Clinical history: 89 year old female with mass lesion on screening mammogram.
What is the diagnosis?
Solid papillary carcinoma of the breast
Microscopically on low power we see a very well circumscribed lesion. On medium power, we can see solid sheets of cells separated by fibrovascular cores, without any significant infiltration. On high power, we do not see a myoepithelial cell layer, and this was confirmed with immunohistochemistry.
Solid papillary carcinoma is a rare and controversial entity. There is still debate regarding whether these lesions should be considered in situ or invasive. The majority of cases, like this one, do not have any detectable myoepithelial cells.
These tumors, when lacking obvious foci of typical invasion, have an excellent prognosis with adequate surgical excision. They are typically found in older women, and when associated conventional invasive carcinomas are present, they usually contain mucinous or neuroendocrine-like features.