Clinicopathological and molecular characterisation of superficial CD34-positive fibroblastic tumour: A systematic review

Aim This systematic review aims to comprehensively evaluate the clinicopathological and molecular features of superficial CD34-positive fibroblastic tumour (SCD34FT), a recently described intermediate-grade soft-tissue neoplasm recognised in the 5th edition of the WHO classification of soft tissue tumours. Methods Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, we systematically searched for English-language studies in PubMed, Scopus, Google Scholar and Web of Science. Retrospective or original case series with ≥3 histologically confirmed cases were selected for review, whereas review articles, single case reports and conference abstracts were excluded. Risk of bias was assessed using the Joanna Briggs Institute checklist. Results A total of 190 patients across 14 selected studies met the inclusion criteria. SCD34FT mainly affected middle-aged adults, with the most common site being the lower extremity. Diffuse CD34 expression was universal across all studies. A high number of cases displayed SynCAM/CADM3 positivity, while WT1 and Pan-CK (focal) were frequent. PRDM10 fusion was detected in 73% of cases, and the most common fusions were PRDM10::MED12 (66%) and PRDM10::CITED2 (28%). Only 9/169 (5.3%) had local recurrences, whereas 4/190 (2.1%) cases had lymph node metastasis, with no distant metastasis or disease-related death. Conclusion SCD34FT is a novel entity with consistent CD34 expression and recurrent PRDM10 rearrangements and shows indolent behaviour. A high index of suspicion for SCD34FT should be warranted in a superficially located tumour with striking nuclear pleomorphism but an unexpectedly low mitotic index. Molecular studies demonstrating PRDM10 rearrangement may be helpful in atypical cases.