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CASE 17

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A 42 year old man presented with a two- month history of severe low back pain. Clinical evaluation included normal routine roentgenograms of the lower spine. MRI studies showed a 2.3 cm lesion in the L4 vertebral body, without soft tissue extension. He had no neurological symptoms. A diagnostic needle biopsy of the lesion was performed, and he subsequently underwent resection of vertebra L4.

Post biopsy, tomography scan showed minimal sclerosis about the biopsy tract, but no lesion or evidence of bone destruction. Bone and PET scans were negative

Gross findings: On serial sagittal sectioning, a pale rather well demarcated lesion (3.2 x 2.3 x 2.2 cm ) confined to the vertebral body was identified (Image 1 ). Microscopic findings are depicted in the images 2 through 5

Image 1 : Gross photo of the lesion ( sagittal section)
Image 2 : Microscopy of the lesion at 4x
Image 3 : Microscopy of the lesion at 10x
Image 4 : Microscopy of the lesion at 20x
Image 5 : Microscopy of the lesion at 40

Send your comments to:

Sushama Patil, MD
Washington University School of Medicine
Dept. of Pathology and Immunology
Campus Box - 8118
St. Louis, MO - 63110
USA

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RESULTS

Final Diagnosis: Bone, L4 vertebra - Giant notochordal rest

Answers from Participants:

Chordoma / Vertebral Chordoma - 4 responses
Lipoma/atypical lipoma - 3 response
Fat necrosis - 1 response
Notochordal hamartoma - 1 response
Giant notochordal rest - 1 response

Other differentials considered along with some of the above stated diagnosis were liposarcoma (primary/metstatic) and chondrosarcoma.

Immunoprofile:

Vimentin - strongly positive
Cytokeratin (AE1/AE3), S - 100, epithelial membrane antigen (EMA) - Positive
Carcinoembryonic antigen (CEA), and p53 - Negative
Ki-67 ( MIB-1) - less than 5% cells show nuclear staining

Histochemical stains:

Positive staining for mucicarmine and Alcian blue with and without hyaluronidase (pH 2.5)

Microscopy: The lesion showed sheet-like proliferation of notochord-like tissue, which was composed of large cells with cleared cytoplasm. The cells were tightly compacted with well defined borders. In most of the cells the cytoplasm appeared as univacuolated space, while in others there was multivacuolation (physaliferous like). Some cells showed wisps of granular cytoplasm within an otherwise clear background. In some areas the cells fused to form a microcystic space. The nuclei were bland with even finely dispersed chromatin. Most of the cells displayed a small nucleolus. There was no evidence of nuclear atypia or mitosis ( as observed in H&E slides ). There was a conspicuous absence of bone destruction. And the demarcation between the lesion tissue and the uninvolved marrow was sharp, and the lesion had pushing borders. No mucinous matrix with cords or strands of cells was apparent. In our view, there was no evidence of a metastatic process, that may have resulted from an unknown primary.

Discussion:

We believe that this lesion represents a benign notochordal tissue and not a chordoma. Such lesions have been variously termed as Giant notochordal rest, Notochordal hamartomas or Ecchordosis physaliphora ( when present at the base of the skull ). We base this diagnosis on the following facts;

- Absence of bone destruction or soft tissue extension by radiological studies.
- The only positive finding is noted on MRI imaging ( Tomography and bone scans were negative)
- Lack of histologic evidence of lobulation, cords and strands of tumor cells in a myxoid background and most importantly lack of cellular atypia, pleomorphism or mitotic activity, as would be evident in a chordoma
- Absence of bone destruction histologically

We know of no intraosseous chordoma, which at the time of diagnosis DID NOT demonstrate either bone destruction or gross soft tissue invasion. All chordomas demonstrate radiological evidence of bone destruction either on plain roentgenograms, CT scans or MRI studies.

It should be noted however that only a handful of these "benign notochordal rest" cases have been reported (current case is our 2nd in house case ), and there are those who believe that such cases actually represent early stage chordomas. Only time and the publication of additional cases will confirm or refute these positions. As far as this case was concerned, it was our view that the prognosis in this patient was excellent, since the lesion was completely excised. It is close to two years, and this patient is alive and doing very well when he was seen at last follow up.

Reference:

- The American Journal of Surg Path 27(3); 396-406, 2003

Send your comments for this discussion to: Sushama Patil, MD