Epithelial-myoepithelial carcinoma of the tongue base: a case for the case-report and review of the literature
© Peters et al; licensee BioMed Central Ltd. 2010
Received: 31 December 2009
Accepted: 2 February 2010
Published: 2 February 2010
A 60 year old lady was referred to the Princess Alexandra Hospital (Brisbane, Queensland, Australia) tertiary Otolaryngology, Head and Neck Unit from a peripheral hospital for investigation and management of a tumour at the base of the tongue. Biopsy of the tumour revealed it to be an epithelial-myoepithelial carcinoma of the base of the tongue. This is an extremely rare tumour in this location with only 2 other case reports in the world literature: the patients were treated with chemo-radiotherapy and surgery respectively. Our patient was made aware of the world literature and was able to make a fully informed decision on her choice of treatment modality and was treated with radiotherapy. Increasingly journals are limiting publication of case reports to "world firsts" only. We present a case where such a policy would have denied patient choice and possibly led to detrimental treatment.
We review the world literature of tongue base epithelial-myoepithelial carcinoma of the tongue.
Epithelial-myoepithelial carcinoma is an rare tumour occurring in the salivary glands, (most commonly in the parotid gland), with a reported incidence of between 0.2%  and 1% [2, 3] of salivary duct tumours. It is a hybrid tumour, composed of two different tumour entities, each of which conforms to a defined tumour category [4, 5] and based upon the Salivary Gland Register at the University of Hamburg. Specimens collected between 1965 and 1994 showed that only 0.1% of salivary gland tumours were hybrid tumours . Other examples of hybrid tumours include mucoepidermoid carcinoma, basaloid-squamous carcinoma, adeno-squamous carcinoma, sarcomatoid carcinoma and carcinoma in pleomorphic adenoma with differentiation as squamous cell carcinoma as well as adenocarcinoma .
A 60 year old lady was referred to the Princess Alexandra Hospital Head and Neck Clinic in July 2009 following a biopsy taken from a suspected tumour at the base of the tongue (BOT). The patient was referred to our unit for ongoing investigation and management. She had noted a one year history of dysphagia and difficulty in moving her tongue. Our patient also noted an unintended a 25 kg weight loss over the past year and had had a PEG feeding tube inserted in the interim before being referred to our department. The patient confirmed that she was an ex-smoker with a 30 pack year history but denied alcohol consumption.
Histology results for biopsy
Positive in basal cells (nuclear)
Positive in luminal cell (cytoplasmic); positive in basal cell (Golgi)
Positive in luminal cell (cytoplasmic); positive in basal cell (Golgi)
Positive in basal cells
Positive in luminal cells
Planning by the Radiation Oncology team was undertaken with a view to a 60 Gy treatment over 30 fractions with a 2 cm margin around the primary tumour. Her treatment was well tolerated although she did require daily hyoscine injections to dry up excessive secretions. She has had a complete clinical response and will be followed with a new MRI in 6 months.
Comparison of previous cases
Puri et al 2004 
Kumai et al 2006 
Peters et al
Male 48 yo
Male 76 yo
Female 60 yo
Base of Tongue Location
50 mm × 30 mm
40 mm × 20 mm
3 drug Chemotherapy (cisplatin, doxorubicin and 5-Fluorourcil) Radiotherapy (66 Gy) (Coblalt Teletherapy Unit)
Surgery (subtotal glossectomy, bilat neck dissection and rectus abdominis flap)
Radiotherapy, 60 Gy over 30 fractions, 2 cm margin
Nil Recurrence (14 months)
Nil recurrence (19 months)
Complete clinical response
These two cases were both published as "world firsts" and whilst sharing a common histology of tumours in an identical location (base of tongue), were where managed in different ways. This allowed our team to present the patient with options for management of her rare tumour.
There are three major salivary glands--parotid, submandibular, and sublingual--as well as innumerable minor salivary glands distributed throughout the mucosa of the oral cavity and nasopharynx. All these glands are subject to inflammation or to the development of neoplasms . These glands give rise of over 30 histologically distinct tumours .
