Korean J Radiol. 2001 Jan-Mar;2(1):42-51. English. Published online Mar 31, 2001. https://doi.org/10.3348/kjr.2001.2.1.42 | |
Copyright © 2001 The Korean Radiological Society |
Se Hyung Kim, MD,1 Moon Hee Han, MD,2 Sun Won Park, MD,1 and Kee-Hyun Chang, MD2 | |
1Department of Radiology, Seoul National University College of Medicine, Seoul, Korea. | |
2Institute of Radiation Medicine, Seoul National University College of Medicine, Seoul, Korea. | |
Address reprint requests to: Moon Hee Han, MD, Department of Diagnostic Radiology, Seoul National University Hospital, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Korea. Telephone: (822) 760-3602, Fax: (822) 743-6385, | |
Received September 09, 2000; Accepted January 07, 2001. | |
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-
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Abstract
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Because the tongue is superficially located and the initial manifestation of most diseases occurring there is mucosal change, lingual lesionscan be easily accessed and diagnosed without imaging analysis. Some lingual neoplasms, however, may manifest as a submucosal bulge and be located in a deep portion of the tongue, such as its base; their true characteristics and extent may be recognized only on cross-sectional images such as those obtained by CT or MRI.
Some uncommon tongue neoplasms may have characteristic radiologic features, thus permitting quite specific radiologic diagnosis. Lipomas typically manifest at both CT and MR imaging as homogeneous nonenhancing lesions. Relative to subcutaneous fat they are isoattenuating on CT images, and all MR sequences show them as isointense. Due to the paramagnetic properties of melanin, metastases from melanotic melanoma usually demonstrate high signal intensity on T1-weighted MR images and low signal intensity on T2-weighted images.
Although the radiologic findings for other submucosal neoplasms are nonspecific, CT and MR imaging can play an important role in the diagnostic work-up of these unusual tumors. Delineation of the extent of the tumor, and recognition and understanding of the spectrum of imaging and the pathologic features of these lesions, often help narrow the differential diagnosis.
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Keywords:
Tong; Tong, MR; Tong, neoplasms
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Although the vast majority of lingual tumors are squamous cell carcinomas, a variety of non-squamous cell neoplasms may affect the tongue. Most squamous cell carcinomas first manifest with mucosal change and can be easily accessed and diagnosed without imaging analysis. Some non-squamous cell neoplasms, however, may manifest as a submucosal bulge and be located in a deep portion of the tongue such as its base. Thus, the characteristics and extent of these lesions may be recognized only on cross-sectional CT or MR images.
In this article, we describe the imaging findings of uncommon non-squamous cell neoplasms of the tongue provide clinical and pathologic-radiologic correlation, and discuss the clinical role of CT and MR imaging in the diagnostic work-up of these lesions.
Lipoma
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Although lipoma is the most common of all connective tissue lesions, it is rarely found in the tongue. When it does occur there, it is localized immediately beneath the mucosa and is seen at the organ's lateral edge and in the anterior two-thirds.
The radiologic diagnosis of lipoma is straightforward: in virtually all cases both CT and MR imaging provide a definitive diagnosis. On CT, lipoma typically manifests as a homogeneous nonenhancing lesion with attenuation values of between -65 HU and -125 HU (1). All MR pulse sequences show that the lesion is isointense relative to subcutaneous fat (i.e. hyperintense on T1-weighted images, moderately intense on T2-weighted images, and hypointense on fat-suppressed T1-weighted images) (Fig. 1).
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Schwannoma
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Schwannoma is a solitary tumor of the Schwann sheath of the cranial, sympathetic or peripheral nerves. About 25% of all extracranial schwannomas are located in the head and neck, the lateral cervical region and the mouth being the most common sites. Schwannomas arising from the base of the tongue are very rare (2). Tumors are generally well encapsulated and their growth is slow. As they become larger they tend to outgrow their blood supply and undergo cystic degeneration in some areas. Histologically, schwannoma of the tongue is characterized by regimented pallisading of cells.
Radiologically, most schwannomas are shown by non-enhanced CT to be well-circumscribed, dense, homogeneous soft-tissue masses which exhibit contrast enhancement. Calcification or hemorrhage is uncommon, but cystic or fatty degeneration is frequent. Most schwannomas appear hypointense or isointense relative to muscle on T1-weighted images, hyperintense on T2-weighted images, and show strong enhancement after contrast administration (Fig. 2). In our case, because the tumor occurred in the region of the foramen cecum, the possibility of ectopic thyroid was considered (Fig. 2).
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Myoepithelioma
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Myoepithelioma is a rare salivary gland tumor composed entirely of myoepithelial cells. Although these are an important element in many salivary gland tumors, pure myoepithelioma is rare, accounting for less than 1% of all such tumors (3). Malignant myoepithelioma is even rarer. The parotid gland is by far the most frequently affected site; myoepithelioma arising from the base of the tongue has not been reported.
Myoepithelioma is biologically benign in the majority of cases, but occasionally infiltrates locally and metastasizes to other organs including the inguinal lymph node.
The imaging features of this tumor strongly suggest a benign mass (Fig. 3), but using current imaging modalities it cannot be differentiated from other benign lesions unless a biopsy is performed.
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Hemangioma
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Hemangioma is the most common tumor of infancy. On the basis of the cellular features described by Mulliken and Glowacki in 1982, vascular lesions may be classified as either hemangioma or vascular malformation (4). They proposed that the term 'hemangioma' should be limited to those lesions that show increased mitotic activity. Most hemangiomas are present at birth, but some do not manifest clinically until early childhood. They may regress spontaneously due to internal bleeding, thrombosis, or organization. The most common sites of oral occurrence are the lip, buccal mucosa, tongue, and palate.
