Padova, Italy; Department of Pathology, University Hospital of Padova, Padova, Italy; Department of Medical and Surgical Sciences for Children & Adults, University of Modena and Reggio Emilia, Modena, Italy.
authors: Enrico
authors: E
authors: Orvieto
authors: Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy; and Istituto Oncologico Veneto IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico), Padova, Italy; Department of Pathology, University Hospital of Padova, Padova, Italy; Department of Medical and Surgical Sciences for Children & Adults, University of Modena and Reggio Emilia, Modena, Italy.
authors: Massimo
authors: M
authors: Dominici
authors: Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy; and Istituto Oncologico Veneto IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico), Padova, Italy; Department of Pathology, University Hospital of Padova, Padova, Italy; Department of Medical and Surgical Sciences for Children & Adults, University of Modena and Reggio Emilia, Modena, Italy.
authors: PierFranco
authors: P
authors: Conte
authors: Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy; and Istituto Oncologico Veneto IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico), Padova, Italy; Department of Pathology, University Hospital of Padova, Padova, Italy; Department of Medical and Surgical Sciences for Children & Adults, University of Modena and Reggio Emilia, Modena, Italy valentina.guarneri@unipd.it.
authors: Valentina
authors: V
authors: Guarneri
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000473:pathology* / Q000628:therapy; D002288:Adenocarcinoma, Mucinous / Q000235:genetics / Q000473:pathology* / Q000628:therapy; D014408:Biomarkers, Tumor / Q000096:biosynthesis; D001943:Breast Neoplasms / Q000145:classification / Q000235:genetics / Q000473:pathology* / Q000628:therapy; D018275:Carcinoma, Lobular / Q000235:genetics / Q000473:pathology / Q000628:therapy; D018276:Carcinoma, Medullary / Q000235:genetics / Q000473:pathology* / Q000628:therapy; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D011379:Prognosis; D035583:Rare Diseases / Q000235:genetics / Q000473:pathology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis; D011960:Receptors, Estrogen / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; C508053:ERBB2 protein, human
keywords: Cribriform carcinoma; Medullary carcinoma; Metaplastic carcinoma; Mucinous carcinoma; Pleomorphic lobular cancer; Tubular carcinoma