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Basal cell adenoma in the parapharyngeal space
Journal of Clinical Imaging 25 (2001) 392 – 395
Basal cell adenoma in the parapharyngeal space MR findings Ae Kyung Jeonga, Ho Kyu Leea,*, Sang Yoon Kimb, Kyung-Ja Choc a
Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Ku, Seoul 138-736, South Korea b Department of Otolaryngology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Ku, Seoul 138-736, South Korea c Department of Diagnostic Pathology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Ku, Seoul 138-736, South Korea Received 20 April 2001; accepted 18 May 2001
Abstract We report MR findings of a case of basal cell adenoma arising in the parapharyngeal space. On MR imaging, the mass was a wellcircumscribed cystic and solid tumor with a thin fibrous capsule and intratumoral hemorrhage. It was confined to the parapharyngeal space, separating from the deep lobe of the parotid gland. The solid portion of the tumor was slightly hypointense/hyperintense to the muscle on T1-/T2-weighted images and was relatively well enhanced on Gd-enhanced T1-weighted images. The cystic contents of the mass were hyperintense on both T1- and T2-weighted images and were proven to be a hemorrhage. D 2001 Elsevier Science Inc. All rights reserved. Keywords: MR, head and neck; MR, parapharyngeal space; MR, salivary gland; Basal cell adenoma, head and neck
1. Introduction Basal cell adenoma is a rare benign neoplasm of the salivary gland origin that derives its name from the basaloid appearance of the tumor cells. It occurs most frequently in the parotid gland, less commonly in the minor salivary glands of the upper lip, and uncommonly in the oral cavity, lower lip, hard palate, and submandibular gland [1 –3]. In the English literature, there have been no reports of basal cell adenoma occurring in the parapharyngeal space. We describe the MR findings of a patient with parapharyngeal basal cell adenoma.
2. Case report A 61-year-old woman was admitted with the complaint of a 7-year history of a bulging mass in the left oral cavity. She had had a fine needle aspiration biopsy at another
* Corresponding author. Tel.: +82-2-2224-4400; fax: +82-2-476-4719. E-mail address: [email protected] (H.K. Lee).
hospital 1 month previously. Microscopic examination at that hospital led to the diagnosis of a benign cyst. At the other hospital, a neck CT had been performed. A large well-circumscribed cystic and solid mass was found in the left parapharyngeal space and showed the heterogeneous, strong enhancement on contrast-enhanced CT scans (not shown). The preferred imaging diagnosis was schwannoma. One month later, an MR examination was performed at our hospital. On MR images, a well-encapsulated, round mass was found in the left parapharyngeal space, thereby obliterating the fat of the parapharyngeal space with partly peripheral displacement. The mass was composed of a central solid portion and a peripheral cystic portion with a thin rim. The solid portion was slightly hypointense on T1-weighted images and hyperintense to the muscle on T2-weighted images, which contained small hemorrhagic components (Fig. 1A,B). There was also relatively good enhancement on gadolinium-enhanced T1-weighted images (Fig. 1C). Cystic fluid was hyperintense on both T1- and T2-weighted images and was proven at surgery to be a hemorrhage (Fig. 1A,B). The capsule of the mass showed a hypointense, smooth thin rim on all MR sequences. The
0899-7071/01/$ – see front matter D 2001 Elsevier Science Inc. All rights reserved. PII: S 0 8 9 9 - 7 0 7 1 ( 0 1 ) 0 0 3 4 0 - 0
A.K. Jeong et al. / Journal of Clinical Imaging 25 (2001) 392–395
393
Fig. 1. A 61-year-old woman with a bulging mass in the left oral cavity. (A) Axial T1-weighted (450/12) MR image shows a well-marginated cystic and solid mass in the left parapharyngeal space (arrows). The mass obliterates the parapharyngeal fat and displaces the pharyngeal mucosal space medially, the internal carotid artery posterolaterally, and the longus colli muscle posteriorly. The central solid portion of the mass is slightly hypointense to the muscle and the peripheral cystic contents of the mass are hyperintense. The peripheral cystic contents was proven to be a hemorrhage. The capsule of the mass showed a hypointense, thin rim. The mass was separated from the deep lobe of the parotid gland by a fat plane. (B) Axial T2-weighted (3700/99) MR image at the same level A shows that the solid portion of the mass is relatively hyperintense to the muscle and the cystic contents are also hyperintense with a hypointense thin rim. (C) Contrast-enhanced axial T1-weighted (450/12) MR image at the same level, reveals good enhancement of the central solid portion, but only subtle enhancement of the peripheral rim. (D) Contrast-enhanced coronal T1-weighted (450/12) MR image shows that the mass occupies the left parapharyngeal space of the naso- and oropharyx (arrows) and has a hypointense rim. (E) Photomicrograph of the parapharyngeal mass (magnification 200, hematoxylin – eosin stain). The solid and trabecular tumor is composed of larger, lighter stained basaloid cells and peripherally located, palisading cells with small basophilic nuclei and scanty cytoplasm. (F) Gross findings of the parapharyngeal mass indicate that the cut surface of the mass is well-encapsulated, partly cystic, and solid. The solid portion is homogeneously yellowish white and myxoid on the cut surface. Hemosiderin is deposited along the peripheral rim and cystic walls.
