Squamous cell carcinoma of the tongue has tobacco smoking and alcohol ingestion as major risk factors and spans two regions: the anterior two-thirds (oral tongue) is a common subtype of squamous cell carcinoma of the oral cavity whereas the posterior third (base of tongue) is considered part of the oropharynx.
Epidemiology and risk factors are similar to squamous cell carcinomas elsewhere in the upper aerodigestive tract, with tobacco smoking and alcohol ingestion being major risk factors 1-3,9.
Of note, the role of human papillomavirus (HPV) as an aetiological factor for squamous cell carcinoma is strongest in oral cavity (compared to other regions in the head and neck), with HPV DNA isolated from up to 50% of cases, and thought responsible for the tumour in over half of these 1-3.
Approximately 20% of all SCCs of the oral cavity arise from the tongue, and approximately 75% of all tongue SCCs arise from the anterior two-thirds of the tongue (oral part) 9.
Squamous cell carcinoma of the tongue usually arises from the ventrolateral aspect of the mid and posterior tongue, probably due to adjacent pooling of carcinogens 1. Despite the ease of inspecting the tongue by both patient and physician, they often present late, as they are usually painless and often ignored by the patient. Eventually, they present as a non-healing ulcer which demonstrates growth over time 6.
Due to the extensive lymphatic drainage of the tongue, nodal metastases are common (37-58%) 7,9 at the time of diagnosis (more common than any other site in the oral cavity) 6. A neck mass may, therefore, be the presenting complaint.
A common staging system is used for all squamous cell carcinomas of the oral cavity, with tumour staging being based on size and extension into adjacent structures. Nodal staging is the same as that used for SCCs of the oral cavity, oropharynx, hypopharynx and larynx (see: staging of oral cavity squamous cell carcinomas).
Whether CT or MRI is used the same features should be assessed 14:
- the size of tumour and tumour thickness
- extension across the midline
- extension beyond the intrinsic muscles of the tongue
- involvement of adjacent structures
- neurovascular bundle and submandibular duct in the floor of mouth
Lymphatic drainage of the tongue is extensive, accounting presumably for the high rate of nodal metastases present at the time of diagnosis. Drainage patterns depend on the location of the primary lesion 6:
- anterior tongue: level Ia nodes (submental nodes)
- lateral tongue
- posterior tongue: level II nodes (upper jugulodigastric nodes)
It is important to remember that significant lymphatic drainage occurs across the midline, and thus the nodes of both sides of the neck need to be carefully examined for the presence of nodal metastases.
The incidence of lymph node metastases correlates with tumour thickness, which is best assessed on coronal images 7.
The primary tumour can be assessed directly with a small high-frequency probe evaluate tumour thickness. Tumour thickness of ≤7 mm has a 12% risk of lymph node metastasis whereas a tumour thickness >7 mm has a 57% risk of lymph metastasis in one series of 65 patients 12.
Ultrasound is also used for assessment of cervical lymph nodes and to aid in FNAC of suspicious nodes.
CT is the most commonly used modality for assessment of tongue squamous cell carcinoma, able to both locally stage the tumour and assess for nodal metastases.
Lesions typically appear of soft tissue attenuation, usually a little more attenuating than normal tongue musculature (on account of the keratin) and enhance following contrast administration.
Bony algorithm thin section CT is the most sensitive modality for assessing early bony erosion.
Non-contrast scans of the neck may demonstrate increased attenuation of involved nodes due to keratin production by tumour deposits 8.
MRI is excellent at identifying the extent of tumour infiltration and is especially useful in patients with significant dental amalgam which causes artefact on CT 7,9.
- T1: intermediate to low signal
- T2: intermediate to high signal
- T1 C+ (Gd) with fat saturation: enhances
In larger lesions that abut the mandible, MRI is more sensitive than CT at identifying early marrow change (low T1 signal, high T2 signal, enhancement) but less sensitive at visualising cortical erosion 9.
Treatment and prognosis
For small tumours excision is possible with a hemiglossectomy or partial hemiglossectomy. Reconstruction of the tongue depends on the size of the defect. When less than a third of the tongue has been resected primary closure is possible. Larger defects require pedicle or free-flap reconstruction 1,4. Larger lesions which cross the midline, although sometimes technically resectable with a total glossectomy, are usually not resected due to the operation being poorly tolerated 1.
In tumours that extend laterally across the floor of the mouth and into the mandible, resection is challenging often requiring segmental mandibulectomy and reconstruction 5.
