Benign Notochordal Cell Tumors: A Comparative Histological Study of Benign Notochordal Cell Tumors, Classic Chordomas, and Notochordal Vestiges of Fetal Intervertebral Discs

Abstract

Intraosseous benign notochordal cell tumors are recently recognized conditions that may undergo malignant transformation to classic chordomas. This study attempts to define the morphologic and immunohistochemical characteristics of 34 benign notochordal cell tumors by contrasting them with classic chordomas and the notochordal vestiges in fetal intervertebral discs. Benign notochordal cell tumors were characterized by well-demarcated though unencapsulated sheets of adipocyte-like vacuolated and less vacuolated eosinophilic cells within axial bones. The round nuclei were mildly polymorphic but bland. The tumor cells often contained cytoplasmic eosinophilic hyaline globules and lack any intercellular myxoid matrix or necrosis. The involved bone trabeculae were often sclerotic without evidence of bone destruction. The histologic features were different from those of both notochordal vestiges in fetal intervertebral discs and classic chordomas. There was overlap in immunohistochemical reactivity of benign notochordal cell tumors and chordomas, but notochordal vestiges failed to demonstrate cytokeratin 18 positivity. A more appropriate term for the lesions is "benign notochordal cell tumor" rather than "notochordal rest" or "notochordal hamartoma" as they are not rests and do not fulfill the definition of hamartoma. Benign notochordal cell tumors do not need any surgical procedure and must be adequately recognized to prevent unnecessary operations.

Incipient chordoma: a report of two cases of early-stage chordoma arising from benign notochordal cell tumors

“…5,6 They 4 This previous case suggested a small intraosseous benign notochordal cell tumor (described as a benign notochordal lesion in the original paper) located adjacent to the coccygeal chordoma. In addition, two other small benign notochordal cell tumors were evident in the sacrum at a different level.…”

“…Benign notochordal cell tumors are usually located within bone and never infiltrate surrounding soft tissue even if they are associated with a small soft tissue mass on the periosteum. 6 It is more likely that the lesion came from the periosteum into the intervertebral disk like the incipient chordoma in case 2.…”

“…6 They are located on the periosteum just above intraosseous lesions. Their histology is identical to that of intraosseous benign notochordal cell tumors.…”

“…However, we documented a histologically confirmed case of classic chordoma arising in a precursor benign notochordal cell tumor and reported the clinicopathological details of intraosseous benign notochordal cell tumors. [4][5][6] Based on the evidence, we concluded that intraosseous benign notochordal cell tumors are benign notochordal cell lesions with potential neoplastic characteristics and possibly serve as the real precursors of classic chordomas. We recently found two interesting cases of microscopic incipient chordomas coexistent with benign notochordal cell tumors in the coccyx, which supports the above hypothesis.…”

Chondroid chordoma of the L5 spinous process and lamina: a case report

“…More recently, a distinct condition described as 'intraosseous benign notochordal cell tumors' has been recognized [18]. They have anatomical distribution identical to that of classic chordomas.…”