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Pulmonary Tumor With Notochordal Differentiation:Report of 2 Cases Suggestive of Benign Notochordal
Cell Tumor of Extraosseous Origin (Am J Surg Pathol 2011;35:1158–1164)
Abstract: Intraosseous benign notochordal cell tumor (BNCT) is
a lesion postulated to be of notochordal cell origin. BNCT has
recently been recognized as a potential precursor of classic
chordoma, a rare malignant neoplasm usually presenting in the
sacrococcygeal region, skull base, or mobile spine. Extra-axial
chordoma is extremely rare, and only 2 cases of pulmonary
chordoma have been reported previously. We describe herein 2
cases of hitherto-unreported lung tumors that were diagnosed as
BNCT. The patients were a middle-aged asymptomatic man and
woman who were each incidentally found to have a 15-mm
pulmonary nodule on computed tomography. They underwent
surgical resection of the tumors under a diagnosis of probable
benign tumor of uncertain nature. Histopathologically, both
tumors showed solid sheets of peculiar adipocyte-like univacuo-
lated cells, multivacuolated cells, and less vacuolated cells with
small, round nuclei and mildly eosinophilic cytoplasm. Mitosis
was absent. These features were typical of BNCT. Immunohis-
tochemically, the tumor cells in both cases were positive for
brachyury, a transcription factor essential for notochordal cell
differentiation and for other markers of notochordal cells
including cytokeratins, vimentin, and S-100 protein. Postopera-
tively, extensive radiographic examination of the whole body
revealed no evidence of a primary tumor elsewhere, and both
patients are alive and well, with no evidence of disease 1 year
after surgery. These 2 cases raise the possibility of a new
explanation for the histogenesis of extra-axial chordomas:
BNCT may be a precursor lesion of not only conventional axial
chordoma but also of extra-axial chordoma.
Key Words: benign notochordal cell tumor, chordoma, lung,