Angiographically, a hemangioma appears as a well-circumscribed mass characterized by the presence of a lobular pattern of intense, persistent tissue staining (5) (Fig. 4). Arteriovenous shunting and high flow are frequent, but do not permit differentiation from vascular malformations.
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On CT, hemangioma usually appears as a well demarcated enhancing mass that often contains calcified phleboliths. MR imaging shows the lesion as a solid mass with iso- or slightly high signal intensity to muscle on T1-weighted images and heterogeneous signal intensity on T2-weighted images. Postcontrast T1-weighted imaging commonly demonstrates prominent enhancement (Fig. 4). Due to the presence of multiple low signal intensity vessels with rapidly flowing blood, some hemangiomas have a typical serpentine appearance (Fig. 4). The conspicuity of these signal void areas increases with tumor size.
Adenoid cystic carcinoma
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Adenoid cystic carcinoma is the most common malignant tumor of the minor salivary glands and accounts for 10~51% of all malignant lingual tumors. It is well known for its propensity to spread through perineural spaces. Dysphagia, a tongue mass and pain are the most common presenting symptoms. A history of pain, suggesting neural invasion by the tumor, is associated with poor prognosis. The tumor is classified histologically as one of three types: cribriform, tubular, or solid or basaloid.
At the time of diagnosis, both CT and MR imaging usually depict extensive submucosal spread. The signal intensity demonstrated by MRI and the pattern of contrast enhancement revealed by CT and MRI are nonspecific (Fig. 5), and differentiation from other types of tumor is therefore difficult. Nevertheless, low signal intensity on T2-weighted MR images appears to correspond to highly cellular tumors (solid type) with poor prognosis, whereas high signal intensity appears to correspond to less cellular tumors (cribriform or tubular type) with better prognosis (6) (Fig. 5).
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Mucoepidermoid carcinoma
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Mucoepidermoid carcinoma occurs most commonly in the parotid gland; one which arises from the tongue is unusual. This tumor can be classified histologically as low, intermediate or high grade, and grade correlates well with prognosis (7). Metastasis is primarily to subcutaneous tissues, lymph nodes, bone and the lung. Surgery is the treatment of choice, with wide local excision.
The radiologic features of lingual mucoepidermoid carcinoma are nonspecific (Fig. 6), while the CT findings vary with the grade of the tumor. Low-grade lesions are benign in appearance, with apparently well-delineated smooth margins, whereas high-grade lesions have indistinct infiltrating margins. In our case, however, the tumor had a poorly defined margin despite its low-grade histologic features (Fig. 6). Due to the high cellularity of this tumor, both T1- and T2-weighted MR images tend to demonstrate low to intermediate signal intensity (Fig. 6).
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Epi-myo-epi carcinoma
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Epi-myo-epi carcinoma is an uncommon low-grade tumor occurring mainly in the parotid gland. Tumors are bulky and bosselated, grow slowly, and develop mostly in elderly people. The appellation "epi-myo-epi" is derived from the fact that the tumors form distinctive epithelial tubules or ductules surrounded by neoplastic myoepithelial cells (8) (Fig. 7).
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Lymphoma
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Lymphoma is the third most common malignant lesion to occur in the oral region, though because the oral cavity contains only small amounts of lymphoid tissue, extranodal lymphoma in this area is less common (9). The favored intraoral sites of lymphoma are palatal mucosa and bone, and the most common symptoms are local swelling, pain and discomfort in the throat, or an ulcer. Prognosis depends on tumor stage, the aggressiveness of the malignant cell type, and response to treatment (9). Oral lesions seem to be quite sensitive to irradiation (9). Prognosis is worst in cases involving the tongue, and best where the parotid region or tonsils are affected.
CT demonstrates that lymphoma is isodense to muscle. Although the tumor has no specific imaging characteristics or pathognomonic signs, if more than one extranodal mass is detected, if the mass is huge and there is neither necrosis nor ulceration, or if the mass is associated with large, nonnecrotic nodes, a diagnosis of lymphoma is suggested (Fig. 8). On MR images, lymphoma is isointense to normal muscle on T1-weighted images and hypointense on T2-weighted images. Enhancement is variable.
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Metastasis
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Primary tumors which metastasize to the oral cavity are extremely rare. The gingiva is the most common site, and the tongue the second most common. The two common primary sites from which metastasis to the tongue occurs are the lung and kidney. Possible routes include the systemic, venous, and lymphatic circulation (10). The systemic route is most common. Because of its rich vascular supply and relative immobility compared to other parts of the tongue, the base of this organ is most frequently involved (10). Metastasis to the tongue often occurs at a late stage when there is disseminated disease; prognosis is therefore very poor and only palliative treatment is possible.
In most cases, the radiologic features of lingual metastases are nonspecific: in our case, metastasis mimicked primary carcinoma (Fig. 9). Due to the paramagnetic properties of melanin, however, the typical MR imaging features of metastases from melanotic melanoma are high signal intensity on T1-weighted images and intermediate to low signal intensity on T2-weighted images (Fig. 10). In addition, strong enhancement is noted after the administration of contrast material.
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References
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Corio RL. Epithelial-myoepithelial carcinoma. In: Ellis G, Auclair P, Gnepp D, editors. Surgical pathology of the salivary glands. Philadelphia, Pa.: WB Saunders Co.; 1991. pp. 100-109.
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