Malignant peripheral nerve sheath tumor of facial nerve: Presenting as parotid mass
A 78-year-old male presented with a gradually increasing painful swelling over left side of the neck since 8 years. Physical examination revealed a mass in the lateral region of the neck behind the sternocleidomastoid muscle. The mass measured 7 cm in diameter and was tender and non-mobile. The overlying skin was unremarkable. Facial nerve function and the remainder of head and neck examination were normal.\nFine needle aspiration cytology (FNAC) was performed, which was suggestive of a cystic lesion of the salivary gland. Computed tomography (CT) scan showed centrally necrotic rounded mass lesion arising from parotid gland []. The lesion was almost completely replacing the outer lobe of left parotid gland and the inner lobe was normal. Anteriorly the lesion was seen abutting the masseter muscle and fat planes. CT findings suggested neoplastic lesion of the left parotid gland with involvement of bilateral submandibular nodes and left level II lymph nodes. Patient was taken up for surgery. Intra-operatively a 7 × 6 cm mass was seen involving the left parotid gland and all the branches of the facial nerve except the cervical branch. The facial nerve along with its branches was traced anteriorly. The entire tumor along with the parotid gland and the facial nerve was excised en block. The cervical branch of facial nerve was preserved.\nHistopathological examination revealed a tumor composed of spindle shaped cells with elongated hyperchromatic nuclei, arranged in long and short fascicles []. At places cells were arranged around hyaline bands in the form of cords and at places they were arranged in whorls. Some of the tumor cells had epitheloid appearance, while some cells had marked nuclear pleomorphism with tumor giant cells. In some areas, chondroid differentiation was seen. The stroma showed extensive areas of necrosis and hemorrhage. The blood vessels showed hyalinized walls. Mitotic figures were more than five per high-power field and areas of compressed parotid gland were present at the periphery of tumor.\nImmunohistochemically, the tumor cells showed diffuse and strong positivity for S-100, (Dako), however, were negative for Pan-cytokeratin (Dako, AE1/AE3), Desmin (Dako, D33), and Human Melanoma Black (HMB) 45 (Dako) [] and Vimentin (Dako). With the above features, a diagnosis of MPNST was made.\nPost-operatively, the patient had facial palsy [] and distant metastases were not found on whole body scan after 6 months of follow-up.