PRDM10-rearranged Soft Tissue Tumor: A Clinicopathologic Study of 9 Cases

Am J Surg Pathol. 2019 Apr;43(4):504-513. doi: 10.1097/PAS.0000000000001207.

Abstract

Gene fusion transcripts containing PRDM10 were recently identified in low-grade undifferentiated pleomorphic sarcomas (UPS). Here, we describe the morphologic and clinical features of 9 such tumors from 5 men and 4 women (age: 20 to 61 y). Three cases had previously been diagnosed as UPS, 3 as superficial CD34-positive fibroblastic tumor (SCD34FT), 2 as pleomorphic liposarcoma, and 1 as pleomorphic hyalinizing angiectatic tumor. The tumors were located in the superficial and deep soft tissues of the thigh/knee region (4 cases), shoulder (2 cases), foot, trunk, and perineum (1 case each) ranging in size from 1 to 6 cm. All showed poorly defined cellular fascicles of pleomorphic cells within a fibrous stroma with frequent myxoid change and a prominent inflammatory infiltrate. All displayed highly pleomorphic nuclear features, but a low mitotic count. Most tumors were well circumscribed. One of 9 tumors recurred locally, but none metastasized. Immunohistochemically, all were CD34 and showed nuclear positivity for PRDM10; focal positivity for cytokeratins was seen in 5/6 cases. PRDM10 immunoreactivity was evaluated in 50 soft tissue tumors that could mimic PRDM10-rearranged tumors, including 4 cases exhibiting histologic features within the spectrum of SCD34FT. Except for 2/6 pleomorphic liposarcomas and 1/4 myxofibrosarcomas, other tumors did not show nuclear positivity but displayed weak to moderate cytoplasmic immunoreactivity. In conclusion, PRDM10-rearranged soft tissue tumor is characterized by pleomorphic morphology and a low mitotic count. Its morphologic spectrum overlaps with SCD34FT. Clinical features of this small series suggest an indolent behavior, justifying its distinction from UPS and other sarcomas.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • DNA-Binding Proteins / genetics*
  • Female
  • Gene Rearrangement
  • Humans
  • Male
  • Middle Aged
  • Sarcoma / classification
  • Sarcoma / genetics*
  • Sarcoma / pathology*
  • Soft Tissue Neoplasms / classification
  • Soft Tissue Neoplasms / genetics*
  • Soft Tissue Neoplasms / pathology*
  • Transcription Factors / genetics*
  • Young Adult

Substances

  • DNA-Binding Proteins
  • PRDM10 protein, human
  • Transcription Factors