Case report: A mesenchymal chondrosarcoma with alternative fusions in the sella turcica.

INTRODUCTION

Mesenchymal chondrosarcoma (MCS) is a rare subtype of chondrosarcoma that occurs at widespread anatomical locations, such as bone, soft tissue, and intracranial sites. The central nervous system (CNS) is one of the most common origins of extraosseous MCS. However, alternative fusions have not been reported in this tumor.

CASE REPORT

We report a case of intracranial MCS with rearrangement. A 52-year-old woman presented with a 15-mm calcified mass around the sella turcica. She initially underwent transsphenoidal surgery for tumor resection and then additional resections for five local recurrences over 5 years. Histologically, the tumor was composed of small round to spindle-shaped cells admixed with well-differentiated hyaline cartilaginous islands. A hemangiopericytoma-like vascular pattern and small sinusoid-like vessels were also observed. RNA sequencing using RNA extracted from formalin-fixed paraffin-embedded samples from the last operation revealed two alternative variants of the fusion: (ex4):: (ex13) and (ex4)::(ex14). Both variants were confirmed as in-frame fusions using reverse transcription-polymerase chain reaction.

DISCUSSION

Cartilaginous components were often not apparent during the recurrences. In addition to the non-typical pathological finding, the correct diagnosis was hampered by the poor RNA quality of the surgical specimens and non-specific STAT6 nuclear staining.

CONCLUSION

This is the first reported case of intracranial MCS with an alternative fusion.