Radiotherapy is often used either in conjunction with surgery or alone in advanced cases.
The differential diagnosis of squamous cell carcinoma of the tongue is essentially that of other malignant lesions of the oral cavity as well as a few non-neoplastic lesions. It therefore includes:
- other malignancy
- infection: more a concern for the floor of mouth lesions, or those with involvement of the mandible
- normal adenoidal tissue: for a base of tongue lesion
- ultrasound is more reliable than MRI at estimating tumour thickness, which can direct the need for neck dissection 13
- post-biopsy oedema/haematoma can result in overestimation of tumour thickness 13
- 1. Head and neck imaging. Ed. by Peter M. Som, Hugh D. Curtin. St Louis (Mo.) : Mosby-Year Book, 2003. ISBN:0323009425 (find it at amazon.com)
- 2. Current Diagnosis and Treatment Surgery Thirteenth Edition. Gerard Doherty. McGraw-Hill Medical ISBN:0071635157 (find it at amazon.com)
- 3. Head and Neck Cancer. Louis B Harrison (Editor), Roy B Sessions (Editor), Waun K Hong (Editor). Lippincott Williams & Wilkins ISBN:0781771366 (find it at amazon.com)
- 4. Oral Cancer. J. w. Werning, John W. Fleming (Editor). Thieme Medical Publishers ISBN:1588903095 (find it at amazon.com)
- 5. Ballenger's Otorhinolaryngology Head and Neck Surgery, 17th edition. James B. Snow Jr., P. Ashley Wackym. Pmph USA ISBN:1550093371 (find it at amazon.com)
- 6. Perez and Brady's Principles and practice of radiation oncology. editors, Edward C. Halperin, Carlos A. Perez, Luther W. Brady; associate editors, David E. Wazer, Carolyn Freeman, Leonard R. Prosnitz. Philadelphia : Wolters Kluwer Health/Lippincott Williams & Wilkins, c2008. ISBN:078176369X (find it at amazon.com)
- 7. Okura M, Iida S, Aikawa T et-al. Tumor thickness and paralingual distance of coronal MR imaging predicts cervical node metastases in oral tongue carcinoma. AJNR Am J Neuroradiol. 2008;29 (1): 45-50. doi:10.3174/ajnr.A0749 [pubmed citation]
- 8. Hayashi T, Tanaka R, Taira S et-al. Non-contrast-enhanced CT findings of high attenuation within metastatic cervical lymph nodes in patients with stage I or II tongue carcinoma during a follow-up period. AJNR Am J Neuroradiol. 2003;24 (7): 1330-3. AJNR Am J Neuroradiol (full text) [pubmed citation]
- 9. Imaging of the Head and Neck. Mahmood F. Mafee, Galdino E. Valbasson, Minerva Becker, J. S. Lewin, S. G. Nour (Contributor), A. L. Weber (Contributor), M. Becker (Contributor). Thieme Medical Publishers ISBN:1588900096 (find it at amazon.com)
- 10. Sigal R, Zagdanski AM, Schwaab G et-al. CT and MR imaging of squamous cell carcinoma of the tongue and floor of the mouth. Radiographics. 1996;16 (4): 787-810. doi:10.1148/radiographics.16.4.8835972 - Pubmed citation
- 11. Ong CK, Chong VF. Imaging of tongue carcinoma. Cancer Imaging. 2006;6 (1): 186-93. doi:10.1102/1470-7330.2006.0029 - Free text at pubmed - Pubmed citation
- 12. Lodder WL, Teertstra HJ, Tan IB et-al. Tumour thickness in oral cancer using an intra-oral ultrasound probe. Eur Radiol. 2011;21 (1): 98-106. doi:10.1007/s00330-010-1891-7 - Free text at pubmed - Pubmed citation
- 13. Yesuratnam A, Wiesenfeld D, Tsui A et-al. Preoperative evaluation of oral tongue squamous cell carcinoma with intraoral ultrasound and magnetic resonance imaging-comparison with histopathological tumour thickness and accuracy in guiding patient management. Int J Oral Maxillofac Surg. 2014;43 (7): 787-94. doi:10.1016/j.ijom.2013.12.009 - Pubmed citation
- 14. Law CP, Chandra RV, Hoang JK et-al. Imaging the oral cavity: key concepts for the radiologist. Br J Radiol. 2011;84 (1006): 944-57. Br J Radiol (full text) - doi:10.1259/bjr/70520972 - Free text at pubmed - Pubmed citation