Güner Güneş, Akgul Mahmut, Michal Michael, Yilmaz Asli, Bayrak Buşra Yaprak, Hasbay Bermal, Yazgan Aylin, Kandemir Nilüfer, Oktay Murat, Bayçelebi Deniz, Htoo Arkar, Lopez Jose, Hes Ondrej, Hartmann Arndt, Baydar Dilek E, Trpkov Kril, Mohanty Sambit K, Agaimy Abbas, Argani Pedram, Kösemehmetoğlu Kemal
Department of Pathology, Hacettepe University School of Medicine, Ankara, Türkiye.
Department of Pathology, Brigham and Women's Hospital, Boston, MA, USA.
Virchows Arch. 2025 Sep 18. doi: 10.1007/s00428-025-04264-6.
Solitary fibrous tumor (SFT) is a fibroblastic neoplasm characterized by prominent, staghorn, or delicate "hemangiopericytoma (HPC)-like vasculature", NAB2::STAT6 gene fusion, and its surrogate STAT6 expression. SFT may exhibit an unpredictable clinical course, necessitating risk assessment based on tumor characteristics. Renal SFTs are rare and have not been well characterized. Forty-three primary kidney SFT cases are reviewed for clinical, morphological, and immunohistochemical (STAT6, BCL2, CD34, and PAX8) features. A four-variable risk stratification by Demicco was applied based on patient age, tumor size, mitotic activity, and tumor necrosis. The mean age was 49 years (range 11-83 years) with a slight female predominance (male:female = 20:23). The mean tumor size was 7.8 cm (1.6-32 cm). Tumors were mainly located at the hilus (22/32, 68%) and had well-demarcated borders (31/42, 74%). Morphologically, tumors were categorized as 1) Fibrous ("SFT-like", 19/43, 44%), characterized by hypocellularity and prominent fine-reticular or keloidal collagen; 2) Cellular ("HPC-like", 8/43, 19%), with hypercellularity, short spindle to small cell-like proliferation, and lacking a collagenous background; 3) mixed fibrous/cellular (16/43, 37%) displaying both components. Four cases featured a lipomatous component. BCL2 was positive in all tested cases (28/28), CD34 in all but 3 cases (93%), and STAT6 in all but one case (39/40, 97.5%). PAX8 was positive in 6/34 (18%) cases. Most cases (29/43, 68%) were classified as low-risk, followed by intermediate (12/43, 27%) and high-risk (2/43, 5%) groups. Five of 29 (18%) patients had metastatic disease, and two patients with high-risk and one with intermediate-risk tumors died from the disease, while 25 patients with low- or intermediate-risk tumors were alive for an average of about 36 months. We emphasize the usefulness of the risk stratification system in predicting prognosis. PAX8 expression in a subset of renal SFT represents a potential diagnostic pitfall.
孤立性纤维瘤（SFT）是一种成纤维细胞性肿瘤，其特征为显著的鹿角状或纤细的“血管外皮细胞瘤（HPC）样脉管系统”、NAB2::STAT6基因融合及其替代标志物STAT6表达。SFT可能呈现不可预测的临床病程，因此需要根据肿瘤特征进行风险评估。肾SFT较为罕见，其特征尚未完全明确。本文回顾了43例原发性肾SFT病例的临床、形态学及免疫组化（STAT6、BCL2、CD34和PAX8）特征。基于患者年龄、肿瘤大小、有丝分裂活性和肿瘤坏死情况，应用了Demicco提出的四变量风险分层方法。患者平均年龄为49岁（范围11 - 83岁），女性略占优势（男∶女 = 20∶23）。肿瘤平均大小为7.8 cm（1.6 - 32 cm）。肿瘤主要位于肾门（22/32，68%），边界清晰（31/42，74%）。形态学上，肿瘤分为：1）纤维型（“SFT样”，19/43，44%），其特征为细胞稀少及显著的细网状或瘢痕样胶原；2）细胞型（“HPC样”，8/43，19%），细胞增多，呈短梭形至小细胞样增殖，且无胶原背景；3）纤维/细胞混合型（16/43，37%），兼具两种成分。4例有脂肪成分。所有检测病例（28/28）BCL2均为阳性，除3例（93%）外CD34均为阳性，除1例（39/40，97.5%）外STAT6均为阳性。PAX8在6/34（18%）例中呈阳性。大多数病例（29/43，68%）被归类为低风险组，其次是中风险组（12/43，27%）和高风险组（2/43，5%）。29例（18%）患者有转移，2例高风险组患者和1例中风险组患者死于该疾病，而25例低风险或中风险组患者存活，平均约36个月。我们强调风险分层系统在预测预后方面的实用性。肾SFT一部分病例中PAX8表达是一个潜在的诊断陷阱。
