Intracranial chondroma of the falx in a child; Case report & review of the literature

Intracranial chondromas (ICC) comprise 0.2 – 0.3% of intracranial tumours. They are usually located at the skull base and thought to arise from foci of synchondrosis. Extra‐skeletal ICC are less common; only 50 cases have been reported. These tumors have no bone attachment and their histogenesis isn't known. We present the immunohistochemical (IHC) and electron microscopy (EM) characteristics of a falx chondroma in a 15 year old child. The tumor was lobulated, 3.5 × 3.0 × 3.0 cm in diameter, pearly‐white externally and gray, with multiple gelatinous islands and small foci of ossification on the cut surface. The paraffin embedded tissue was used for routine and IHC stains. EM was performed on glutaraldehyde fixed material. Microscopic examination revealed a well differentiated chondroma with foci of ossification and islands of vacuolated cells (VC) encircling thin‐walled capillaries. The majority of VC was represented by PAS, Oil‐red‐O, Vimentin (VIM), CD68, CD31, trypsin‐anti‐chymotrypsin (TACT) and ferritin‐ positive macrophages. A subpopulation of spindle VC displayed reaction for S100, ferritin, TACT and VIM and on EM showed transitional morphological features suggestive of transformation to chondrocytes. There was no evidence of transitional forms to arachnoid cell. In conclusion, our IHC and EM studies suggest origin of extra‐skeletal ICC from a perivascular multipotential mesenchymal cell.