10年の経過で増大した肺原発benign notochordal cell tumor（BNCT）の1例

A case of primary pulmonary benign notochordal cell tumor（BNCT）with slow growth over a 10-year period

benign notochordal cell tumor（BNCT）は，脊索への分化を示す良性腫瘍であり，多くは脊椎や斜台の骨内に偶発的に発見される。骨外性の発生は極めてまれであり，肺原発の症例が少数例報告されているのみである。今回我々は，10年という長期の画像経過で緩徐な増大を認めた肺原発BNCTの1例を経験した。このことから，胸膜直下の境界明瞭な円形の充実性結節で，ごく緩徐な増大を呈する病変の鑑別に肺原発BNCTも考慮されるものと思われる。

Benign notochordal cell tumor（BNCT）is a lesion with notochordal differentiation that almost exclusively arises in the axial skeleton, and primary pulmonary involvement is exceptionally rare. We present a rare case of primary pulmonary BNCT with radiologically confirmed slow growth over a 10-year period. A woman in her 60s was incidentally found to have a 5-mm, well-defined subpleural nodule in the left lung on chest CT. Review of CT scans obtained 10 years earlier revealed gradual enlargement of the lesion. Wedge resection was performed to exclude malignancy. Histopathologic examination showed vacuolated cells in a myxoid stroma without cytologic atypia, and immunohistochemistry was positive for brachyury. Systemic imaging revealed no evidence of a primary chordoma, leading to a final diagnosis of primary pulmonary BNCT. Although exceedingly rare, primary pulmonary BNCT should be considered in the differential diagnosis of a slowly enlarging subpleural nodule.