There were only 198 Chinese and English literatures on carcinomas derived from myoepithelial cells in head and neck regions (CMCHN) from 1963 to 2020, most of which were case reports. These myoepithelial cell differentiated malignancy were indistinguishable, and immunohistochemical results were often required in the pathological diagnosis of these diseases. S-100 protein, vimentin and cytokeratin (CK) were the most sensitive markers of MEC.Double-layer tubular structure of EMC could be identified by CK staining for glandular epithelial cells in the inner layer, and by S-100 and smooth muscle actin (SMA) antibody staining for clear outer layer of myoepithelial cells.AdCC also presented a tubular structure composed of two layers of cells. Unlike EMC, S-100 protein staining was only positive in the inner layer of AdCC.
CMCHNs have been observed in the gingiva, palate and tongue, larynx, parapharynx, nasopharynx, nasal cavity, nasal sinus, lacrimal gland, inferior temporal fossa, etc[17, 18]. And literatures reported that approximately 75% of EMC[19, 20] originated from the parotid gland, 10% from the submandibular gland, 10–15% from the salivary glands, and the remaining occurred in the palate, maxillary sinus, nasal cavity, trachea, and the root of the tongue. The AdCC accouted for 28% in malignant submandibular gland tumors, making it the most common malignant salivary gland tumor in this region. Patients might survive for years with metastases because this tumors were generally well-differentiated and slow-growing.
Our results showed that the incidence of these diseases was low, and only one patient (6.7%) died from the disease over the last decade. Despite this, our study demonstrated high recurrence rate, since 40% of the patients with CMCHN had recurrences after primary treatments, among which, 26.7% were local-regional recurrences, and 20% were distant metastases. These results were consistent with previous reports showing high incidences of local-regional recurrence and distant metastasis in patients with CMCHN[9–11]. In this study, the treatment was mainly complete surgical resection. Extended resection, lymph node dissection and chemoradiotherapy were important treatments for patients suffering from recurrence.
Due to the low incidence and varied biologic behaviors, limited evidences can be refered by physicians to predict outcome and determine management strategies. The correlation between the high recurrence potential and myoepithelial differentiation of this disease needs further laboratory verification. Meanwhile, the targeted therapy to reduce the recurrence rate is also worth of attention.