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A.K. Jeong et al. / Journal of Clinical Imaging 25 (2001) 392–395
Fig. 1. (continued )
mass was separated from the deep lobe of the parotid gland by a fat plane, which displaced the pharyngeal mucosal space medially, the carotid sheath posterolaterally, the deep lobe of the parotid gland laterally, and the longus colli muscle posteriorly. On coronal images, the mass was confined to the left parapharyngeal space of the nasopharynx and oropharyx levels (Fig. 1D). There were no abnormal lymph nodes in either neck area. Excision of the mass was performed via a cervical approach below the mandible. The cut surface of the specimen was cystic and solid. The solid portion was yellowish white and myxoid with a central hemorrhagic component (Fig. 1F). Microscopic examination revealed interanastomosing trabeculae and tubules of monotonous basaloid cells in the cellular stroma composing the solid portion. The cystic spaces were lined with attenuated thin epithelium and contained some proteinaceous material. The cyst wall showed dense collagenous fibrous tissue with multifocal calcification, fresh hemorrhage, and hemosiderin-laden macrophages. The histopathologic diagnosis of basal cell adenoma was made (Fig. 1E), and the tumor was thought to have originated in the minor salivary gland in the parapharyngeal space.
3. Discussion Salivary gland tumors comprise less than 3% of all neoplasms of the head and neck. Basal cell adenoma is one of the rare, benign salivary gland neoplasms, accounting for only 2% of all tumors arising from the salivary glands [4]. Basal cell adenoma was once included in the category of monomorphic adenomas, which is an obsolete term. How-
ever, according to the 1991 classification of the World Health Organization, it is recommended to classify benign salivary tumors, other than pleomorphic adenomas, into several specific types, among them basal cell adenoma [3]. There is a nearly equal occurrence between males and females [5]. This tumor can occur at any age but occurs most often in middle-aged and older adults, with its peak occurrence during the seventh decade of life. Local excision of basal cell adenoma has been curative. Although recurrence is rare, the membranous subtype, which is a hereditary variety of basal cell adenoma, has been reported to have a 25 – 37% recurrence rate on some pathologic reports. Malignant transformation to basal cell adenocarcinoma is rare but has been suggested by some researchers [6]. The parapharyngeal space contains mainly fatty tissue, lymphatics, and minor salivary gland tissue, and is actually a potential space located lateral to the upper pharynx and extends from the skull base to the hyoid bone. This space may be the source of salivary gland tumors, as it was in this case [7]. The common clinical presentation of basal cell adenoma is a slow-growing, asymptomatic, freely movable mass [1,8]. Therefore, a deep-seated tumor can become a large mass before it becomes symptomatic. Microscopically, basal cell adenoma is characteristically composed of small isomorphic epithelial cells without myoepithelial cells or myxochondroid elements, as is typically seen in pleomorphic adenoma. This tumor is usually encapsulated by fibrous connective tissue with the cell masses separated by a thin cobweb-like stroma. This explains the low signal intensity of the tumor capsule on T2-weighted images, as was seen in this case. The growth patterns vary from solid or trabecular to tubular or canalicular [9].
A.K. Jeong et al. / Journal of Clinical Imaging 25 (2001) 392–395
Grossly, basal cell adenoma is solid or cystic, or gray or white and does not usually show intratumoral hemorrhage. In these characteristics, it is similar to pleomorphic adenoma. However, Triest et al. [3] reported that basal cell adenoma shows a characteristic vascular pattern in which small capillaries and venules are prominent in the microcystic areas of the adenoma. These vascular structures can cause intratumoral hemorrhage, as was seen in this case. The MR differential diagnosis for parapharyngeal tumors includes other tumors of minor salivary gland origin, nerve sheath tumors, and paragangliomas. Pleomorphic adenoma of a minor salivary gland tumor is the most common primary lesion arising in the parapharyngeal space. On MR images, it usually has heterogeneous intermediate signal intensity on T1-weighted images and intermediate to high signal intensity on T2-weighted images. Pleomorphic adenoma often shows cystic change. On MR images, it is difficult to make a differential diagnosis from the other parapharyngeal mass. It also displaces the carotid sheath posteriorly [10]. Schwannoma is usually located in the carotid space, therefore, it displaces the internal carotid artery anteromedially. It usually has heterogeneous signal intensity due to cystic change as well as hemorrhage, but it has strong enhancement on MR images. Paraganglioma usually displaces the internal carotid artery anteriorly because of its origin around the vagus
395
nerve in the carotid space. This hypervascular tumor has multiple focal and serpentine areas of low signal intensity representing vascular flow voids within the mass.
