Chondroid Chordoma: Is It Really a Chondrosarcoma and Does It Matter?

Background: Chondroid tumors of the head and neck continue to be a unique challenge to manage. A large subset of chondroid tumors arise in the skull base region. Most challenging of all are the chondrosarcomas and chordomas of the clivus. An entity called chondroid chordoma was first described in 1973 but has remained controversial. Immunohistochemical studies have shown that these lesions are more consistent with a low-grade chondrosarcoma. The imaging features of chordoma and chondrosarcoma overlap, but chondrosarcoma frequently has virtually pathognomonic radiographic features. However, in the clivus both entities may be particularly difficult to differentiate from one another and sometimes from other entities as well.

Objectives: The objectives of this study are to (1) determine the decree of discordance between imaging and pathology in chondroid tumors and (2) identify patients with chondroid tumors of the clivus whose radiographic features suggested chondrosarcoma but histologically were diagnosed as chordoma.

Methods: The database of the Department of Pathology and Laboratory Medicine from 1991–2011 was searched for the diagnoses of chordoma, chondrosarcoma, and chondroid chordoma of the head and neck to identify chondrosarcomas and chordomas of the clivus. The pathology reports and radiology were reviewed to identify discordance or a failure of radiology or pathology to make a definitive diagnosis. In addition, all cases diagnosed as chondroid chordoma were retrieved for further detailed evaluation.

Results: We identified 75 patients with chondroid tumors histologically diagnosed as chondrosarcoma or chordoma. To date, we have identified 26 lesions that involved the clivus for whom we have sufficient data, and virtually all of these appeared to at least theoretically have the clivus as the epicenter. Among the 26 cases, 18 had radiographic features that suggested both chondrosarcoma and chordoma within the differential diagnosis. Eleven patients had classic chordoma and nine patients had chondrosarcoma histologically, and six patients had chondroid chordoma diagnosed histologically. However, radiographic features were more consistent with chondrosarcoma in the latter group. The discordance of radiographic features in the classic chordoma and chondrosarcoma groups was rare. At least two of the patients in the chondrosarcoma group had some histological features, which resembled the chondroid chordoma group.

Conclusions: Chondroid chordoma is a rare entity, and its existence is further questioned by the fact that radiographic features of these tumors are more suggestive of chondrosarcoma. This data combined with the known calcification patterns of chondrosarcoma and the immunohistochemical profile of chondroid chordomas have prompted us to extend our study to evaluate the calcification patterns of all chondroid tumors in an ongoing subsequent study. Careful imaging evaluation is of great importance. Pathologic diagnosis of chondroid chordoma may suggest a different prognosis than classic chordoma and a tendency to be lower grade and resemble a low-grade chondrosarcoma radiographically and clinically.