A re-evaluation of imaging criteria to assess aggressive masticator space tumors

To evaluate the correlation between the gross imaging evidence of an aggressive masticator space (MS) tumor and the presence of such a MS malignancy.

Thirty patients were identified retrospectively who had a malignancy that either arose in or metastasized to the MS, had pathologic verification of the diagnosis, and had magnetic resonance (MR) and/or computed tomographic (CT) images. Specifically evaluated was the presence or absence of gross imaging evidence of mandibular erosion and the integrity of the medial MS fascia as evaluated by a smooth margin between this fascia and the parapharyngeal space fat.

Of the 30 tumors, 28 were high-grade malignancies and 2 were histiocytoses. Of these, 5 had mandibular erosion and violation of the MS fascia, 19 had bone erosion with an intact fascia, 4 had neither bone erosion nor fascial violation (3 of these patients were under the age of 20 years), and 2 had fascial violation with no bone erosion.

In 76.7% of patients with a malignancy arising in the MS, on imaging the medial MS fascia was grossly intact. There were 4 patients with MS malignancy and neither violation of the medial MS fascia nor mandibular bone erosion. Thus, these imaging findings may not be good criteria to evaluate the presence of a high-grade MS malignancy, especially if the patient is under the age of 20 years, in which age group MS sarcomas are more likely to arise.