Departments of Pathology.
Urology.
Am J Surg Pathol. 2021 Feb 1;45(2):169-177. doi: 10.1097/PAS.0000000000001592.
Perivascular epithelioid cell neoplasms (PEComas) of the bladder are extremely rare, with ~30 case reports. A subset of PEComas contain TFE3 gene rearrangement, however, the distinct histomorphologic features of these translocation tumors has not been fully explored in bladder PEComas. In our series, 11 cases of bladder PEComas were collected, including 1 internal and 10 consults, with 1 case previously reported. There was a female predominance (9 female, 2 male) with a mean age of 44.2 years (24 to 61 y). In only 1 of the 10 consult cases was PEComa considered in the differential diagnosis. In 10 of 11 cases, prominent epithelioid features were noted, with the final case having focal epithelioid morphology. Mitotic rate was increased in 2 of 11 cases, and 2 of 11 cases had cytological atypia. Two cases were malignant, with invasion into perivesicle tissue in 1 case, and metastases to lungs and brain followed by death in the other case. Immunohistochemically, there was strong, and diffuse staining for cathepsin K in 10/11 cases with the 1 negative case restained on a previously stained slide. HMB-45 was diffusely positive in 8/11 cases, while melan-A was present in only 1/10 cases. Muscle markers were variably expressed with positivity for both smooth muscle actin in 6/10 cases and desmin in 3/10 cases. Keratin AE1/3 was uniformly negative (0/11). In 5/8 cases where TFE3 was rearranged by fluorescence in situ hybridization, the morphology had a predominantly epithelioid, nested architecture. Overall, bladder PEComas are particularly difficult to diagnose given their rarity, are predominantly epithelioid and do not always express melanocytic markers. Diagnosis in the bladder requires a combination of morphologic characterization, exclusion of other diagnostic possibilities, positive Cathepsin K staining, variable melanocytic marker expression, with some cases showing a TFE3 gene rearrangement.
膀胱血管周上皮样细胞瘤（PEComa）极为罕见，约有 30 例报告。PEComa 的亚组含有 TFE3 基因重排，然而，这些易位肿瘤的独特组织形态特征在膀胱 PEComa 中尚未得到充分探索。在我们的研究中，共收集了 11 例膀胱 PEComa 病例，包括 1 例原发和 10 例会诊，其中 1 例曾有报道。患者以女性为主（9 例女性，2 例男性），平均年龄为 44.2 岁（24 至 61 岁）。在 10 例会诊病例中，仅 1 例考虑到 PEComa 作为鉴别诊断。在 11 例病例中，有 10 例突出的上皮样特征，最后 1 例有局灶性上皮样形态。有 2 例病例核分裂象增多，有 2 例病例有细胞学异型性。2 例为恶性，1 例侵犯膀胱壁，另 1 例转移至肺和脑，最终死亡。免疫组化染色显示，11 例中有 10 例 cathepsin K 表达强且弥漫，未染色的 1 例病例重新染色后仍为阴性。8/11 例 HMB-45 弥漫阳性，而 10/11 例黑素瘤-A 仅 1 例阳性。肌标志物表达不同，6/10 例平滑肌肌动蛋白阳性，3/10 例结蛋白阳性。角蛋白 AE1/3 均为阴性（0/11）。在 5/8 例荧光原位杂交 TFE3 重排的病例中，形态学表现为主要为上皮样、巢状结构。总体而言，由于膀胱 PEComa 极为罕见，主要为上皮样，并不总是表达黑素细胞标志物，因此诊断特别困难。膀胱的诊断需要结合形态学特征、排除其他诊断可能性、Cathepsin K 染色阳性、黑素细胞标志物表达不同，部分病例有 TFE3 基因重排。
