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Squamous cell carcinoma originating in the parotid gland: MRI features with histopathological correlation
Clinical Radiology 69 (2014) 41e44
Contents lists available at SciVerse ScienceDirect
Clinical Radiology journal homepage: www.clinicalradiologyonline.net
Squamous cell carcinoma originating in the parotid gland: MRI features with histopathological correlation H. Takahashi a, *, N. Kashiwagi a, T. Chikugo b, K. Nakanishi c, Y. Tomita d, T. Murakami a a
Department of Radiology, Kinki University, Faculty of Medicine, Osaka-Sayama, Japan Department of Pathology, Kinki University, Faculty of Medicine, Osaka-Sayama, Japan c Department of Diagnostic Radiology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan d Department of Pathology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan b
art icl e i nformat ion Article history: Received 26 February 2013 Received in revised form 30 July 2013 Accepted 6 August 2013
AIM: To report the magnetic resonance imaging (MRI) and corresponding histopathological features of squamous cell carcinoma (SCC) originating in the parotid gland. MATERIALS AND METHODS: The MRI images of seven patients with histopathologically proven SCC originating in the parotid gland were reviewed retrospectively, with an emphasis on tumour size, shape, contour definition, extraparotid infiltration, signal characteristics, and the presence of central necrosis. These were correlated with the microscopic findings of the surgical specimens. RESULTS: The tumours ranged in size from 3.9e7 cm (mean 4.7 cm). All tumours had an illdefined margin with extraparotid infiltration, which seemed to reflect the invasive growth of the tumour cells on histopathological examination. The solid portions of the tumours showed predominantly low to intermediate signal intensities on T2-weighted images, which seemed to reflect the high cellularity, intercellular bridges, and/or keratin pearl formation observed at histopathological examination. Five of the seven tumours had central necrosis. CONCLUSION: A relatively large tumour with central necrosis is a useful imaging feature of SCCs originating in the parotid gland, in addition to the well-recognized indicators of parotid malignancy, such as an ill-defined margin, extraparotid infiltration, and low to intermediate signal intensity on T2-weighted images. Ó 2013 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction Squamous cell carcinoma (SCC) originating in the parotid gland is a high-grade malignant tumour and comprises about 0.1e3.4% of all parotid gland tumours.1e4 Because
their incidence is low, there has been no report of the imaging features of these tumours. The aim of the present study was to report the magnetic resonance imaging (MRI) and corresponding histopathological features of SCCs originating in the parotid glands of seven patients.
Materials and methods * Guarantor and correspondent: H. Takahashi, 377-2 Ohno-Higashi, Osaka-Sayama 589-8511, Japan. Tel./fax: þ81 72 366 0221. E-mail address: [email protected] (H. Takahashi).
The clinical records and MRI images of seven patients diagnosed with histologically proven SCC of the parotid
0009-9260/$ e see front matter Ó 2013 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.crad.2013.08.002
42
H. Takahashi et al. / Clinical Radiology 69 (2014) 41e44
Results
gland at (Kinki University and Osaka Medical Center for Cancer and Cardiovascular diseases) over the past 10 years were reviewed. The patients included five men and two women (age range 35e82 years; average age 63 years). All patients underwent surgical resection and were diagnosed with SCC originating in the parotid gland after careful clinical examination and preoperative total-body imaging test that excluded metastasis from other sites. MRI was performed before surgical resection in all patients, using a 1.5 T MRI unit in five patients and a 3 T MRI unit in two patients. Spin-echo (SE) T1-weighted axial MRI images, SE T2-weighted axial images, and contrast-enhanced T1weighted axial and coronal images with the fatsuppression technique were obtained for all patients. Two neuroradiologists reviewed all MRI images to draw consensus conclusions, with an emphasis on the tumour size, shape, contour definition, extraparotid infiltration, signal characteristics, and the presence of central necrosis. The tumour size was measured as the maximal diameter on a cross-sectional image. The tumour shape was classified as round, lobulate, or irregular. Its contour was classified as well-defined or ill-defined on contrast-enhanced T1weighted images with the fat-suppression technique. The signal intensity was assessed for the solid portion of the internal tumour contents on T2-weighted images and classified as low, intermediate, or high. The signal intensities for the musculature and cerebrospinal fluid (CSF) were used as the intensity standards. Low signal intensity was defined as lower signal than that of the musculature. Intermediate signal intensity was defined as equivalent or higher signal than that of the musculature and lower signal than that of CSF. High signal intensity was defined as equivalent or higher signal than that of the CSF. Central necrosis was defined as a central area of high signal intensity in the tumour on T2-weighted images with no contrast enhancement. All histopathological examinations were performed with haematoxylin and eosin staining. An experienced radiologist and histopathologist correlated the MRI features with the histopathology specimens in all cases.
