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AJNR - American Journal of Neuroradiology

A, Unenhanced axial CT scan through the nasopharyngeal region shows thickening of the nasopharyngeal tissues at the level of the left torus tubarius and fossa of Rosenmüller (arrowheads) associated with infiltration of the left parapharyngeal space (arrows).

B, Axial T2-weighted MR image through the nasopharyngeal region, obtained 1 month after A. A poorly defined mass lesion (short arrows) is visible in the left nasopharynx and parapharyngeal space. The lateral pterygoid muscle and the origin of the medial pterygoid muscle show high signal intensity, more or less isointense with fat (compare with opposite side). A region of lower signal intensity is also visible within the lesion, extending between the prevertebral muscles and the ICA (long arrow). A left-sided mastoidal effusion is also present.

C, Axial contrast-enhanced T1-weighted MR image through the nasopharyngeal region, obtained at same time as B, shows an enhancing soft-tissue mass (arrowhead) in the left nasopharyngeal and retrostyloid compartment of the parapharyngeal space, extending around the left ICA (small white arrow) into the skull base (region of hypoglossal canal, long white arrow), and into the prevertebral muscles (small black arrows). The anterocranial part of the pterygoid muscles also shows some enhancement (large black arrow).

D, Coronal contrast-enhanced T1-weighted image, obtained 4 months after B and C, shows further progression of the lesion, now extending up to the foramen ovale with associated enhancement on the floor of the middle cranial fossa (arrow).

E and F, Axial T2-weighted (E) and contrast-enhanced T1-weighted (F) images, obtained 4 months after D, after a course of corticosteroids, show the mass lesion is clearly reduced in size. In E, low signal intensity is seen in the left parapharyngeal space, in the fat plane between the lateral pterygoid and temporalis muscle, and around the ICA (arrow). In F, enhancement is visible in and around the left lateral pterygoid muscle and around the left ICA; the normal signal void is not seen in this artery (arrow).

G and H, Axial unenhanced (G) and contrast-enhanced fat-suppressed (H) T1-weighted images, obtained 5 months after E and F, when symptoms recurred. The lesion now extends into the left retromaxillary fat and pterygopalatine fossa (arrows, G) and into the orbital apex. Soft-tissue enhancement can be seen posterolaterally in the left orbit (long arrow, H). Absence of normal signal void is evident in the left ICA in the horizontal part of the left carotid canal (arrowhead, G) and in the left cavernous sinus.

A, Coronal unenhanced T1-weighted image through the base of the skull. The left pterygopalatine fossa appears infiltrated by soft tissue (thick arrow), isointense with muscle, extending into the inferior orbital fissure (thin arrow). On the opposite side, the pterygopalatine fossa displays its normal high T1 signal intensity, with the internal maxillary artery (arrowhead) visible as a signal void.

B and C, Sagittal contrast-enhanced T1-weighted images through the left pterygopalatine fossa: C is 4 mm medial to B. The enhancing mass lesion (arrows, B) is seen to grow through the inferior orbital fissure (white arrow, C) in the orbital apex and into the superior orbital fissure (black arrow, C).

A–C, Axial contrast-enhanced CT scans show an enhancing soft-tissue mass (arrows, A) lying against the enlarged and enhancing right submandibular salivary gland (star). At a higher level (B), the mass (arrows) cannot be distinguished from this gland. In C, the soft-tissue mass extends into the medial pterygoid muscle (arrows), abutting the right oropharyngeal wall; there is infiltration of the fat in the mandibular foramen (arrowhead) and associated sclerosis of the mandibular ramus, which appears slightly deformed.

D, Axial T2-weighted MR image shows a poorly defined soft-tissue structure, more or less isointense with fat, in the right masticator space.

E, Unenhanced T1-weighted image shows that the mass is largely isointense with muscle, with some small low-intensity areas (arrows); some signal loss is evident in the right mandibular ramus.

F, After injection of contrast material, there is clear enhancement within the mass, except for the previously indicated low-signal areas, which possibly correspond to areas of fibrosis.

G, Coronal T1-weighted image shows the mass infiltrating the medial pterygoid muscle up to its attachment at the skull base (arrows); the submandibular salivary gland is displaced inferiorly (star).

H, Low-power histologic section shows spindle cells embedded in a collagenous background and intermingled with mononuclear inflammatory cells (H and E, original magnification x125).

I, At high power, the admixture of the inflammatory cells and the plump (myo)fibroblastlike cells is seen to a better extent (H and E, original magnification x325).