Intraosseous Benign Notochord Cell Tumors (BNCT): Further Evidence Supporting a Relationship to Chordoma

Abstract

Previous studies have documented the existence of intraosseous benign notochordal cell tumors (BNCTs) within the axial skeleton. Evidence suggests that they may be associated with the development of chordomas. To further investigate the relationship between BNCT and classic chordoma, we reviewed a large series of resected sacral/coccygeal chordomas in an attempt to identify the presence of coexisting BNCTs. Eighty-two sacrectomy/coccygectomy specimens performed for chordoma were identified. Available hematoxylin and eosin slides were reviewed to identify BNCTs and assess their relationship with the coexisting chordoma. BNCTs were defined, in accordance with prior descriptions, as cohesive aggregates of large cells that appeared adipocyte-like because of their vacuolated cytoplasm. The cells exhibited only minimal nuclear atypia and lacked lobulation and myxoid stroma. We identified 6 BNCTs, each was adjacent to but separate from the sacral chordoma. There were 5 females and 1 male, and the mean age was 58 years. Five lesions arose in the sacrum. One lesion arose in the coccyx, and involved 2 contiguous vertebral levels. The BNCTs ranged in size from 1 to 20 mm with a mean size of 6.1 mm. The lesions were exclusively composed of adipocyte-like nuclei without significant nuclear atypia or myxoid stroma. Three lesions contained sclerotic bony trabeculae and intralesional hematopoietic elements were identified in 1 case. In all cases the chordoma was of the conventional type and were morphologically different from the BNCT. BNCTs were identified in 7.3% of sacral/coccygeal resections performed for primary chordoma. We speculate that this finding provides further evidence that BNCT is the precursor lesion for chordoma. Additional investigations are needed to further understand this relationship.