Department of Dermatology, West Virginia University, Morgantown, WV; and.
Department of Pathology, Anatomy, and Laboratory Medicine, West Virginia University, Morgantown, WV.
Am J Dermatopathol. 2020 Jun;42(6):e72-e75. doi: 10.1097/DAD.0000000000001611.
Primary osteoma cutis is a rare condition belonging to a spectrum of related genetic disorders, including progressive osseous heteroplasia, plate-like osteoma cutis, and Albright hereditary osteodystrophy, which share identical histologies with cutaneous intramembranous ossification and mutations in GNAS. We report a case of a 15-week-old girl who presented with an enlarging, indurated subcutaneous lesion on her right flank. CT scan showed an extensive subcutaneous sheet of calcification. Histologic evaluation revealed heterotopic calcification and intramembranous ossification within the dermis and mature bone largely replacing the subcutaneous fat compatible with osteoma cutis. Molecular testing was performed and identified an inactivating GNAS mutation. Unique to this case is a dermal proliferation of bland spindle cells that blended with deposited osteoid material. This has not been reported in association with primary osteoma cutis previously. These spindle cells were positive for CD44, Bcl-2, muscle-specific actin, and smooth muscle actin while negative for CD34. We hypothesize that these cells are immature mesenchymal cells, representing an early cellular phase of ossification. We favor these cells provide the background in which ossification is occurring, supporting the theory of osteoblastic metaplasia in the etiology of this condition.
原发性皮肤骨瘤是一种罕见的疾病，属于一系列相关的遗传疾病，包括进行性骨异质增生、板状皮肤骨瘤和 Albright 遗传性骨营养不良症，它们与皮肤内骨化和 GNAS 突变具有相同的组织学特征。我们报告了一例 15 周大的女孩，其右侧腰部出现一个不断增大的硬结皮下病变。CT 扫描显示广泛的皮下片状钙化。组织学评估显示真皮内异位钙化和骨化，成熟骨大量替代皮下脂肪，符合皮肤骨瘤。进行了分子检测，发现了一个失活的 GNAS 突变。这个病例的独特之处在于真皮内有温和的梭形细胞增生，与沉积的类骨质材料混合。以前在原发性皮肤骨瘤中没有报道过这种情况。这些梭形细胞对 CD44、Bcl-2、肌特异性肌动蛋白和平滑肌肌动蛋白呈阳性，而对 CD34 呈阴性。我们假设这些细胞是未成熟的间充质细胞，代表骨化的早期细胞阶段。我们倾向于这些细胞提供了正在发生骨化的背景，支持了该病症病因中骨母细胞化生的理论。
