Special Types of Invasive Breast Cancer, With Clinical Implications

Analysis of invasive breast cancers by histopathology has generally revolved around the analysis of individual characteristics such as nuclear pleomorphism and/or gland formation (grading) or categorization by specific histologic patterns (special type carcinomas). Recognition of special types of invasive breast carcinoma allows for the identification of women with an extremely good prognosis often approaching or equaling that of the general population of the same age (with unique problems for medullary). The distinguishing features of special types of breast cancer are present in complete or classic form in the pure examples of these cases, and the features recognizing these types may be present in lesser degrees in many carcinomas of no special type or not otherwise specified in which they often have important clinical correlates other than strong indicators of survival, such as recognizing the diffusely invasive feature of lobular and lobular-like cancers. Many other features have been noted as contenders for types of breast cancer (such as squamous, cystic, clear cell, histiocytoid, and lipid rich). These terms are not discussed here because they have no special clinical correlates relevant to diagnosis or prognosis. It should be reemphasized here that combined histologic grade (Nottingham system favored) with nuclear, glandular, and mitotic evaluation is expected by most authorities for clarification of diagnosis in all but rare, pure medullary cancers. (5, 13, 14, 27) The Nottingham grade 11 interacts with nodal status to produce a very strong prognostic index. The mitotic count may be the most important part of the grading system, certainly for prognosis within 5 years of diagnosis. (22, 26)