Breast cancer is a global health problem – it is the most common malignancy among women. Triple negative breast cancers (TNBC) account for 10–20% of female breast cancer. Most TNBC cases confer poor prognosis. Brain metastasis appears in more than 15% in the triple negative breast cancer population, which causes serious decrease in survival. Changes of immunophenotype are not uncommon in breast cancer, offering new therapeutic options in cases where targetable proteins or pathways are being identified. After five lines of chemotherapy and 82 months following the first diagnosis, our patient with brain metastatic triple negative breast cancer had human epidermal growth factor receptor 2 (HER2) genetic heterogeneity in the metastatic tissue sample interpreted as HER2 status conversion. After the removal of the metastasis, we started first line therapy for metastatic HER2 positive cancer with trastuzumab and paclitaxel. After the first cycle of trastuzumab, on day 8, she had a seizure, and neurosurgical examination showed an abscess-like lesion. The punctate proved to be sterile by microbiological and pathological examination, so we continued cytostatic therapy without the anti-HER2 antibody. 3 months later, we could not identify the previous abscess-like lesion in the control computer tomography (CT) scan, and our patient had no neurological deficits. We emphasize the importance of regular tissue confirmation of predictive markers in progressive tumorous disease even if our presented case is not unequivocally a “conversion case”. Tumor subtype is determined according to algorithms and definitions published in guidelines, nevertheless, use of different guidelines may lead to controversial interpretation in cases where HER2 genetic heterogeneity is present. Furthermore, we suggest that seronegative, aseptic intracranial fluid effusion after the removal of a brain metastasis may possibly be a side effect of trastuzumab.

中文翻译：

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三阴性乳腺癌患者HER2状态转换后曲妥珠单抗治疗期间的无菌脓肿样脑病变：病例报告和文献复习。

乳腺癌是一个全球性的健康问题，它是女性中最常见的恶性肿瘤。三阴性乳腺癌（TNBC）占女性乳腺癌的10–20％。大多数TNBC病例预后不良。在三阴性乳腺癌人群中，超过15％的人出现脑转移，这会导致生存率严重下降。免疫表型的改变在乳腺癌中并不少见，在确定了可靶向蛋白质或途径的情况下提供了新的治疗选择。经过五线化疗和首次诊断后82个月，我们的脑转移性三阴性乳腺癌患者在转移组织样本中的人类表皮生长因子受体2（HER2）遗传异质性被解释为HER2状态转换。清除转移后 我们开始使用曲妥珠单抗和紫杉醇对转移性HER2阳性癌症进行一线治疗。在第一个周期的曲妥珠单抗治疗后第8天出现癫痫发作，神经外科检查发现脓肿样病变。经微生物学和病理学检查证实该点状菌是无菌的，因此我们继续使用抗HER2抗体进行细胞抑制疗法。3个月后，我们在控制计算机断层扫描（CT）扫描中无法识别出先前的脓肿样病变，而且我们的患者没有神经功能缺损。即使我们提出的病例并非明确地是“转化病例”，我们也强调在进行性肿瘤疾病中定期对预测标志物进行组织确认的重要性。肿瘤亚型是根据指南中发布的算法和定义确定的，如果存在HER2遗传异质性，则使用不同的指南可能导致有争议的解释。此外，我们建议清除脑转移后血清阴性，无菌性颅内积液可能是曲妥珠单抗的副作用。