Histologic Classification and Incidence of Benign and Malignant Tumours of the Salivary Glands 
Pleomorphic adenoma (50%) (mixed tumour)
Mucoepidermoid carcinoma (15%)
Warthin tumour (5% to 10%)
Adenocarcinoma (NOS) (10%)
Acinic cell carcinoma (5%)
Other adenomas (5% to 10%)
Adenoid cystic carcinoma (5%)
Basal cell adenoma
Malignant mixed tumour (3% to 5%)
Squamous cell carcinoma (1%)
Other carcinomas (2%)
Epithelial-myoepithelial carcinomas are defined, histologically, by tubular or ductal structures lined by both basal myoepithelial cells and luminal epithelial cells similar to normal intercalated salivary gland ducts. Whilst neoplasms are monoclonal and, as such, comprise one cell type, there are uncommon tumours at all sites which show divergent differentiation. In some case, as for this tumour, this can be explained by the common precursor cells for both of the cell types represented in tis particular tumour.
Immunohistochemistry for expression of different cell proteins is essential in identifying the two cell types demonstrated in this tumour. The outer basal or myoepithelial cell layer expresses p63 (figure 8), low molecular weight cytokeratins (CK5/6) and variably expresses other cytokeratin subclasses because these cells unique in expressing both epithelial and smooth muscle characteristics reflecting their normal function of lining ducts AND being capable of contraction to aid salivary fluid flow. The inner luminal layer is typical of all epithelial cells in expressing cytokeratin but not smooth muscle proteins.
This tumour displayed the typical and characteristic features of Epithelial-Myoepithelial Carcinoma with an inner luminal epithelial layer (cytokeratin positive only Figures 7 & 9) and an outer myoepithelial cell layer (cytokeratin positive Figure 9) and co-expression of smooth muscle proteins (Figures 8 & 10).
Epithelial-myoepithelial carcinomas, whilst rare, most commonly occur in the parotid gland, but as with all salivary gland tumours, may arise anywhere in the naso-oro-pharynx in relation to minor salivary glands. By definition, an epithelial-myoepithelial carcinoma is a hybrid tumour, which is a tumour consisting of two distinctly different entities, each of which conforms to an exactly defined tumour category .
Epithelial-myoepithelial are, low grade malignant tumours although some tumours do exhibit more rapid growth and high grade behaviour. Histologically the high grade tumours show evidence of dedifferentiation which is not seen otherwise. Tumour behaviour can, therefore to some extent, be predicted by histologic features. In this case, the prediction would low grade malignancy.
During a study of 954 consecutive salivary gland tumours, Fonseca et al  found 22 epithelial-myoepithelial carcinomas (2.3%). In all these cases, the tumours were excised with the associated salivary gland. Follow up of these patients indicated a recurrence rate of 41% with a 5 year survival rate of 87.5% and a 10 year survival rate of 67.5%. This rate of recurrence was similar to what was observed by Corio et al (39%) .
A review of the literature has revealed only two previous instances at the base of tongue [6, 10] which were treated with chemo-radiation and surgery respectively without recurrence over a year later. Surgery and chemo-radiation are the two treatment modalities reported in the literature to have been used in base of tongue tumours and it is extremely helpful in a tertiary referral centre to have instant access to the only published experience with this particular tumour in this location.
It is important for very rare cases such as this to be reported particularly in respect of behaviour and treatment so as to build a database for these tumours. The current trend in journals not to publish case reports not only discourages junior researchers from getting on the publishing ladder but, as in our patient's case, could have severely limits evidence based options. Journals not publishing case report include CA: A Cancer Journal for Clinicians (Impact factor 2007 69.26) and the Journal of the American Medical Association (JAMA - Impact factor 2007 25.5), both highly respected journals with high ranking ISI impact factors.
Whilst the authors do not advocate that every journal should practice publishing case reports that have been published multiple times in the past, we would argue that limiting the world literature to "world firsts" will be to the detriment of our patients.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
One of the authors (CR) received travel and fellowship funding from the HCA international foundation and would like to thank them for their generosity.
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