Applied Radiology

Diagnosis

Chordoma

Findings

The radiograph (Figure 1) showed a lytic expansile lesion of the sacrum. Bone and soft tissue windows from CT imaging confirmed the lytic expansile lesion of the sacrum with amorphous intralesional calcification (Figures 2 and 3).

PATHOLOGY FINDINGS

Percutaneous biopsy revealed a diagnosis of chordoma. Final pathologic examination confirmed the needle-biopsy diagnosis.

Discussion

Chordomas are rare malignant neoplasms that arise from remnants of the embryological notochord. The incidence of chordomas is approximately 1 per 2 million. The major site for chordomas is the sacrococcygeal region, which accounts for 50% of all chordomas. Other sites include the skull base (35%) and cervical, thoracic, or lumbar vertebral bodies (15%).¹ Chordomas occur more frequently in males and usually present in the sixth decade of life.²

Sacral chordomas are locally invasive, slow-growing neoplasms with a poor long-term prognosis. Common presenting symptoms include pain and weakness in the lower limb/hip as a result of sacral nerve root compression and autonomic dysfunction (urinary/rectal incontinence or sexual dysfunction).² At the initial physical examination, the only abnormality may be a palpable mass found on a digital rectal examination. These clinical symptoms, combined with a high index of suspicion, can be confirmed by imaging and histopatho- logical studies.

The differential diagnosis includes primary neural tumors (schwannoma, neurofibroma, meningioma, ependymoma), primary osseous tumors (giant cell tumor, chordoma, aneurysmal bone cyst, osteoblastoma, lymphoma, and chondrosarcoma), metastases, and myeloma. However, intralesional calcifications are much more suggestive of chordoma.

The poor prognosis of sacral chordomas results from their insidious onset and nonspecific clinical presentation. Consequently, chordomas are often not diagnosed until there is local invasion with involvement of the surrounding neurological structures. Chordomas do not have a propensity for distant metastases.¹ The differential diagnosis of sacral chordoma includes soft tissue neoplasms (ie, osteosarcoma) that involve expansile masses in the pelvis, chondroid chordoma, and, in males, prostatic carcinoma.

The radiologic work-up for sacral chordoma includes radiography, CT, and magnetic resonance (MR) imaging. Radiographic findings include a sacral soft tissue mass, local bony destruction, and enlarged neural foraminae. These findings are nonspecific and generally do not aid significantly in diagnosis.³ CT will confirm and will more clearly display the radiographic findings of central calcification of the mass and cystic spaces.⁴ MR imaging has become an invaluable tool and is superior to radiography and CT in the pre- and postoperative evaluation of sacral chordomas, as it can show tumor extension to the sacroiliac joints and also to the gluteal and spinal muscles to better advantage. Sagittal images have proven to be the most effective in determining tumor extent. Sacrococcygeal chordomas typically have low signal intensity on T1-weighted images and high signal intensity on T2-weighted images and exhibit heterogeneous enhancement following administration of gadolinium.⁵

Once the sacral mass is discovered, fine-needle aspiration biopsy is the next most appropriate step.⁶ The diagnosis of chordoma can be confirmed by the presence of physaliferous cells in a lobular arrangement. Physaliferous cells exhibit a multivacuolated cytoplasm with a "bubblelike" appearance and are positive on periodic-acid Schiff (PAS) staining. The typical chordoma contains these cells, while a chondroid chordoma has areas of cartilaginous tissue. The gross appearance of chordoma is an expansile soft-tissue mass with a lobualted appearance and cystic spaces filled with gelatinous material.⁷

Local surgical resection is the gold standard of treatment for sacral chordomas. The 2 most commonly used techniques are radical resection and subtotal excision. Preoperative imaging is imperative in determining which therapeutic technique should be employed. Patients who undergo radical resection generally experience longer disease-free intervals compared with patients who undergo subtotal excision (2 years versus 8 months, respectively). However, studies have shown an increased rate of surgery-associated neurologic deficits related to radical resection when compared with subtotal excision. Sacral chordomas have a high rate of local recurrence (~70%), with most patients requiring more than 1 surgery. The mean cumulative survival period is approximately 7 years.²

CONCLUSION

This case represents a typical example of sacral chordoma. The lytic expansile sacral mass with amorphous calcifications is typical of this diagnosis. Percutaneous biopsy of this lesion should reveal the typical physaliferous cells with PAS-positive staining. The treatment is surgical excision.

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