Metaplastic
carcinoma is a rare histological
malignancy, often triple-negative, and has a poor prognosis. Here, we report a case of
breast cancer in which the primary lesion degenerated into
squamous cell carcinoma(triple negative)after
drug treatment for invasive
ductal carcinoma(
Luminal type). The patient was a 41-year-old woman who was diagnosed with Stage Ⅳ left
breast cancer T2N2bM1(HEP)(ER 90%, PR 70%, HER2 2+, FISH-)at another hospital and participated in the PATHWAY study(
tamoxifen plus
goserelin plus
palbociclib/placebo). Since the primary lesion and liver
metastasis increased in size, the study was discontinued after 8 weeks. She was treated at our hospital thereafter, with
capecitabine plus
cyclophosphamide,
palbociclib plus
fulvestrant plus
leuprorelin,
paclitaxel plus
bevacizumab,
eribulin, EC
therapy, and
docetaxel. However, both the primary lesion and liver
metastasis increased. In particular, the increase in primary lesion size was remarkable, and the QOL significantly reduced due to
bleeding and exudation. Biopsy performed during
docetaxel treatment revealed metaplastic/
squamous cell carcinoma(ER-, PR-, HER2 0, Ki-67 90-100%)histopathological findings. BRCA and
microsatellite instability tests were negative, and PDL1 expression was less than 1%. Although Mohs
ointment was used,
tumor bleeding, exudate, and stink were poorly controlled, and the patient experienced painful symptoms due to the weight of the
tumor. Therefore, left
mastectomy plus pectoralis major muscle resection was performed. The patient died one month after the operation.