Proliferating tricholemmal tumors (PTTs) are rare benign neoplasms that arise from the outer sheath of a hair follicle. Occasionally, these PTTs undergo malignant transformation to become malignant proliferating tricholemmal tumors (MPTTs). Little is known about the molecular alterations, malignant progression, and management of MPTTs. Here, we describe the case of a 58-year-old female that had a widely metastatic MPTT that harbored an activating PIK3CA mutation and was sensitive to the PI3K inhibitor, alpelisib (BYL719). We review the available literature on metastatic MPTT, detail the patient’s course, and present a whole genome analysis of this rare tumor.

增殖性毛囊瘤 (PTT) 是一种罕见的良性肿瘤，起源于毛囊的外鞘。偶尔，这些 PTT 会发生恶性转化，成为恶性增殖性毛细血管瘤 (MPTT)。人们对 MPTT 的分子改变、恶性进展和管理知之甚少。在这里，我们描述了一名 58 岁女性的病例，该女性患有广泛转移性 MPTT，其具有激活的PIK3CA突变并且对 PI3K 抑制剂 alpelisib (BYL719) 敏感。我们回顾了有关转移性 MPTT 的现有文献，详细介绍了患者的病程，并提出了这种罕见肿瘤的全基因组分析。