Int J Gynecol Pathol. 2023 May 1;42(3):234-240. doi: 10.1097/PGP.0000000000000892. Epub 2022 Nov 3.
Synovial sarcoma (SS) is a high-grade malignant neoplasm frequently arising in the deep soft tissue of the lower and upper extremities of young adults. Primary SS in the pelvis is extremely rare with scattered case reports. It often causes a diagnostic challenge in small biopsy and/or with aberrant expression of immunohistochemical markers. Here, we report 2 unusual cases of SS in the pelvis. Microscopically both cases present with biphasic morphology including spindle and epithelioid cells. In addition, the tumor cells in both cases expressed PAX8 and estrogen receptor. PAX8 is a transcription factor usually expressed in tumors of thyroid gland, kidney, and Müllerian system origin. The expression of PAX8 especially with co-expression of estrogen receptor can be misleading and result in a diagnosis of Müllerian tumors in female patients with pelvic masses. The diagnosis of SS for both cases was confirmed either with the fluorescence in situ hybridization or reverse transcription polymerase chain reaction showing a SS18 (SYT) (18q11) gene rearrangement. It is imperative to include SS in the differential diagnosis for malignant neoplasms exhibiting monotonous spindle cells (monophasic SS) and biphasic mixed monotonous spindle and epithelioid tumor cells in female patients with a pelvic mass. Molecular study for SS18 translocation is essential for the diagnosis in such cases.
滑膜肉瘤（SS）是一种常见于年轻成人下肢和上肢深部软组织的高级别恶性肿瘤。原发性骨盆 SS 极为罕见，仅有少数病例报告。它在小活检或免疫组织化学标志物异常表达时经常会造成诊断上的挑战。在此，我们报告 2 例骨盆 SS 不典型病例。显微镜下，这两个病例均呈现双相形态，包括梭形和上皮样细胞。此外，两例肿瘤细胞均表达 PAX8 和雌激素受体。PAX8 是一种转录因子，通常在甲状腺、肾脏和 Müllerian 系统来源的肿瘤中表达。PAX8 的表达，特别是与雌激素受体的共表达，可能会产生误导，导致女性盆腔肿块患者的 Müllerian 肿瘤的诊断。通过荧光原位杂交或逆转录聚合酶链反应显示 SS18（SYT）（18q11）基因重排，两例均确诊为 SS。对于表现为单相梭形细胞（单相 SS）和双相混合单调梭形和上皮样肿瘤细胞的女性盆腔肿块恶性肿瘤，必须将 SS 纳入鉴别诊断。在这种情况下，进行 SS18 易位的分子研究对于诊断至关重要。
