Chondrosarcoma with Target-Like Chondrocytes: Update on Molecular Profiling and Specific Morphological Features
Abstract
This is the first histological and molecular analysis of two chondrosarcomas with target-like chondrocytes that were compared with a group of conventional chondrosarcomas and enchondromas. The unique histological feature of target-like chon-drocytes is the presence of unusual hypertrophic eo-sinophilic APAS-positive perichondrocytic rings (baskets).
In the sections stained with Safranin O/Fast green, the outer part of the ring was blue and the material in the lacunar space stained orange, simi-larly to intercellular regions. Immunohistoche mical examination showed strong positivity for vimentin, factor XIIIa, cyclin D1, osteonectin, B-cell lympho-ma 2 apoptosis regulator (Bcl-2), p53 and p16.
The S-100 protein was positive in 25 % of neoplastic cells. Antibodies against GFAP, D2-40 (podoplanin), CD99, CKAE1.3 and CD10 exhibited weak focal positivity.
Pericellular rings/baskets contained type VI collagen in their peripheral part, in contrast to the type II col-lagen in intercellular interterritorial spaces. Ultra -structural examination revealed that pericellular rings contained an intralacunar component com-posed of microfibrils with abundant admixture of aggregates of dense amorphous non-fibrillar mate-rial.
The outer extralacunar zone was made up of a layer of condensed thin collagen fibrils with admix-ture of non-fibrillar dense material. NGS sequencing identified a fusion transcript involving fibronectin 1 (FN1) and fibroblast growth factor receptor 2 (FGFR2) at the RNA level.
At the DNA level, no significant va-riant was revealed except for the presumably germ -line variant in the SPTA1 gene.