The clinical records and MRI features of the patients are summarized in Table 1. Representative cases are shown in Figs 1 and 2. Five tumours were de novo carcinomas and two were malignant derivatives of pleomorphic adenomas. Six patients presented with a swelling of the cheek, accompanied by pain in two patients and by facial palsy in three patients. The parotid gland tumour of one asymptomatic patient was incidentally detected during a cancer-screening test by positron-emission tomographyecomputed tomography. The tumours ranged in size from 3.9e7 cm (mean 4.7 cm). Six tumours were irregularly shaped and the other was lobulate. All the tumours had an ill-defined margin along the entire circumference, with extraparotid infiltration. These features correlated histopathologically with the infiltrative growth of the tumour cells, which extended beyond the capsule of the parotid gland. The signal intensities of the solid portions of five tumours were loweintermediate or intermediate on T2weighted image, and intermediateehigh in the other two tumours. The areas of low or intermediate signal intensity on T2-weighted images correlated histopathologically with high cellular proliferation, with intercellular bridges, and/or keratin pearl formation. Five of the tumours showed central necrosis, which was microscopically confirmed by histopathological examination to display necrotic changes, such as degenerative tissue and cellular collapse.
Discussion SCC is the predominant histological type of head and neck tumour, although it is rare in the parotid gland. SCC of the parotid gland usually occurs as an intra- or periparotid lymph-node metastasis from a skin malignancy of the face or scalp region.3,4 Therefore, to confirm the diagnosis of SCC originating in the parotid gland, a careful examination including an imaging test must be made to rule out metastatic SCC from another site. SCCs originating in the parotid gland can be divided into two different entities: (1) primary (de novo) SCC and (2) SCC that develops accompanied by a
Table 1 Summary of clinical and magnetic resonance imaging (MRI) features. Case no.
Age/sex
MRI unit (T)
Pattern of SCC occurrence
Symptoms
Size (cm)
Shape
Contour definition
Extraparotid infiltration
Signal characteristics on T2 weighted images
Central necrosis
1
76/M
1.5
De novo
4.2
Irregular
Ill-defined
Yes
Low to intermediate
Yes
2
63/F
3
De novo
3.9
Irregular
Ill-defined
Yes
Intermediate to high
No
3
62/M
3
De novo
4.2
Irregular
Ill-defined
Yes
Intermediate to high
Yes
4
35/M
1.5
5.3
Lobulate
Ill-defined
Yes
Low to intermediate
Yes
5
70/F
1.5
Ex pleomorphic adenoma De novo
7
Irregular
Ill-defined
Yes
Intermediate
Yes
6
55/M
1.5
De novo
4.5
Irregular
Ill-defined
Yes
Low to intermediate
Yes
7
82/M
1.5
Ex pleomorphic adenoma
Painless swelling of left cheek (rapid progress) Asymptomatic (detected at PET-CT screening) Painless swelling of right cheek (rapid progress) Painful swelling of right cheek Facial paralysis Painful swelling of right cheek Facial paralysis Painless swelling of right cheek Painless swelling of left cheek Facial paralysis
4.1
Irregular
Ill-defined
Yes
Low to intermediate
No
PET-CT, positron-emission tomography combined with computed tomography.
H. Takahashi et al. / Clinical Radiology 69 (2014) 41e44
43
Figure 1 A 70-year-old woman with painful swelling of the cheek and facial nerve palsy. MRI images were obtained using the 1.5 T MRI system. (a) Axial T2-weighted image shows that the irregular-shaped mass involving both the superficial and deep parotid lobes contains a central high-signal area (arrow). (b) On an axial, contrast-enhanced T1-weighted image with the fat-suppression technique, the mass has a central unenhanced area (arrow) and infiltrates the subcutaneous fat, mandibular ramus, and parapharyngeal space. (c) Part of the tumour tissue appears as an arc-shaped area on analysis of a histopathological specimen, whereas an empty space, representing the necrotic area, is also visible (*). (d) Histopathological features, including evidence of abundant cytoplasmic keratin pearls (arrows) and intercellular bridges (arrowheads), indicate SCC.
