Myoepithelial cells in lobular carcinoma in situ: distribution and immunophenotype

Breast lesions with myoepithelial phenotype

Myoepithelial cells (MECs) constitute a continuous layer of cells surrounding the breast glands, localised between the epithelial cells (ECs) and the basal membrane. MECs play important roles in normal mammary gland as they produce basal membrane and stimulate secretion. During neoplastic transformation, MECs act as a barrier preventing stromal invasion. MECs themselves can undergo a great variety of changes, ranging from hyperplastic to metaplastic, to neoplastic, and giving rise to a wide spectrum of morphological pictures sometimes difficult to interpret on routine diagnoses. Several benign and malignant breast tumours can present features of MECs differentiation. As these latter tumours are quite infrequent, the purpose of the present study is to offer a review of the morphological spectrum of MECs lesions, with correlations to prognosis.

The morphologic spectrum of lobular carcinoma in situ (LCIS) observations on clinical significance, management implications and diagnostic pitfalls of classic, florid and pleomorphic LCIS

Lobular carcinoma in situ (LCIS) is a non-invasive proliferation of atypical dyscohesive epithelial cells characterized by loss or functional alteration of E-cadherin-mediated cell adhesion. The morphologic spectrum of LCIS encompasses classic (C-LCIS), florid (F-LCIS) and pleomorphic LCIS (P-LCIS), as recently defined by the World Health Organization (WHO) Expert Consensus Group. Atypical lobular hyperplasia (ALH) is also part of this spectrum.This article highlights the morphologic and immunohistochemical features of the three forms of LCIS and summarizes their management implications and prognosis, with emphasis on F-LCIS and P-LCIS.

Canine and feline in situ mammary carcinoma: A comparative review

Carcinoma in situ of the breast is a well-known entity in humans. In veterinary medicine, particularly in canine and feline mammary literature, there is no agreement whether the term in situ should be used to indicate a specific carcinoma histotype or the noninvasive status of a carcinoma of any histotype. Moreover, in the most recent histologic classification of mammary tumors published by the Davis-Thompson Foundation, it is suggested to abandon the term carcinoma in situ given the lack of standardized criteria defining this entity, replacing it with epitheliosis or ductal/lobular hyperplasia with severe atypia. This publication presents a critical review of the term in situ in human and veterinary medicine considering the evolution of the term over the years and its heterogeneous use by different authors, including variations in immunohistochemical markers for classification. This review aims to point out the lack of uniformity in the nomenclature and classification issues in veterinary medicine regarding the use of the term in situ, laying the ground for a process of standardization in future publications.

Rabbit monoclonal E-cadherin antibody: A cost-effective alternative to mouse monoclonal antibody in distinguishing ductal carcinoma in situ from lobular carcinoma in situ

Rabbit monoclonal antibody (RabMAb) demonstrates higher sensitivity without sacrificing specificity than mouse monoclonal antibody (MMAb). MMAb against E-cadherin stain is heavily utilized in distinguishing ductal carcinoma in situ (DCIS) from lobular carcinoma in situ (LCIS). We aimed to compare the E-cadherin stain using RabMAb vs MMAb in distinguishing DCIS from LCIS. One hundred and seventeen in situ breast carcinomas (55 DCIS, 58 LCIS, and 4 DCIS and LCIS) were studied. Sections from a representative block of each were stained with RabMAb [EP700Y] and MMAb [36B5]. Scanned images of stained slides were compared in tandem. All DCIS cases (59/59) showed comparable staining by RabMAb and MMAb. Comparable staining was also observed in all but one case of LCIS (61/62; 98%). One case of pleomorphic LCIS showed mostly complete, weak to moderately intense membranous staining with RabMAb and fragmented, weak membranous staining with MMAb. Consistently better staining quality was observed in slides stained by RabMAb vs MMAb. RabMAb and MMAb against E-cadherin were diagnostically equivalent with the exception of one case where RabMAb may have led to diagnostic misinterpretation. However, the not insignificant cost savings and easier interpretation using RabMAb may justify the risk of misinterpretation of increased staining in rare cases, largely avertable with proper training.