References [1] Neville BW, Damm DD, Allen CM, Bouquot JE. Salivary gland pathology. Oral and maxillofacial pathology. Philadelphia (PA): Saunders, 1995. p. 347. [2] Yamazaki T, Kotani A, Kawakami T. Basal cell adenoma of the sublingual gland. J Oral Maxillofac Surg 1987;45:270 – 3. [3] Triest WE, Fried MP, Stanievich JF. Membranous basal cell adenoma of the hypopharynx. Arch Otolaryngol 1983;109:774 – 7. [4] Mintz GA, Abrams AM, Melrose RJ. Monomorphic adenoma of the major and minor salivary glands. Oral Surg, Oral Med, Oral Pathol 1982;53:375. [5] Oslen KD. Tumors and surgery of the parapharyngeal space. Laryngoscope 1994;104:1 – 28. [6] Leegaard T, Lindeman H. Salivary gland tumors: clinical picture and treatment. Acta Otolaryngol 1970;263:155. [7] Ferreiro JA. Immunohistochemistry of basal cell adenoma of the major salivary glands. Histopathology 1994;24:539. [8] Esteves ARF, Dib LL, Carvalho LV. Basal cell adenoma: a case report. J Oral Maxillofac Surg 1997;55:1323 – 5. [9] Weiner AP. Monomorphic adenoma, canalicular variant. J Oral Surg 1977;35:414 – 5. [10] Som PM, Sacher M, Stollman AL, Biller HF, Lawson W. Common tumors of the parapharyngeal space: refined imaging diagnosis. Radiology 1988;169(1):81 – 5.
Basal cell adenoma in the parapharyngeal space MR findings Ae Kyung Jeonga, Ho Kyu Leea,*, Sang Yoon Kimb, Kyung-Ja Choc a
Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Ku, Seoul 138-736, South Korea b Department of Otolaryngology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Ku, Seoul 138-736, South Korea c Department of Diagnostic Pathology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Ku, Seoul 138-736, South Korea Received 20 April 2001; accepted 18 May 2001
Abstract We report MR findings of a case of basal cell adenoma arising in the parapharyngeal space. On MR imaging, the mass was a wellcircumscribed cystic and solid tumor with a thin fibrous capsule and intratumoral hemorrhage. It was confined to the parapharyngeal space, separating from the deep lobe of the parotid gland. The solid portion of the tumor was slightly hypointense/hyperintense to the muscle on T1-/T2-weighted images and was relatively well enhanced on Gd-enhanced T1-weighted images. The cystic contents of the mass were hyperintense on both T1- and T2-weighted images and were proven to be a hemorrhage. D 2001 Elsevier Science Inc. All rights reserved. Keywords: MR, head and neck; MR, parapharyngeal space; MR, salivary gland; Basal cell adenoma, head and neck
1. Introduction Basal cell adenoma is a rare benign neoplasm of the salivary gland origin that derives its name from the basaloid appearance of the tumor cells. It occurs most frequently in the parotid gland, less commonly in the minor salivary glands of the upper lip, and uncommonly in the oral cavity, lower lip, hard palate, and submandibular gland [1 –3]. In the English literature, there have been no reports of basal cell adenoma occurring in the parapharyngeal space. We describe the MR findings of a patient with parapharyngeal basal cell adenoma.