pre-existing pleomorphic adenoma. Carcinoma ex pleomorphic adenoma of the parotid gland is a rare but aggressive malignancy. The malignant component of carcinoma ex pleomorphic adenoma is most often adenocarcinoma, then adenoid cystic carcinoma, mucoepidermoid carcinoma, or salivary duct carcinoma.5 SCC is a less common histological subtype.5 Carcinoma ex pleomorphic adenoma can show the MRI findings, such as co-existence of an invasive parotid mass, which are non-specific and encapsulated component of pleomorphic adenoma.6 In the present series, the imaging features of the five primary tumours and those of the two pleomorphicadenoma-derived tumours did not differ greatly, because the components of the pleomorphic adenomas were too small to influence the overall MRI features. A histopathological examination could confirm the existence of pleomorphic adenoma with the detection of extensive hyalinization, which is known to occur in degenerated pleomorphic adenomas.7
SCC originating in the parotid gland usually occurs in elderly subjects, and presented as a painless neck mass in most of the present patients, with characteristics similar to those of previously reported cases.1e3,8 The frequent occurrence of facial nerve paralysis reflects the aggressive behaviour of this tumour. Although the small number of patients in the present study precluded statistical analysis, the MRI features of the patients showed certain tendencies, such as large tumour size, irregular shape, ill-defined margin, extraparotid infiltration, loweintermediate signal intensity in the solid portions on T2-weighted images, and the presence of central necrosis. Although a previous study reported that lesion size is not a reliable indicator to distinguish pleomorphic adenomas from carcinomas,9,10 the large tumours in the present cohort may reflect the aggressive behaviour of this tumour. Most patients were classified above the T3 stage at presentation, based on the size criterion of the TNM staging system for salivary gland tumours.11 As for the tumour shape, both
44
H. Takahashi et al. / Clinical Radiology 69 (2014) 41e44
Figure 2 A 62-year-old man with painful swelling of the cheek. MRI images were obtained using the 3 T MRI machine. (a) Axial T2-weighted image shows that the irregular-shaped mass involving the deep parotid lobes contains a central high-signal area (arrow). (b) On an axial, contrastenhanced T1-weighted image, the mass has a central unenhanced area (arrow) and infiltrates the parapharyngeal space. (c) Histopathological features include evidence of degenerative tissue and cellular collapse, representing the necrotic area (arrow) adjacent to the tumour cells.
parotid malignancies and pleomorphic adenomas can form irregular masses.9 The ill-defined margins and extraparotid infiltration, which reflect the invasive growth of the tumour cells, are consistent with other reported findings for parotid malignancies.12e14 Loweintermediate signal intensities of the solid portions for the tumours on T2-weighted images are also consistent with high-grade parotid malignancies (e.g., high-grade malignant muco-epidermoid carcinoma and carcinoma ex pleomorphic adenoma) and cervical SCCs in other regions, which have been reported to indicate a lack of serous and mucinous products or high cell densities.12e15 Keratin deposition, which is a histological characteristic of SCCs, also presents as low to intermediate signal intensities on T2-weighted images.16 The appearances of SCC originating in the parotid gland on MRI can be similar to other more common parotid malignancies (e.g., adenoid cystic carcinoma and muco-epidermoid carcinoma)17; however, the prognosis of parotid SCC appears to be poor with a 5year survival rate approximately 30% or less, which is important when considering SCC in the differential diagnosis of parotid malignancies.1,2 Previous reports that have described the MRI features of parotid tumours have not paid particular attention to central necrosis. Large cervical SCCs arising as either primary tumours or metastatic lymph nodes tend to develop necrosis, which can often be observed on MRI images.18,19 The observation of frequent central necrosis in the present study is a feature shared with other cervical SCCs. In conclusion, a relatively large tumour with central necrosis is a useful imaging feature of SCCs originating in the parotid gland, in addition to the well-recognized indicators of parotid malignancy, such as an ill-defined margin, extraparotid infiltration, and low to intermediate signal intensity on T2-weighted images.
References 1. Flynn MB, Maguire S, Martinez S, et al. Primary squamous cell carcinoma of the parotid gland: the importance of correct histological diagnosis. Ann Surg Oncol 1999;6:768e70.
