Case Report of Histiocytoid Invasive Lobular Carcinoma.

The histiocytoid variant of invasive lobular carcinoma (ILC) is a rare subtype of breast cancer that can be challenging to diagnose and aggressive in nature. It is often diagnosed after the disease has metastasized. This report describes a case of a six-centimeter ILC of the histiocytoid subtype. The patient is a 66-year-old female who was initially told that she had dense breast tissue. At the time of diagnosis, she had a large mass and was found to have metastases to the axillary lymph nodes and vertebra. She was started on chemotherapy and immunotherapy, but has since developed multiple new lesions to her spine, rib, and femur. This case highlights the aggressive nature of this variant, which progressed while during treatment.