Abstract
INTRODUCTION AND IMPORTANCE: Pleomorphic carcinoma of the breast is extremely rare, accounting for <0.1 % of breast malignancies. It has a poor prognosis, but its clinicopathologic features are not well characterized. CASE PRESENTATION: A 49-year-old woman was diagnosed with bilateral breast cancer (rt: cT2cN0M0 cstageIIA, lt: cT2cN1M0 cstageIIB) and its intrinsic type was non-luminal type (right breast) and lumina A-like (left breast). After neoadjuvant chemotherapy, the patient achieved pathologic partial response and underwent breast-conserving surgery with axillary lymph node dissection and radiotherapy. After 6 years and 7 months, local recurrence in the right breast was observed, and mastectomy was performed. However, after 4 weeks, metastasis to the contralateral breast was found, and a further 13 weeks later, 70 % of the thoracic cavity was occupied by metastatic pleural tumors. Pathological findings suggested pleomorphic carcinoma. The patient passed away 25 weeks later after the diagnosis of local recurrence. CLINICAL DISCUSSION: Pleomorphic carcinoma could represent an extreme end of dedifferentiation of invasive breast carcinoma of no special type or part of the differentiation of metaplastic spindle cell carcinoma. It is also important to differentiate this from malignant tumors such as sarcomas with giant cells or spindle cells, and metastatic tumors. Pathological diagnosis requires lack of heterologous non-epithelial components, and strong immunostaining with epithelial markers. CONCLUSION: When a rapidly growing breast mass is encountered, pleomorphic carcinoma should be considered as one of diagnostic candidate. More case accumulation and analyses are awaited to further characterize this carcinoma.