Myoepithelioma of parotid gland presenting as infra‐auricular subcutaneous mass

Abstract

Myoepithelioma is a rare but well-characterized group of tumours, among which myoepithelioma of the salivary glands is the best known. We report two patients with myoepithelioma of parotid gland presenting as infra-auricular subcutaneous mass. The lesions were clinically suspected to be epidermal cyst. The biopsies revealed that most of the tumour cells showed epithelioid features with oval or spindle eosinophilic cytoplasm. No ductal or syringomatous epithelial structures were observed. The tumour cells showed cytoplasmic immunoexpressions of vimentin, cytokeratin (AE1/AE3), S-100 protein and smooth muscle actin (SMA). In one patient, a strong calponin positivity was observed. Maguetic resonance imaging (MRI) of both patients revealed exophytic, well-defined, strongly enhancing mass in superficial lobe of parotid gland, confirming the parotid gland origin. Myoepithelioma of parotid gland can be presented as a slowly growing tumour of pre- or infra-auricular area. In dermatologic department, it can be misdiagnosed as various dermal or subcutaneous tumours.

Myoepithelioma of the Parotid Gland Presenting as a Retroauricular Cutaneous Nodule: A Case Report

“…The myoepitheliomas invariably express CK and hence, its absence would militate against this diagnosis [12,13]. Vimentin and S-100 protein, which T1-weighted images and with a mid-hyperintensity being seen on the fat-saturated T2-weighted images.…”

“…The patient remained tumour-free at 1-year of the follow-up. usually are not present in the normal myoepithelial cells, are very sensitive markers of a neoplastic myoepithelium [12,13]. Because a neoplastic transformation causes the myoepithelium to lose or modify its smooth-muscle phenotype, immunohistochemical studies which demonstrate the smooth-muscle differentiation in these cells have been less useful.…”

“…Sheldon AT et al, [13] detected smooth-muscle actin and a muscle-specific action in 50 and 31% of the tumours, respectively. It was also suggested that the tumour cells in the myoepitheliomas are positive for the glial fibrillary acid protein andcalponin [12,13].…”

“…To avoid such a possibility, the relationship of the cutaneous mass between the salivary gland and the adjacent structures, such as the muscles and the soft tissues, including the skin, should be examined prior to the surgery by CT or MRI [12]. In our case, although on the basis of the radiographical findings, the tumour was suspected to be malignant, a presurgical evidence of a preserved facial nerve function contributed to its consideration, with a strong possibility, a benign tumour.…”

“…The first choice is surgery. The mass should be totally removed with a margin of normal gland tissue [12] and the tumour origin, whether it is the parotid gland or otherwise, must be detected in the surgical specimen [12].…”