Superficial CD34-positive fibroblastic tumor and PRDM10-rearranged soft tissue tumor are overlapping entities: a comprehensive study of 20 cases

Histopathology. 2021 Nov;79(5):810-825. doi: 10.1111/his.14429. Epub 2021 Sep 5.

Abstract

Aims: Superficial CD34-positive fibroblastic tumor (SCD34FT) and PRDM10-rearranged soft tissue tumor (PRDM10-STT) are rare mesenchymal tumors. These lesions have clinicopathological similarities, but their relationship remains controversial. This study aimed to characterise a series of cases of SCD34FT and PRDM10-STT.

Methods and results: Ten lesions each of SCD34FT and PRDM10-STT were studied using immunohistochemistry, array-comparative genomic hybridisation (aCGH), RNA sequencing and exome sequencing. Tumors mainly occurred in young adults, were generally small (< 5 cm) and arose predominantly in the superficial soft tissues of the lower extremities. Follow-up data were available in 15 cases (SCD34FT, n = 7, median 16 months; PRDM10-STT, n = 8, median 14 months), local recurrences occurred in four cases (SCD34FT, two of 10; PRDM10-STT, two of 10), while no distant spread was documented. Morphologically, tumors were relatively well-circumscribed and composed of sheets and fascicles of spindle and pleomorphic cells showing low mitotic activity (< 1/mm²) without necrosis. Other findings included: granular cell change, lipoblast-like cells, ectatic blood vessels with fibrinous material, myxoid stromal changes, metaplastic bone and increased mitotic activity (> 1/mm²). All tumors diffusely expressed CD34, while pan-keratin and desmin were commonly seen focally. SynCAM3 was diffusely expressed in 12 cases (SCD34FT, n = 5; PRDM10-STT, n = 7), independently of fusion status. aCGH profiles were 'flat' (PRDM10-STT, n = 4; SCD34FT, n = 2) and exome sequencing showed no recurrent pathogenic mutations (PRDM10-STT, n = 2; SCD34FT, n = 4). Overall, the only morphological features seen exclusively in PRDM10-STT were myxoid stromal changes (three of 10) and metaplastic bone (two of 10).

Conclusion: We expand the current knowledge on PRDM10-STT and SCD34FT and provide additional evidence for considering them as overlapping entities.

Keywords: PRDM10; RNA sequencing; comparative genomic hybridisation; sarcoma; superficial CD34-positive fibroblastic tumor.

MeSH terms

  • Adolescent
  • Adult
  • Antigens, CD34 / metabolism*
  • Biomarkers, Tumor
  • DNA-Binding Proteins* / genetics
  • DNA-Binding Proteins* / metabolism
  • Female
  • Fibroblasts / pathology*
  • Gene Rearrangement
  • Humans
  • Immunohistochemistry
  • Male
  • Middle Aged
  • Soft Tissue Neoplasms* / genetics
  • Soft Tissue Neoplasms* / metabolism
  • Soft Tissue Neoplasms* / pathology
  • Transcription Factors* / genetics
  • Transcription Factors* / metabolism
  • Young Adult

Substances

  • Antigens, CD34
  • Biomarkers, Tumor
  • DNA-Binding Proteins
  • PRDM10 protein, human
  • Transcription Factors