Background Metaplastic carcinoma of the breast consists of both invasive ductal carcinoma and metaplastic carcinoma. This rare subtype of cancer has a poor prognosis. The development of metaplastic breast cancer and relationship with BRCA1 are not well known. Here, we report a rare case of germline BRCA1 mutation-positive breast cancer with chondroid metaplasia. Case presentation A 39-year-old Japanese woman with a family history of breast cancer in her mother and ovarian cancer in her maternal grandmother consulted at our hospital with a left breast mass. Needle biopsy for the mass was performed, leading to a diagnosis of invasive breast cancer with chondroid metaplasia. We performed left mastectomy + sentinel lymph node biopsy + tissue expander insertion and replaced with a silicone implant later. Pathological examination revealed that the patient had triple-negative breast cancer. Four courses of doxorubicin+ cyclophosphamide therapy were performed as adjuvant therapy after surgery. We performed genetic counseling and genetic testing, and the results suggested the germline BRCA1 mutation 307 T> A (L63*). She has currently lived without a relapse for 2 years post-surgery. Conclusions There have been only 6 cases of metaplastic breast carcinoma with germline BRCA1 mutations including our case. Patients with BRCA1 mutations may develop basal-like subtypes or M type of triple-negative breast cancer besides metaplastic breast cancers.

中文翻译：

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乳腺化生性癌和 BRCA1 种系突变：病例报告和综述

背景 乳腺化生性癌包括浸润性导管癌和化生性癌。这种罕见的癌症亚型预后较差。化生性乳腺癌的发展及其与 BRCA1 的关系尚不清楚。在这里，我们报告了一例罕见的胚系 BRCA1 突变阳性乳腺癌伴软骨样化生。病例介绍 一位 39 岁的日本女性，母亲有乳腺癌家族史，外祖母有卵巢癌病史，因左侧乳房肿块来我院就诊。对肿块进行了针刺活检，诊断为具有软骨样化生的浸润性乳腺癌。我们进行了左侧乳房切除术 + 前哨淋巴结活检 + 组织扩张器插入，后来更换为硅胶植入物。病理检查显示该患者患有三阴性乳腺癌。手术后进行了四个疗程的多柔比星+环磷酰胺治疗作为辅助治疗。我们进行了遗传咨询和基因检测，结果表明种系 BRCA1 突变 307 T> A (L63*)。目前，她在手术后 2 年没有复发。结论 包括我们的病例在内，仅有 6 例发生胚系 BRCA1 突变的化生性乳腺癌。除了化生性乳腺癌，BRCA1 突变患者可能会发展为基底样亚型或 M 型三阴性乳腺癌。结果表明种系 BRCA1 突变 307 T> A (L63*)。目前，她在手术后 2 年没有复发。结论 包括我们的病例在内，仅有 6 例发生胚系 BRCA1 突变的化生性乳腺癌。除了化生性乳腺癌，BRCA1 突变患者可能会发展为基底样亚型或 M 型三阴性乳腺癌。结果表明种系 BRCA1 突变 307 T> A (L63*)。目前，她在手术后 2 年没有复发。结论 包括我们的病例在内，仅有 6 例发生胚系 BRCA1 突变的化生性乳腺癌。除了化生性乳腺癌，BRCA1 突变患者可能会发展为基底样亚型或 M 型三阴性乳腺癌。