Shirai Yoshiki, Matsuoka Masatake, Okawa Hiroya, Miyazaki Tomohiko, Hashimoto Takayuki, Onodera Tomohiro, Hasegawa Tadashi, Matsuno Yoshihiro, Iwasaki Norimasa
Department of Orthopaedic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
Department of Surgical Pathology, Hokkaido University Hospital, Sapporo, Japan.
Int J Surg Pathol. 2025 Jul 13:10668969251357026. doi: 10.1177/10668969251357026.
The malignant transformation of schwannomas is exceptionally rare and typically results in a malignant peripheral nerve sheath tumor (MPNST). We report a unique patient with malignant transformation of a schwannoma into an S-100 negative epithelioid MPNST. A 72-year-old male patient presented with an abdominal mass, and imaging revealed a 5 cm tumor in the rectus abdominis muscle, which was diagnosed as schwannoma through biopsy. The patient opted for observation instead of surgery. Eight years later, the tumor had enlarged to 10 cm, accompanied by worsening pain. Imaging showed intra-abdominal dissemination and metastases to mediastinal and para-aortic lymph nodes. Comprehensive whole-body positron emission tomography and computed tomography imaging and meticulous re-examination of the original schwannoma biopsy definitively excluded alternative primary malignancies and established histopathological continuity between the current lesion and the pre-existing schwannoma. Immunohistochemical staining indicated the tumor was S-100 negative, SOX10 negative, H3K27me3 positive, SMARCB1/INI1 positive and EMA negative, leading to the diagnosis of S-100 negative epithelioid MPNST. Due to the rapid tumor growth, palliative radiation therapy was administered, and the patient received best supportive care. This patient was identified as an S-100 negative epithelioid MPNST.
神经鞘瘤的恶性转化极为罕见，通常会导致恶性外周神经鞘膜瘤（MPNST）。我们报告了一例独特的病例，即神经鞘瘤恶性转化为S-100阴性上皮样MPNST。一名72岁男性患者因腹部肿块就诊，影像学检查显示腹直肌有一个5厘米的肿瘤，经活检诊断为神经鞘瘤。患者选择观察而非手术。八年后，肿瘤增大至10厘米，伴有疼痛加剧。影像学检查显示腹腔内播散，并转移至纵隔和主动脉旁淋巴结。综合全身正电子发射断层扫描和计算机断层扫描成像以及对原神经鞘瘤活检标本的细致复查，明确排除了其他原发性恶性肿瘤，并确定了当前病变与既往神经鞘瘤之间的组织病理学连续性。免疫组织化学染色显示肿瘤S-100阴性、SOX10阴性、H3K27me3阳性、SMARCB1/INI1阳性、EMA阴性，从而诊断为S-100阴性上皮样MPNST。由于肿瘤生长迅速，给予了姑息性放射治疗，患者接受了最佳支持治疗。该患者被确诊为S-100阴性上皮样MPNST。