2. Case report A 61-year-old woman was admitted with the complaint of a 7-year history of a bulging mass in the left oral cavity. She had had a fine needle aspiration biopsy at another
* Corresponding author. Tel.: +82-2-2224-4400; fax: +82-2-476-4719. E-mail address: [email protected] (H.K. Lee).
hospital 1 month previously. Microscopic examination at that hospital led to the diagnosis of a benign cyst. At the other hospital, a neck CT had been performed. A large well-circumscribed cystic and solid mass was found in the left parapharyngeal space and showed the heterogeneous, strong enhancement on contrast-enhanced CT scans (not shown). The preferred imaging diagnosis was schwannoma. One month later, an MR examination was performed at our hospital. On MR images, a well-encapsulated, round mass was found in the left parapharyngeal space, thereby obliterating the fat of the parapharyngeal space with partly peripheral displacement. The mass was composed of a central solid portion and a peripheral cystic portion with a thin rim. The solid portion was slightly hypointense on T1-weighted images and hyperintense to the muscle on T2-weighted images, which contained small hemorrhagic components (Fig. 1A,B). There was also relatively good enhancement on gadolinium-enhanced T1-weighted images (Fig. 1C). Cystic fluid was hyperintense on both T1- and T2-weighted images and was proven at surgery to be a hemorrhage (Fig. 1A,B). The capsule of the mass showed a hypointense, smooth thin rim on all MR sequences. The
0899-7071/01/$ – see front matter D 2001 Elsevier Science Inc. All rights reserved. PII: S 0 8 9 9 - 7 0 7 1 ( 0 1 ) 0 0 3 4 0 - 0
A.K. Jeong et al. / Journal of Clinical Imaging 25 (2001) 392–395
393
Fig. 1. A 61-year-old woman with a bulging mass in the left oral cavity. (A) Axial T1-weighted (450/12) MR image shows a well-marginated cystic and solid mass in the left parapharyngeal space (arrows). The mass obliterates the parapharyngeal fat and displaces the pharyngeal mucosal space medially, the internal carotid artery posterolaterally, and the longus colli muscle posteriorly. The central solid portion of the mass is slightly hypointense to the muscle and the peripheral cystic contents of the mass are hyperintense. The peripheral cystic contents was proven to be a hemorrhage. The capsule of the mass showed a hypointense, thin rim. The mass was separated from the deep lobe of the parotid gland by a fat plane. (B) Axial T2-weighted (3700/99) MR image at the same level A shows that the solid portion of the mass is relatively hyperintense to the muscle and the cystic contents are also hyperintense with a hypointense thin rim. (C) Contrast-enhanced axial T1-weighted (450/12) MR image at the same level, reveals good enhancement of the central solid portion, but only subtle enhancement of the peripheral rim. (D) Contrast-enhanced coronal T1-weighted (450/12) MR image shows that the mass occupies the left parapharyngeal space of the naso- and oropharyx (arrows) and has a hypointense rim. (E) Photomicrograph of the parapharyngeal mass (magnification 200, hematoxylin – eosin stain). The solid and trabecular tumor is composed of larger, lighter stained basaloid cells and peripherally located, palisading cells with small basophilic nuclei and scanty cytoplasm. (F) Gross findings of the parapharyngeal mass indicate that the cut surface of the mass is well-encapsulated, partly cystic, and solid. The solid portion is homogeneously yellowish white and myxoid on the cut surface. Hemosiderin is deposited along the peripheral rim and cystic walls.
394
A.K. Jeong et al. / Journal of Clinical Imaging 25 (2001) 392–395
Fig. 1. (continued )
mass was separated from the deep lobe of the parotid gland by a fat plane, which displaced the pharyngeal mucosal space medially, the carotid sheath posterolaterally, the deep lobe of the parotid gland laterally, and the longus colli muscle posteriorly. On coronal images, the mass was confined to the left parapharyngeal space of the nasopharynx and oropharyx levels (Fig. 1D). There were no abnormal lymph nodes in either neck area. Excision of the mass was performed via a cervical approach below the mandible. The cut surface of the specimen was cystic and solid. The solid portion was yellowish white and myxoid with a central hemorrhagic component (Fig. 1F). Microscopic examination revealed interanastomosing trabeculae and tubules of monotonous basaloid cells in the cellular stroma composing the solid portion. The cystic spaces were lined with attenuated thin epithelium and contained some proteinaceous material. The cyst wall showed dense collagenous fibrous tissue with multifocal calcification, fresh hemorrhage, and hemosiderin-laden macrophages. The histopathologic diagnosis of basal cell adenoma was made (Fig. 1E), and the tumor was thought to have originated in the minor salivary gland in the parapharyngeal space.
