Medullary Carcinoma of the Breast

Cyclin E overexpression obstructs infiltrative behavior in breast cancer: a novel role reflected in the growth pattern of medullary breast cancers

Cell cycle deregulation is a prerequisite in tumor development and overexpression of cyclin E, a major G1-S regulator, is often observed in breast cancer and is further linked to poor prognosis. By overexpressing cyclin E in a retinoblastoma-inactivated breast cancer cell line, we induced significant alterations in the expression of genes associated with proliferation and cell adhesion. Rearrangements of the actin cytoskeleton in addition to increased adhesive properties, decreased motility, and invasive potential in functional assays, indicated an overall abrogated mobility. Consistent in vivo findings were obtained upon investigation of 985 primary breast cancers, where cyclin E-high tumors predominantly (67%) displayed a low infiltrative, pushing growth pattern. Furthermore, medullary breast cancers, a subtype defined by its pushing, delimited growth, exhibited a remarkable frequency of cyclin E deregulation (87%) compared with other histologic subtypes (5-20%). Taken together, our results suggest the novel role of cyclin E in modeling infiltrative behavior. The consequences of cyclin E overexpression in breast cancer seems to be multiple, including effects on proliferation as well as growth patterns, a scenario that is indeed observed in the archetype of cyclin E-overexpressing medullary breast cancers.

Histological type and syncytial growth pattern affect E-cadherin expression in a multifactorial analysis of a combined panel of sporadic and BRCA1-associated breast cancers

E-cadherin is a prominent factor in maintaining the epithelial architecture, and loss of its normal function is considered to be a key element in cancer invasion. In breast cancer, correlation between alteration of E-cadherin expression and histological type has been reported, but associations with other parameters remain uncertain. To refine these findings and to explore the biological significance of features thought to result from alterations of cell-to-cell adhesion systems, rare in sporadic cases but more frequent in BRCA1-associated breast cancers (BRCA1-BCs), we investigated E-cadherin expression by immuno-histochemistry in a combined panel of 214 breast cancers enriched in hereditary cases (176 sporadic cases and 38 BRCA1-BCs). Following multivariate statistical analysis using a logistic regression model, only 2 parameters were significantly associated with loss of E-cadherin expression: lobular histological type (p < 0.0001), in agreement with previous results, and syncytial growth pattern (SGP) (p = 0.01). The latter result provides a biological basis for SGP, the cardinal feature of medullary breast carcinoma.