E cadherin is a useful immunostain in the diagnosis of lobular carcinoma (in situ and invasive)
It is negative in 90% of tumours
In those tumours where it is positive it shows a weak membrane pattern rather than the crisp strong membrane staining seen in NST carcinomas
As general guidance if you think the tumour is morphologically lobular report it as such whatever the E cadherin status unless it is really strong when you should look at the H&E again!
There is a growing literature on the use of beta catenin to assist in the diagnosis of E cadherin-positive lobular carcinomas:
These cases show a granular cytoplasmic so called 'Golgi' pattern of staining whereas NST cancers show a membranous pattern of staining
The accumulation of beta catenin within Golgi apparatus in the cytoplasm rather than its reaching the cell membrane reflects the dysfunctional pathway of cell adhesion molecule synthesis
See images below
20% of breast carcinomas are of special type and the majority of these are lobular carcinomas. Tubular and mucinous carcinomas occur next most frequently and thereafter
the remaining special types are seen infrequently. In order to make a diagnosis of a special type of carcinoma >90% of the tumour is required to show the particular pattern in question.
Special types of carcinoma should be distinguished from mixed carcinomas where the special type areas occupy between 50 and 90% of the tumour area with the remaining area being usually of no special type.
See also Common Cancers
It is recommended that special types of carcinoma are graded using the same criteria as no specicial type cancers.
These tumours, in their classical form, are characterised by a single file infiltrating pattern. Tumour cells are normally intermediate in size and a common finding is the presence of a squared off clear space between adjacent tumour cells. Cytoplasmic vacuolation is common and another frequently encountered feature is the presence of a rather granular eosinophilic cytoplasm. A number of variant forms are recognised (see link below).