Letter to editor/comment : Metaplastic carcinoma of the breast: Prognosis and response to systemic treatment in metastatic disease

Abstract

I read with a great interest a recently published clinical study of Takala et al 1 on metaplastic carcinoma of the breast. The authors explored 78 patients with the diagnosis of metaplastic carcinoma in the period 2002-2016. In line with previous studies, the authors confirmed predominantly triple-negative phenotype of metaplastic carcinomas (85%) exhibiting a poor therapeutic response with an aggressive clinical course and poor outcome.

Two things are worthy of further discussion: First, 12% of the patients were estrogen receptor (ER)-positive, eight of which received adjuvant endocrine therapy. I would appreciate more information from the authors regarding the percentage of ER positivity in these metaplastic carcinomas and a potential response to endocrine treatment. It is well known that most metaplastic carcinomas are ER-negative and if ER-positive, the percentage of positive cancer cells is usually low (range, 1%-10%). This fact may substantially affect the response to endocrine therapy, as the patients with lower ER positivity in their breast cancers are less responsive to anti-ER treatment modalities.