2. Batsakis JG, McClatchey KD, Johns M, et al. Primary squamous cell carcinoma of the parotid gland. Arch Otolaryngol 1976;102:355e7. 3. Ying YL, Johnson JT, Myers EN. Squamous cell carcinoma of the parotid gland. Head Neck 2006;28:626e32. 4. Taxy JB. Squamous carcinoma in a major salivary gland: a review of the diagnostic considerations. Arch Pathol Lab Med 2001;125:740e5. 5. Antony J, Gopalan V, Smith RA, et al. Carcinoma ex pleomorphic adenoma: a comprehensive review of clinical, pathological and molecular data. Head Neck Pathol 2011;10:1007. 6. Kashiwagi N, Murakami T, Chikugo T, et al. Carcinoma ex pleomorphic adenoma of the parotid gland. Acta Radiol 2012;53:303e6. 7. Olsen KD, Lewis JE. Carcinoma ex pleomorphic adenoma: a clinicopathologic review. Head Neck 2001;23:705e12. 8. Spiro RH, Huvos AG, Strong EW. Cancer of the parotid gland. A clinicopathologic study of 288 primary cases. Am J Surg 1975;130:452e9. 9. Takashima S, Takayama F, Wang Q, et al. Parotid gland lesions: diagnosis of malignancy with MRI and flow cytometric DNA analysis and cytology in fine-needle aspiration biopsy. Head Neck 1999;21:43e51. 10. Joe VQ, Westesson PL. Tumors of the parotid gland: MR imaging characteristics of various histologic types. AJR Am J Roentgenol 1994;163:433e8. 11. American Joint Committee on Cancer. The 7th edition of the American Joint Committee on Cancer TNM staging system for salivary gland tumor. Available at: http://www.cancerstaging.org/ [accessed 12.12.12]. 12. Christe A, Waldherr C, Hallett R, et al. MR imaging of parotid tumors: typical lesion characteristics in MR imaging improve discrimination between benign and malignant disease. AJNR Am J Neuroradiol 2011;32:1202e7. 13. Som PM, Biller HF. High-grade malignancies of the parotid gland: identification with MR imaging. Radiology 1989;173:823e6. 14. Freling NJM, Molenaar WM, Albert V, et al. Malignant parotid tumors: clinical use of MR imaging and histologic correlation. Radiology 1992;185:691e6. 15. Kashiwagi N, Dote K, Kawano K, et al. MRI findings of mucoepidermoid carcinoma of the parotid gland: correlation with pathological features. Br J Radiol 2012;85:709e13. 16. Fukunari F, Okamura K, Zeze R, et al. Cervical lymph nodes with or without metastases from oral squamous carcinoma: a correlation of MRI findings and histopathologic architecture. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:890e9. 17. Bjørndal K, Krogdahl A, Therkildsen MH, et al. Salivary gland carcinoma in Denmark 1990e2005: a national study of incidence, site and histology. Results of the Danish Head and Neck Cancer Group (DAHANCA). Oral Oncol 2011;47:677e82. 18. Fruehwald-Pallamar J, Czerny C, Mayerhoefer ME, et al. Functional imaging in head and neck squamous cell carcinoma: correlation of PET/CT and diffusion-weighted imaging at 3 Tesla. Eur J Nucl Med Mol Imaging 2011;38:1009e19. 19. Zoumalan RA, Kleinberger AJ, Morris LG, et al. Lymph node central necrosis on computed tomography as predictor of extracapsular spread in metastatic head and neck squamous cell carcinoma: pilot study. J Laryngol Otol 2010;124:1284e8.
Contents lists available at SciVerse ScienceDirect
Clinical Radiology journal homepage: www.clinicalradiologyonline.net
Squamous cell carcinoma originating in the parotid gland: MRI features with histopathological correlation H. Takahashi a, *, N. Kashiwagi a, T. Chikugo b, K. Nakanishi c, Y. Tomita d, T. Murakami a a
Department of Radiology, Kinki University, Faculty of Medicine, Osaka-Sayama, Japan Department of Pathology, Kinki University, Faculty of Medicine, Osaka-Sayama, Japan c Department of Diagnostic Radiology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan d Department of Pathology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan b
art icl e i nformat ion Article history: Received 26 February 2013 Received in revised form 30 July 2013 Accepted 6 August 2013
AIM: To report the magnetic resonance imaging (MRI) and corresponding histopathological features of squamous cell carcinoma (SCC) originating in the parotid gland. MATERIALS AND METHODS: The MRI images of seven patients with histopathologically proven SCC originating in the parotid gland were reviewed retrospectively, with an emphasis on tumour size, shape, contour definition, extraparotid infiltration, signal characteristics, and the presence of central necrosis. These were correlated with the microscopic findings of the surgical specimens. RESULTS: The tumours ranged in size from 3.9e7 cm (mean 4.7 cm). All tumours had an illdefined margin with extraparotid infiltration, which seemed to reflect the invasive growth of the tumour cells on histopathological examination. The solid portions of the tumours showed predominantly low to intermediate signal intensities on T2-weighted images, which seemed to reflect the high cellularity, intercellular bridges, and/or keratin pearl formation observed at histopathological examination. Five of the seven tumours had central necrosis. CONCLUSION: A relatively large tumour with central necrosis is a useful imaging feature of SCCs originating in the parotid gland, in addition to the well-recognized indicators of parotid malignancy, such as an ill-defined margin, extraparotid infiltration, and low to intermediate signal intensity on T2-weighted images. Ó 2013 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction Squamous cell carcinoma (SCC) originating in the parotid gland is a high-grade malignant tumour and comprises about 0.1e3.4% of all parotid gland tumours.1e4 Because
their incidence is low, there has been no report of the imaging features of these tumours. The aim of the present study was to report the magnetic resonance imaging (MRI) and corresponding histopathological features of SCCs originating in the parotid glands of seven patients.
