间质性乳腺癌（MBC）是一种罕见的肿瘤群体，常表现为三阴性。MBC占所有乳腺癌的比例不到1％，棘细胞变体仅占不到0.5％。虽然罕见，但棘细胞癌是西方世界最常见的亚型。它具有更具侵袭性的生物学行为，与三阴性乳腺癌相比，复发和死亡的疾病风险增加。由于疾病的稀有性，MBC的治疗指南还没有出现。相反，治疗是基于对不同组织的侵袭性乳腺癌和间叶性癌症的成功来推论的。我们报道了男性乳腺棘细胞癌的首例病例报告，该病例接受了KEYNOTE-522方案的治疗。该治疗包括第一阶段的每3周一次的pembrolizumab（剂量为200毫克），加上紫杉醇和卡铂，以及第二阶段的四个循环，使用多西紫杉醇环磷酰胺联合pembrolizumab。©作者（2023）。

Metaplastic Breast Cancer (MBC) is a rare group of tumors often presenting as triple-negative. MBC accounts for less than 1% of all breast cancers with the spindle cell variant comprising less than 0.5%. While rare, spindle cell carcinoma is the commonest subtype in the western world. It has a more aggressive biological behavior with increased risk of recurrence and death due to disease compared to triple negative breast cancers. There is no treatment guideline for management of MBC due to the rarity of the disease. Instead, treatment is theorized based off success with other types of aggressive breast and metaplastic cancers of different tissue. We present the first known case report of male spindle cell carcinoma of the breast treated with KEYNOTE-522 regimen. Therapy included a first phase with pembrolizumab (dose of 200 mg) every 3 weeks plus paclitaxel and carboplatin and second phase, with four cycles of pembrolizumab with doxorubicin-cyclophosphamide.© The Author(s) 2023.