Superficial CD34-positive fibroblastic tumor (SCD34FT) is a rare soft tissue neoplasm that shows overlapping features with PRDM10-rearranged soft tissue tumor (PRDM10-STT). This study characterizes the clinicopathologic, immunohistochemical, and molecular features of SCD34FT in a series of 59 cases. Fluorescence in situ hybridization to assess for PRDM10 rearrangement was performed in 12 tumors. Immunohistochemistry for CADM3 and WT1 was performed; CADM3 was also assessed in histologic mimics. Our cohort of 33 male and 26 female had a median age of 42 (range: 14 to 85) years. Tumors were most commonly located in the lower limb (73%), upper limb (8%), back (7%), and supraclavicular region (3%). The median tumor size was 3.0 cm (range: 1.0 to 9.0 cm). Clinical follow-up in 32 patients (median duration: 26 mo) revealed 2 local recurrences (6%). One patient developed regional lymph node metastases which were completely excised. Microscopically, SCD34FT comprised spindled and pleomorphic cells with glassy cytoplasm and occasional granular cell change. Fluorescence in situ hybridization confirmed PRDM10 rearrangement in 3/8 cases (38%). SCD34FT frequently expressed CADM3 (95%) and WT1 (75%). CADM3 was less diffusely positive in pleomorphic hyalinizing angiectatic tumor (40%), pleomorphic liposarcoma (20%), and undifferentiated pleomorphic sarcoma (10%). We corroborate that SCD34FT is indolent but may rarely metastasize to lymph nodes without adverse outcomes. CADM3 and WT1 may be useful in the distinction from histologic mimics. Since cases of SCD34FT with and without demonstrable PRDM10 rearrangement were clinicopathologically indistinguishable, our study further supports that SCD34FT and PRDM10-STT likely constitute a single entity.

浅表 CD34 阳性成纤维细胞瘤 (SCD34FT) 是一种罕见的软组织肿瘤，与PRDM10重排软组织肿瘤 ( PRDM10 -STT) 有重叠特征。本研究在一系列 59 例病例中描述了 SCD34FT 的临床病理学、免疫组织化学和分子特征。在 12 个肿瘤中进行荧光原位杂交以评估PRDM10重排。进行了CADM3和 WT1 的免疫组织化学；CADM3在组织学模拟中也进行了评估。我们的队列由 33 名男性和 26 名女性组成，中位年龄为 42 岁（范围：14 至 85 岁）。肿瘤最常见于下肢（73%）、上肢（8%）、背部（7%）和锁骨上区域（3%）。中位肿瘤大小为 3.0 cm（范围：1.0 至 9.0 cm）。32 例患者（中位持续时间：26 个月）的临床随访显示 2 例局部复发（6%）。一名患者出现区域淋巴结转移，完全切除。显微镜下，SCD34FT 由梭形和多形细胞组成，细胞质呈玻璃状，偶尔有颗粒细胞变化。荧光原位杂交证实了 3/8 例（38%）的PRDM10重排。SCD34FT 经常表达CADM3 (95%) 和 WT1 (75%)。CADM3在多形性玻璃样血管扩张性肿瘤 (40%)、多形性脂肪肉瘤 (20%) 和未分化多形性肉瘤 (10%) 中弥漫阳性较少。我们证实 SCD34FT 是惰性的，但可能很少转移到淋巴结而没有不良后果。CADM3和 WT1 可能有助于区分组织学模拟物。由于具有和不具有明显PRDM10重排的 SCD34FT 病例在临床病理学上无法区分，我们的研究进一步支持 SCD34FT 和PRDM10 -STT 可能构成一个单一实体。