Q1: Describe the radiographic and MRI findings

The anteroposterior radiograph of lumbosacral spine reveals a lytic lesion of the sacrum involving the S2–4 vertebra. MRI reveals a destructive mass lesion involving the S2–4 vertebra. The mass is involving the sacral canal displacing the sacral nerve roots at these levels. Associated pelvic component of the mass is predominantly seen at the S4 level. The rectum and the bladder appear to be free in the MRI scan.

Q2: What is the most likely diagnosis?

The most likely diagnosis is sacral chordoma. The MRI findings plus the age of the patient and the classical findings of low back pain with constipation, urinary hesitancy, and a sacral mass makes sacral chordoma the diagnosis.

Q3: What is its management?

The primary curative treatment of sacral chordoma is surgery. Total surgical extirpation offers the best chance for cure. When radical excision cannot be achieved, adjuvant therapy plays an important part. Radiotherapy has been used in chordomas for palliation and for radical treatment in patients with residual disease after partial resection.

Discussion

Chordoma is a rare tumour arising from the primitive notochord located along the axial skeleton.¹ More than half of these tumours arise in the sacral region, 30%–40% from the clivus, and the rest (about 15%) arise elsewhere in the axial skeleton.² Chordoma is the most frequent primary malignant tumour of the sacrococcygeal region. The average age of onset is in late adulthood with males being affected two to three times more frequently than females. Due to their insidious onset and vague clinical symptoms, the time lapse between the onset of symptoms and diagnosis is more than a year. Since the visceral and vital neurological structures lie in vicinity, the ideal treatment of wide excision is difficult. Sacral chordomas are slow growing, locally aggressive tumours with a high recurrence rates.³

The earliest and the most common symptom of the sacral chordomas is sacral pain (box 1). Initially, the pain may be discontinuous and not well localised. With the invasion of sacrum and the nerve roots, it becomes intractable and localised to the anal region. The nerve root compression suggests tumour invasion into the foramina producing symptoms such as urinary complaints, constipation, and radicular leg pain. These complaints may lead to a false diagnosis of haemorrhoids, pilonidal sinus, or prolapsed intervertebral disc.⁴ Urine or faecal incontinence, intestinal obstruction, bleeding from the rectum and bladder are seen when the disease has spread extensively.⁵

On physical examination, the tumour is usually felt between the rectum and sacrum. At rectoscopy, the rectal mucosa is found to be normal and intact. In general, sacral chordomas may spread to regional lymph nodes but visceral organ metastasis is rarely seen. Bone destruction is the most prominent finding in sacral chordomas. Radiologically, they may be confused with chondroma, chondrosarcomas, and giant cell tumour.⁴ All other presacral tumours should also be included in the differential diagnosis (box 2).

As a rule, chordoma should be diagnosed histologically. A biopsy or fine needle aspiration cytology (FNAC) should be performed only via a posterior route. A transrectal biopsy should not be done as it may lead to rectal seeding of the tumour.⁶ Microscopically, it consists of pleomorphic cells arranged in clusters amid myxoid matrix. Spindle shaped cells are also seen. These cells show vacuolated cytoplasm with prominent vesicular nuclei.

The modern imaging techniques of computed tomography and MRI have helped in the earlier diagnosis and better delineation of the extent of the tumour. A chordoma contrasts highly with the adjacent soft tissue in T2 weighted images. MRI helps in better surgical planning, leading to less radical surgery, decreased morbidity, and better long term outcome. It is also useful for evaluation of recurrence in follow up.

A radical excision is the treatment of choice for sacral chordomas. The average survival from the onset of symptoms for sacral chordomas is usually 6.4 years.⁷ Bladder and rectal functions after surgery are major problems. If bilateral sacral nerve roots are sectioned, normal urogenital and rectal functions are lost. However, it is imperative that surgical margins should not be compromised, as the next surgery after local relapse becomes very difficult and will involve the resection of many more nerve roots. Since radical surgery is feasible only in a few cases, radiotherapy plays an important part. It has been attempted in cases for palliation and for radical treatment in patients with residual disease after subtotal or partial resection. Postoperative irradiation for local recurrence helps improve the quality of life, as it effectively relieves pain.⁸ Recent advances in radiation therapy like particle therapy (proton beam) offer great potential for treating residual disease with minimum normal tissue toxicity.

The prognosis of patients with sacral chordoma is reported to be dismal and attributable to the usual intralesional surgery performed (box 3). It is imperative that even the biopsy or FNAC be performed in referral tumour centres to reduce the risk of local recurrence, metastasis, and decreased survival.⁹

In conclusion, effective management of sacral chordoma involves early diagnosis, adequate surgical resection with tumour-free margins, followed by high dose radiotherapy and close follow up.

Final diagnosis

Sacral chordoma.