Clinical history: 77 year old male with a palpable mass in the left breast.
What is the most probable diagnosis?
Invasive solid papillary carcinoma
The carcinoma present is a circumscribed invasive carcinoma that is predominantly solid with course fibrovascular structures. There is no cystic component or delicate fibrovascular cores. Immunohistochemistry with the multiplex ADH5 cocktail confirms no evidence of any myoepithelial cells, either within the lesion, or encircling the lesion.
Solid papillary carcinoma usually presents in the 7th or 8th decade. They are histologically circumscribed solid nodules of neoplastic epithelial cells that are typically ovoid or spindle-shaped and may have a streaming pattern similar to the appearance of epithelial cells in usual ductal hyperplasia. The cells may also have endocrine features and be immunoreactive for chromogranin and synaptophysin. Intracellular and extracellular mucin production is also a frequent feature (although not in this case).These lesions are usually surrounded by a myoepithelial layer (thus historically considered a variant of DCIS), however in the absence of myoepithelial cells, and no foci of traditional invasion (jigsaw pattern/irregular borders/invading nests), according to the 2011 WHO working group this variant should still be regarded as in situ for staging and management purposes as it has an indolent course.