A large invasive chondroblastoma on the temporomandibular joint and external auditory canal: a case report and literature review

Abstract

Background: Chondroblastomas, which account for approximately 1% of all bone tumors, typically occur in long bones, such as the femur, humerus, and tibia. However, in extremely rare cases, they may also occur in the craniofacial region where the tumor is often found in the squamous portion of the temporomandibular joint (TMJ) and in the temporal bone.

Case presentation: This case report describes a large chondroblastoma (diameter, approximately 37 mm) that occurred in the TMJ. The tumor was sufficiently aggressive to destroy the TMJ, mandibular condyle neck, external auditory canal (EAC), mandibular fossa of the temporal bone, and facial nerve. The tumor was completely excised using a pre-auricular approach. The EAC and surgical defect were successfully reconstructed using a temporoparietal fascia flap (TPFF) and an inguinal free fat graft. There was no local tumor recurrence at the 18-month follow-up visits. However, the patient developed sensory neural hearing loss, and his eyebrow paralysis worsened, eventually requiring plastic surgery.

Conclusion: Large, invasive chondroblastomas of the TMJ can be completely removed through a pre-auricular approach, and the resulting surgical defect can be reconstructed using TPFF and free fat grafts. However, preoperative evaluation of the facial nerve and auditory function is necessary. Therefore, a multidisciplinary approach is essential.

Keywords: Chondroblastoma; Inguinal fat graft; Multidisciplinary approach; Pre-auricular approach; Temporomandibular joint; Temporoparietal fascia flap.

Fig. 1

Preoperative computed tomography A coronal view shows erosion of the skull base temporal bone and the moth-eaten appearance of the right mandible neck. The mild thickening of the tympanic membrane (B, arrow) and fluid collection in the external auditory canal (C, arrow) were tentatively diagnosed as external otitis due to an error in the interpretation of the images. Preoperative magnetic resonance imaging D coronal view shows an inhomogeneous, multi-lobulated mass with an intermediate signal

Fig. 2

A The pre-auricular approach, using a hockey-stick incision, is shown. The incision extends anterosuperiorly. B The completely dissected and removed tumor is shown. The largest tumor dimension is 37 mm. C The temporal fascia flap is harvested. D A defect in the anterior wall of the external auditory canal is covered using a temporal fascia flap (arrow). E An inguinal free fat graft is shown. F The inguinal fat graft is covered by a pedicled temporoparietal fascia flap (TPFF)

Fig. 3

A The tumor is composed of sheets of mononuclear cells (below the line) admixed with occasional multinuclear cells (arrow); hematoxylin and eosin stain, 200×. The eosinophilic and basophilic chondroid matrix (above the line) is intermingled. B The degenerative area shows perinuclear lace-like calcification (hematoxylin and eosin stain, 400×)

Fig. 4

Magnetic resonance imaging (A) coronal scan, 7 months postoperatively, shows the stable inguinal fat pad graft covering the temporal bone defect (arrow) and do not indicate chondroblastoma recurrence. At the 18-month follow-up visit, the magnetic resonance imaging (B) coronal view fails to reveal newly developed, abnormally enhanced lesions or restricted diffusion into the operation bed (arrow). There is no evidence of local recurrence