Ancient schwannoma in the parotid gland: A case report and review of the literature

Abstract

Schwannomas are uncommon neoplasms of neurologic origin that are rare in the salivary glands. A schwannoma that persists for a long time is referred to as an ancient schwannoma if it is accompanied by degenerative changes on histology. The case described herein involved a 37-year-old man with an ancient schwannoma that had persisted for 20 years in his right parotid gland. Clinically, the lesion presented with swelling and pain. Computed tomography revealed a well-defined, multilocular enhanced lesion. T2-weighted magnetic resonance images displayed multilocular hyperintensity, while T1-weighted images showed a high signal at the lobulated margin and a homogeneous low signal internally. The preoperative diagnosis, based on the lesion's location and imaging diagnosis, was Warthin's tumor. However, a biopsy conducted after surgical excision identified the lesion as a schwannoma with cystic degeneration. This report also presents a summary of the characteristics of rare cases of schwannoma in the major salivary gland based on this case and a literature review.

Keywords: Magnetic Resonance Imaging; Neurilemmoma; Parotid Gland; Tomography, X-ray Computed.

Fig. 1. Clinical photograph shows a round mass occupying the right preauricular region (arrow).

Fig. 2. Panoramic radiograph shows no pathological changes associated with the lesion in the right parotid gland area.

Fig. 3. Axial (A) and coronal (B) contrast-enhanced computed tomography scans show an encapsulated and homogeneously enhanced multilocular soft tissue mass on the right parotid gland.

Fig. 4. Axial (A) and coronal (B) T1-weighted magnetic resonance (MR) images show a well-defined homogeneous hypointense mass of the right parotid gland area. Axial (C) and coronal (D) T2-weighted MR images show the ovoid mass with multilocular hyperintensity and a partially hypointense signal. Axial (E) and coronal (F) fat-suppressed enhanced T1-weighted MR images show the lesion with a high signal along the lobulated margin and an internal homogeneous low signal.

Fig. 5. Surgical specimen measuring 3.9 cm × 2.9 cm in diameter shows the encapsulated smooth mass.

Fig. 6. A. A significant cystic change (black asterisk) and multiple small cysts inside the mass are observed (hematoxylin and eosin [H&E] stain, ×40). B. Hemorrhages are observed in the lumen (H&E stain, ×100). C. Spindle-shaped Schwann cells form a palisaded arrangement around the eosinophilic area (Antoni A, red arrow). Spindle cells are arranged with a loose and myxomatous stroma. (Antoni B, blue arrow) (H&E stain, ×200). D. Spindle-shaped cells are positive for S-100 protein (immunohistochemical stain, ×200).