Epithelial-myoepithelial carcinoma of the nasopharynx: A case report and review of the literature

Abstract

Background: Epithelial-myoepithelial carcinoma (EMCa) is a rare low-grade malignant tumor that most commonly occurs in the salivary glands, with approximately 320 cases having been reported worldwide. Here, we report the third case of EMCa occurring in the nasopharynx. Rare cases in the breast, pituitary gland, lacrimal gland, nose, paranasal sinus, nasal cavity, trachea and bronchus, lung, and even the pleura mediastinalis have also been reported. Histopathology and immunohistochemistry are useful for confirming the diagnosis of EMCa, which is characterized by biphasic tubular structures composed of inner ductal and outer clear myoepithelial cells and stains for different markers in each layer. However, because of the rarity of EMCa, the clinicopathological characteristics and treatment of these patients remain unclear.

Case presentation: We report a rare case of EMCa of the nasopharynx. A 51-year-old man presented with a 5-month history of pain while swallowing and aggravation accompanied by right ear tinnitus lasting for 1 month. Nasopharyngoscopy and magnetic resonance imaging (MRI) of the nasopharynx and neck revealed a 5.6 cm × 3.4 cm × 3.1 cm mass in the nasopharyngeal space, invasion of the right cavernous sinus, and lymph node enlargement in the right retropharyngeal space. On 17 April 2019, based on the histopathological and immunohistochemical features, a final diagnosis of EMCa of the right nasopharynx was made. The patient underwent concurrent chemoradiotherapy (CCRT), and his symptoms were relieved after treatment. On 10 January 2022, nasopharynx MRI and biopsy revealed local recurrence, but chest and abdominal computed tomography (CT) showed no obvious signs of metastasis. The local recurrence-free survival (LRFS) period was 33 months.

Conclusion: To the best of our knowledge, this is the third reported case of EMCa in the nasopharynx and the only case of EMCa in the nasopharynx treated with CCRT, and a partial response was achieved. Therefore, to improve the quality of life and prognosis of patients with unresectable tumors, we believe that CCRT is a suitable option. Further clinical observations are required to elucidate the pathophysiology and prognosis of EMCa.

Keywords: case report; concurrent chemoradiotherapy; epithelial–myoepithelial carcinoma; immunohistochemistry; nasopharynx.

Figure 1

Nasopharynx and neck MRI findings from 15 April 2019. (A–D) The axial planes of T1-weighted, enhanced T1-weighted, T2-weighted, and diffusion-weighted imaging (DWI) MRI of the nasopharynx, showing a 5.6 cm × 3.4 cm × 3.1 cm mass within the right parietal and lateral walls of the nasopharynx, accompanied by skull base bone invasion, invasion of the oropharyngeal lateral wall and right parapharyngeal space, the right medial pterygoid muscle, and the musculus longus capitis. (E, F) The axial planes of enhanced T1-weighted DWI MRI revealed enlargement of the right retropharyngeal lymph node. (G) The coronal plane of enhanced T1-weighted imaging showed tumor involvement with the cavernous sinus.

Figure 2

Pathological findings of the nasopharyngeal biopsy obtained on 17 April 2019. The EMCa of the nasopharynx was mainly composed of an inner layer of epithelial cells and an outer layer of clear cytoplasmic myoepithelial cells. H&E staining; magnification, ×10 (A) and ×40 (B). EMCa, epithelial–myoepithelial carcinoma; H&E, hematoxylin and eosin.

Figure 3

Nasopharynx and neck MRI findings from 29 July 2019. (A–D) The axial planes of T1-weighted, enhanced T1-weighted, T2-weighted, and DWI and (E) the coronal plane of enhanced T1-weighted MRI, showing that the nasopharyngeal lesions on the right side subsided significantly, but there was a 4.8 cm × 3.0 cm × 2.7 cm residual area of low signal and no enhancement, which suggested necrosis.

Figure 4

Nasopharynx and neck MRI findings from 7 July 2020. (A–D) The axial planes of T1-weighted, enhanced T1-weighted, T2-weighted, and DWI and (E) the coronal plane of enhanced T1-weighted MRI, showing that the nasopharyngeal lesions and the necrotic area had subsided significantly. However, there was still a residual area of inhomogeneous enhancement in the right nasopharynx and parapharyngeal space, demonstrating restricted diffusion on DWI.

Figure 5

Nasopharynx and neck MRI findings from 27 April 2021. (A–D) The axial planes of T1-weighted, enhanced T1-weighted, T2-weighted, and DWI and (E) the coronal plane of enhanced T1-weighted MRI, showing that the residual area of inhomogeneous enhancement had shrunk.

Figure 6

Nasopharynx and neck MRI findings from 10 January 2022. (A–D) The axial planes of T1-weighted, enhanced T1-weighted, T2-weighted, and DWI and (E) the coronal plane of enhanced T1-weighted MRI, showing an area of enhancement in the right nasopharyngeal and parapharyngeal space. DWI demonstrated slightly restricted diffusion, which was considered indicative of recurrence.

Figure 7

Pathological findings of the nasopharyngeal biopsy obtained on 12 January 2022. Nasopharyngeal EMCa recurrence was considered. H&E staining; magnification, ×4. EMCa, epithelial–myoepithelial carcinoma; H&E, hematoxylin and eosin.

Figure 8

Immunohistochemistry test results of the nasopharyngeal biopsy obtained on 17 April 2019. (A) CK7 positivity was observed in epithelial cells. (B–D) P63, SMA, and VIM positivity was observed in myoepithelial cells. (E–G) CK, EGFR, and CD117 positivity was observed in tumor cells. (H) Ki-67 positivity was observed in 35% of the tumor cells. (I–L) MLH1, MSH2, MSH6, and PMS2 positivity was observed in tumor cells. (M–O) Actin, GFAP, and S-100 negativity was observed in tumor cells. (P) PD-L1 positivity was observed in less than 1% of tumor cells and in 10% of stromal cells (magnification, ×10). CK, cytokeratin; SMA, smooth muscle actin; VIM, vimentin; EGFR, epidermal growth factor receptor; GFAP, glial fibrillary acidic protein; PD-L1, programmed death ligand-1.

Figure 9

Immunohistochemistry test results of the nasopharyngeal biopsy obtained on 18 January 2022. (A) CK7 positivity was observed in epithelial cells. (B–D) P63, SMA, and VIM positivity was observed in myoepithelial cells. (E–G) CK, CK5/6, and S-100 positivity was observed in tumor cells. (H) Ki-67 positivity was observed in 15% of tumor cells (magnification, ×4). CK, cytokeratin; SMA, smooth muscle actin; VIM, vimentin.