Usefulness of 11C-methionine positron emission tomography for detecting intracranial ameloblastic carcinoma: A case report

Abstract

Ameloblastic carcinoma, secondary type, is an extremely rare odontogenic malignant tumor. The present study reports the case of a 58-year-old male with ameloblastic carcinoma that extended into the intracranial space close to the internal carotid artery. Surgical excision was performed, as headaches were being caused via compression by the mass. Small remnants of the tumor remained surrounding the internal carotid artery following surgical resection. Although the remnant tissue was not detected on magnetic resonance imaging or 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET), it was clearly visualized on ¹¹C-methionine PET in the early post-operative follow-up period. No neurological deficits were exhibited during the follow-up period, and ¹¹C-methionine PET was able to detect the remnant lesion distribution in the intracranial space. The current study presents a rare case of ameloblastic carcinoma that extended into the intracranial space. In addition, several diagnostic imaging tools were compared in order to determine the most suitable imaging modality. At present, the patient is continuing a therapeutic course of radiation and evident mass reduction has been observed. However, the therapeutic effects are currently under consideration. To the best of our knowledge, this is the first study on the effectiveness of using ¹¹C-methionine PET for detecting ameloblastic carcinoma with intracranial extension.

Keywords: ameloblastic carcinoma; intracranial extension; methionine-labeled positron emission tomography.

Figure 1

CT scan obtained on admission. (A) Axial, (C) coronal and (D) sagittal enhanced CT scans showing a mass occupying the maxillary sinus extending to the temporal base. (B) Bone imaging showing a right middle cranial base deficiency. CT, computed tomography.

Figure 2

Enhanced magnetic resonance imaging performed on admission. (A and B) Axial, (C) coronal and (D) sagittal views showing a solid mass extending from the maxillary sinus to the middle cranial base.

Figure 3

Immunohistochemical study. Hematoxylin and eosin staining results showing (A) a level of high cellularity (magnification, ×200), with (B) hyperkeratosis (magnification, ×100) and (C) necrosis (magnification, ×200). (D) MIB-1 staining (magnification, ×200). The proportion of MIB-1-positive cells was ~25%.

Figure 4

Positron emission tomography scan prior to surgery showing a high accumulation of (A) ¹¹C-methionine and (B) 5-fluorodeoxyglucose in the mass lesion.

Figure 5

Post-operative examination. (A, B) Enhanced MRI and (D) FDG-PET were unable to visualize the remnant tissue. (C) ¹¹C-methionine-PET clearly revealed the remnant tissue of the ameloblastic carcinoma around the right internal carotid artery.