ABSTRACT
Breast cancer is not a single disease entity but is in fact a highly heterogeneous group of diseases with varied clinical outcomes and therapeutic options. This chapter discusses the World Health Organisation histological classification of invasive breast cancers diagnosed mainly by morphological patterns under light microscopy with synopses of relevant pathological details of the various histological subtypes and relevant clinical data. Invasive carcinoma NST, while being the most common stand-alone histological diagnosis in breast cancer, is really, in itself, a very heterogenous group of tumours. The frequency of mucinous carcinoma is approximately 2%, often occurring in the older age group, with a median patient age of 71 years. Metaplastic carcinoma is typically a triple-negative breast cancer and overall has been shown to have a worse prognosis than other breast cancer histological types.
