Benign Notochordal Cell Tumor (BNCT)
G. Petur Nielsen, Massachusetts General Hospital, Boston, MA
A 61 year old female developed back pain radiating into the right buttock/medial thigh after a fall. The pain persisted despite physical therapy. Imaging studies showed lesions involving thoracic and lumbar vertebrae. A biopsy of one of the lesions was performed.
Low power view of the biopsy. The marrow space is replaced by the tumor.
Sheets of large cells with abundant clear cytoplasm with round nuclei containing fine or homogeneously dense chromatin. There is no myxoid extracellular matrix.
The tumor cells are diffusely keratin positive.
Pathological/Microscopic Findings and any Immunohistochemical or Other Studies:
The biopsy shows sheets of large polyhedral cells with abundant clear to pale pink cytoplasm with
round nuclei containing fine or homogeneously dense chromatin. There is no myxoid extracellular matrix.
Immunohistochemical studies show that the tumor cells are positive for S-100, keratin and brachyury.
Chordoma. Normal fatty marrow. Hemangioma / metastatic disease (Radiographic differential
Benign notochordal cell tumor (BNCT).
Benign notochordal cell tumor (BNCT), also previously known as giant notochordal cell rest is a
distinctive slow growing notochordal cell proliferation that appears to behave in an indolent fashion.
The vast majority are asymptomatic incidental findings detected during careful dissection at autopsy or
in clinical imaging studies of the axial skeleton. At autopsy, approximately 23.5% have been found in
the clivus, 29.5% in the sacrum, 17.5% in the coccyx, 17.5% in the cervical spine and 11.5% in the lumbar
vertebra. Radiographically, they frequently manifest as an area of sclerosis in the vertebral body with
the lesion being bright on T2 weighted MRI images. Although they are usually small (<1cm,) they may a
involve substantial portion of a vertebral body, but, do not demonstrate bone destruction. They have
been identified adjacent to chordomas and they may represent a benign precursor. Morphologically, BNCT
consists of relatively well-delineated sheets of large polyhedral cells that may be focally surrounded by
or abut rebuttressed sclerotic bone trabeculae and entrap hematopoietic marrow. The cells have abundant
clear to pale pink cytoplasm and mildly pleomorphic round nuclei containing fine or homogeneously dense
chromatin. Those with clear cytoplasm resemble adipocytes. Some of the cells with pink cytoplasm
contain round hyaline globules of varying size. The globules are PAS positive diastase resistant and are
also present in small extracellular cystic spaces. No mitoses are present and there is no myxoid stroma.
Immunohistochemically, BNCT has the same profile as chordoma. The only real reliable feature that
distinguishes BNCT from chordoma aside from the clinical and radiographic findings is the lack of myxoid
matrix in BNCT.
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