软骨母细胞瘤是一种罕见的良性软骨肿瘤，主要局限于骺和骨突。骺外区域的病例非常少见。骨膜外的软骨母细胞瘤极为罕见；据我们所知，文献中只报道了两例被认定为“骨膜外软骨母细胞瘤”的病例。我们报告了两例位于股骨颈下表面的干骺骨膜外软骨母细胞瘤。两例均为少细胞型，伴有异常的致密硬化反应。通过肿瘤细胞中表达的组蛋白3.3和K36M突变体的检测，支持了软骨母细胞瘤的诊断。© 2023. 作者，由国际骨科协会（ISS）独家授权。

Chondroblastoma is a rare benign cartilaginous tumor mostly confined to the epiphyses and apophyses. Cases outside the epiphyseal region are exceedingly rare. Extramedullary chondroblastomas are exceptional; to our knowledge, only two cases qualified as "periosteal chondroblastoma" have been described in the literature. We report two cases of metaphyseal periosteal chondroblastoma both located on the inferior surface of the femoral neck. Both cases were paucicellular with an unusual dense sclerotic reaction. The diagnosis of chondroblastoma was supported by the expression of histone 3.3, K36M mutant in tumor cells.© 2023. The Author(s), under exclusive licence to International Skeletal Society (ISS).