3. Discussion Salivary gland tumors comprise less than 3% of all neoplasms of the head and neck. Basal cell adenoma is one of the rare, benign salivary gland neoplasms, accounting for only 2% of all tumors arising from the salivary glands [4]. Basal cell adenoma was once included in the category of monomorphic adenomas, which is an obsolete term. How-
ever, according to the 1991 classification of the World Health Organization, it is recommended to classify benign salivary tumors, other than pleomorphic adenomas, into several specific types, among them basal cell adenoma [3]. There is a nearly equal occurrence between males and females [5]. This tumor can occur at any age but occurs most often in middle-aged and older adults, with its peak occurrence during the seventh decade of life. Local excision of basal cell adenoma has been curative. Although recurrence is rare, the membranous subtype, which is a hereditary variety of basal cell adenoma, has been reported to have a 25 – 37% recurrence rate on some pathologic reports. Malignant transformation to basal cell adenocarcinoma is rare but has been suggested by some researchers [6]. The parapharyngeal space contains mainly fatty tissue, lymphatics, and minor salivary gland tissue, and is actually a potential space located lateral to the upper pharynx and extends from the skull base to the hyoid bone. This space may be the source of salivary gland tumors, as it was in this case [7]. The common clinical presentation of basal cell adenoma is a slow-growing, asymptomatic, freely movable mass [1,8]. Therefore, a deep-seated tumor can become a large mass before it becomes symptomatic. Microscopically, basal cell adenoma is characteristically composed of small isomorphic epithelial cells without myoepithelial cells or myxochondroid elements, as is typically seen in pleomorphic adenoma. This tumor is usually encapsulated by fibrous connective tissue with the cell masses separated by a thin cobweb-like stroma. This explains the low signal intensity of the tumor capsule on T2-weighted images, as was seen in this case. The growth patterns vary from solid or trabecular to tubular or canalicular [9].
A.K. Jeong et al. / Journal of Clinical Imaging 25 (2001) 392–395
Grossly, basal cell adenoma is solid or cystic, or gray or white and does not usually show intratumoral hemorrhage. In these characteristics, it is similar to pleomorphic adenoma. However, Triest et al. [3] reported that basal cell adenoma shows a characteristic vascular pattern in which small capillaries and venules are prominent in the microcystic areas of the adenoma. These vascular structures can cause intratumoral hemorrhage, as was seen in this case. The MR differential diagnosis for parapharyngeal tumors includes other tumors of minor salivary gland origin, nerve sheath tumors, and paragangliomas. Pleomorphic adenoma of a minor salivary gland tumor is the most common primary lesion arising in the parapharyngeal space. On MR images, it usually has heterogeneous intermediate signal intensity on T1-weighted images and intermediate to high signal intensity on T2-weighted images. Pleomorphic adenoma often shows cystic change. On MR images, it is difficult to make a differential diagnosis from the other parapharyngeal mass. It also displaces the carotid sheath posteriorly [10]. Schwannoma is usually located in the carotid space, therefore, it displaces the internal carotid artery anteromedially. It usually has heterogeneous signal intensity due to cystic change as well as hemorrhage, but it has strong enhancement on MR images. Paraganglioma usually displaces the internal carotid artery anteriorly because of its origin around the vagus
395
nerve in the carotid space. This hypervascular tumor has multiple focal and serpentine areas of low signal intensity representing vascular flow voids within the mass.
References [1] Neville BW, Damm DD, Allen CM, Bouquot JE. Salivary gland pathology. Oral and maxillofacial pathology. Philadelphia (PA): Saunders, 1995. p. 347. [2] Yamazaki T, Kotani A, Kawakami T. Basal cell adenoma of the sublingual gland. J Oral Maxillofac Surg 1987;45:270 – 3. [3] Triest WE, Fried MP, Stanievich JF. Membranous basal cell adenoma of the hypopharynx. Arch Otolaryngol 1983;109:774 – 7. [4] Mintz GA, Abrams AM, Melrose RJ. Monomorphic adenoma of the major and minor salivary glands. Oral Surg, Oral Med, Oral Pathol 1982;53:375. [5] Oslen KD. Tumors and surgery of the parapharyngeal space. Laryngoscope 1994;104:1 – 28. [6] Leegaard T, Lindeman H. Salivary gland tumors: clinical picture and treatment. Acta Otolaryngol 1970;263:155. [7] Ferreiro JA. Immunohistochemistry of basal cell adenoma of the major salivary glands. Histopathology 1994;24:539. [8] Esteves ARF, Dib LL, Carvalho LV. Basal cell adenoma: a case report. J Oral Maxillofac Surg 1997;55:1323 – 5. [9] Weiner AP. Monomorphic adenoma, canalicular variant. J Oral Surg 1977;35:414 – 5. [10] Som PM, Sacher M, Stollman AL, Biller HF, Lawson W. Common tumors of the parapharyngeal space: refined imaging diagnosis. Radiology 1988;169(1):81 – 5.