Pathobiology of selected tumors of the base of the skull

Solitary lesions of the clivus: what else besides chordomas? An extensive clinical outlook on rare pathologies

BACKGROUND

Solitary non-chordomatous lesions of the clivus are rare pathologies, which represent a diagnostic challenge. This study provides an overview of the clinical, radiological and prognostic characteristics of non-chordomatous clival lesions, highlighting current therapeutic options.

METHODS

Twenty-two non-chordomatous lesions of the clivus were collected. A retrospective analysis of clinical and radiological patterns as well as survival data was conducted.

RESULTS

Clinical presentation was a result of local mass effect. Imaging features, although mainly specific, were not always diagnostic. Extent of surgery was gross total in 45.5 % of cases. Depending on the histology, biological behaviour and presence of seeding, adjuvant treatment was performed, tailoring the treatment strategy to the single patient.

CONCLUSIONS

Solitary non-chordomatous lesions of the clival bone are more prevalent than expected. They should be approached with a correct differential diagnosis, considering specific epidemiological, radiological, and histopathological characteristics, to minimise diagnostic bias and allow the planning of the best treatment strategy.

Ollier disease

BACKGROUND

Ollier disease is a rare, nonfamilial disorder characterized by multiple enchondromatosis with an asymmetric distribution and areas of dysplastic cartilage. Clinical manifestations usually start with local pain, bone swelling, and palpable bony masses, often associated with bone deformity. Intracranial enchondromas arise from the skull base because of its cartilage embryological derivation. Headache and cranial nerve palsy are the most prominent clinical findings. The only effective treatment is represented by surgery that allows to resect the tumors and to treat their complications, such as pathological fractures, growth defect, and neurological symptoms.

METHOD

We report on a 12-year-old boy affected with Ollier disease and operated on for a skull base enchondroma. The tumor was partially removed through a right pterional approach to the cavernous sinus. Serial postoperative magnetic resonance imaging showed an increasing residual tumor and the patient underwent radiation therapy.

CONCLUSION

Surgery remains the main therapy for intracranial enchondromas. Radiotherapy is required in case of sarcomatous evolution or when a gross total tumor resection is not feasible, as in the present case.

Extraosseous chordoma of the nasopharynx

BACKGROUND AND PURPOSE

Chordoma is a relatively rare tumor of the skull base and sacrum thought to originate from embryonic remnants of the notochord. Chordomas arising from the skull base/clivus are typically locally aggressive with lytic bone destruction. When chordomas occur in an extraosseous location, they may mimic other lesions of the nasopharynx. We present 5 cases of primarily extraosseous chordoma involving the nasopharynx in an effort to improve the preoperative diagnosis of this rare tumor. In addition, we review regional notochordal embryology to explain this variant tumor location.

MATERIALS AND METHODS

We reviewed the clinical and imaging data of 5 pathologically proved cases of extraosseous chordoma of the nasopharynx seen or reviewed at our institution during the last decade. All cases had both CT and MR imaging. The study had institutional review board approval.

RESULTS

The primary clinical complaint in the 5 patients with extraosseous nasopharyngeal chordoma was nasal obstruction. The extraosseous chordomas were centered in the nasopharynx. Bony lytic changes along the anterior surface of the clivus were seen on 5 of 5 CT studies. A midline sinus tract was seen in 3 of 5 patients. MR imaging showed heterogeneous hyperintense T2 signal intensity (5/5).

CONCLUSIONS

Extraosseous nasopharyngeal chordoma is a rare but important lesion to be considered in the differential diagnosis of nasopharyngeal masses. When a midline nasopharyngeal mass is found with an associated clival sinus tract, extraosseous chordoma moves to the top of the differential diagnosis list. Complete removal of the soft-tissue tumor and the clival sinus tract is the treatment of choice in such cases.

Chondrosarcomas of the skull base: review of the literature and report of two cases

Chondrosarcomas are malignant mesenchymal tumours occurring only rarely in the bones of the cranium. Less than 5% of all chondrosarcomas are located in the head and neck area and their commonest location is the ethmoids and the sphenoid sinus. They are slow-growing tumours with low malignancy rate and unclear histopathogenesis. The prevailing hypothesis is that they arise from cartilaginous remnants in the petro-clival, spheno-occipital and fronto-nasal synchondroses. Diagnosis is only made after biopsy since clinical signs and symptoms and radiological findings are not pathognomonic. Symptomatology mainly derives from tumour encroachment and infiltration of adjacent intracranial structures. Surgery is the treatment of choice, while radiotherapy has an adjunctive role. Chemotherapy is not effective. Partial tumour excision to alleviate symptoms is an acceptable surgical technique since diagnosis is usually late, but treatment can be repeated when recurrence occurs. During the last year, two cases of chondrosarcoma of the skull base were treated in our institution. Both patients were female, aged 62 and 73, respectively. Computerized Tomography and Magnetic Resonance Imaging were inconclusive and diagnosis was established after biopsy. Treatment for both cases was surgical, with partial excision due to intracranial involvement of the internal carotid artery. In one case, a temporal approach was used, whereas the other patient was operated on via a naso-orbital approach. One patient received postoperative radiotherapy. The postoperative course was uneventful in both patients and marked clinical improvement was noted 18 months and 1 year after surgery. We support the view that partial resection of chondrosarcomas of the base of the skull to alleviate symptoms is an acceptable surgical treatment.

Chordomas of the skull base: dynamic MRI

OBJECTIVE

To investigate the role of dynamic MRI in the diagnosis of chordomas at the skull base.

MATERIALS AND METHODS

Six patients with surgically proven chordomas of the skull base were examined with spin-echo technique (repetition time/echo time 200 ms/15 ms). Serial imaging was performed every 30 s for 240 s after a rapid injection of gadopenetate dimeglumine (0.1 mmol/kg). The contrast material enhancement ratio (CER) was analyzed. The CER was obtained for each region of interest as follows (Sn - So) x 100/Smax - So, where Sn indicates signal intensity at each dynamic phase; So, signal intensity on the image obtained before administration of contrast material; and Smax, maximum signal intensity of all dynamic imaging.

RESULTS

All chordomas showed very slow but steady increase of contrast enhancement with no peak within 240 s. The CERs of six cases at 30 s are 13 to 40 (mean value +/- standard deviation: 22.8 +/- 10.2).

CONCLUSION

Dynamic MRI may be helpful in differentiating between chordomas and other tumors of the skull base.