A relatively rare disease, epithelial-myoepithelial carcinoma mostly develops in the
parotid gland, but some reports claim that it also occurs in the nasal cavity, paranasal
sinus, nasopharynx, bronchus, lung, lacrimal gland, submandibular gland, and base
of the tongue 2], 4], 5]. To the best of our knowledge, only one other case of epithelial-myoepithelial carcinoma
in the subglottic region has been reported previously 6].
It has been highlighted that epithelial-myoepithelial carcinoma develops more commonly
in women and has a higher incidence in the fifth to eighth decades. The symptoms of
epithelial-myoepithelial carcinoma vary depending on its anatomic position. When it
intrudes into the parotid gland, the symptoms vary from subclinical tumentia to facial
nerve palsy. When it encroaches into the larynx, as found in our case, various symptoms
can occur depending on the carcinoma’s size, ranging from no symptoms to voice changes
and respiratory obstruction 2], 4], 5].
Epithelial-myoepithelial carcinoma is diagnosed using an optical microscope and immunohistochemistry.
On histology, epithelial-myoepithelial carcinoma is characterized by the presence
of tubules with two distinct types of cells. The main histological features are epithelial
cells in the inner layer of the lumen and myoepithelial cells surrounding the outer
layer 2], 7]. These features are similar to those of intercalated ducts. Although it is helpful
for diagnosis to confirm the presence of both cell groups with hematoxylin-and-eosin
staining, the key to diagnosis involves clarifying the exact cell composition. In
immunohistochemical analysis, myoepithelial cells in the outer layer are positive
for calponin, p63 protein, glial fibrillary acidic protein, S-100 protein, and SMA.
Epithelial cells in the inner layer are positive for cytokeratin-7 and epithelial
membrane antigen 7]. In our case, the outer myoepithelial cells tested positive for SMA and p63, while
the inner epithelial cells were positive for cytokeratin; hence, epithelial-myoepithelial
carcinoma was diagnosed.
Other diseases that should be considered in the differential diagnosis of epithelial-myoepithelial
carcinoma are pleomorphic adenoma, myoepithelial carcinoma, and adenoid cystic carcinoma
8]. Epithelial-myoepithelial carcinoma with a large amount of stroma resembles a mixed
tumor, but invasiveness indicates the presence of a carcinoma 9]. The local morphological features of epithelial-myoepithelial carcinoma can be observed
in adenoid cystic carcinoma and acinic cell carcinoma. Thus, these carcinomas should
be widely excised to distinguish them from aggressive malignant tumors like epithelial-myoepithelial
carcinoma.
Epithelial-myoepithelial carcinoma is regarded as a low-grade-malignancy tumor and
the treatment protocol involves wide surgical excision with secure clear margins.
Simple excision should be avoided because epithelial-myoepithelial carcinoma often
has a destroyed epithelium 8], 10]. In the previous report, surgery was repeated several times because of local recurrence,
but in our case, we completely removed the tumor by carbon dioxide laser surgery.
Although postoperative radiotherapy is generally performed to reduce local recurrence,
the effect of chemotherapy is not yet clear 2], 8]. It is known that tumors 4 cm are often associated with local recurrence. Therefore,
when a large tumor is present, it is important to monitor the patient’s postoperative
status in the outpatient clinic. Notably, a case was reported where distal metastasis
was found near the facial nerves, kidneys, brain, and lungs, and another where distal
metastasis was found 28 years after surgery 8], 11].