Materials and methods * Guarantor and correspondent: H. Takahashi, 377-2 Ohno-Higashi, Osaka-Sayama 589-8511, Japan. Tel./fax: þ81 72 366 0221. E-mail address: [email protected] (H. Takahashi).
The clinical records and MRI images of seven patients diagnosed with histologically proven SCC of the parotid
0009-9260/$ e see front matter Ó 2013 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.crad.2013.08.002
42
H. Takahashi et al. / Clinical Radiology 69 (2014) 41e44
Results
gland at (Kinki University and Osaka Medical Center for Cancer and Cardiovascular diseases) over the past 10 years were reviewed. The patients included five men and two women (age range 35e82 years; average age 63 years). All patients underwent surgical resection and were diagnosed with SCC originating in the parotid gland after careful clinical examination and preoperative total-body imaging test that excluded metastasis from other sites. MRI was performed before surgical resection in all patients, using a 1.5 T MRI unit in five patients and a 3 T MRI unit in two patients. Spin-echo (SE) T1-weighted axial MRI images, SE T2-weighted axial images, and contrast-enhanced T1weighted axial and coronal images with the fatsuppression technique were obtained for all patients. Two neuroradiologists reviewed all MRI images to draw consensus conclusions, with an emphasis on the tumour size, shape, contour definition, extraparotid infiltration, signal characteristics, and the presence of central necrosis. The tumour size was measured as the maximal diameter on a cross-sectional image. The tumour shape was classified as round, lobulate, or irregular. Its contour was classified as well-defined or ill-defined on contrast-enhanced T1weighted images with the fat-suppression technique. The signal intensity was assessed for the solid portion of the internal tumour contents on T2-weighted images and classified as low, intermediate, or high. The signal intensities for the musculature and cerebrospinal fluid (CSF) were used as the intensity standards. Low signal intensity was defined as lower signal than that of the musculature. Intermediate signal intensity was defined as equivalent or higher signal than that of the musculature and lower signal than that of CSF. High signal intensity was defined as equivalent or higher signal than that of the CSF. Central necrosis was defined as a central area of high signal intensity in the tumour on T2-weighted images with no contrast enhancement. All histopathological examinations were performed with haematoxylin and eosin staining. An experienced radiologist and histopathologist correlated the MRI features with the histopathology specimens in all cases.
The clinical records and MRI features of the patients are summarized in Table 1. Representative cases are shown in Figs 1 and 2. Five tumours were de novo carcinomas and two were malignant derivatives of pleomorphic adenomas. Six patients presented with a swelling of the cheek, accompanied by pain in two patients and by facial palsy in three patients. The parotid gland tumour of one asymptomatic patient was incidentally detected during a cancer-screening test by positron-emission tomographyecomputed tomography. The tumours ranged in size from 3.9e7 cm (mean 4.7 cm). Six tumours were irregularly shaped and the other was lobulate. All the tumours had an ill-defined margin along the entire circumference, with extraparotid infiltration. These features correlated histopathologically with the infiltrative growth of the tumour cells, which extended beyond the capsule of the parotid gland. The signal intensities of the solid portions of five tumours were loweintermediate or intermediate on T2weighted image, and intermediateehigh in the other two tumours. The areas of low or intermediate signal intensity on T2-weighted images correlated histopathologically with high cellular proliferation, with intercellular bridges, and/or keratin pearl formation. Five of the tumours showed central necrosis, which was microscopically confirmed by histopathological examination to display necrotic changes, such as degenerative tissue and cellular collapse.
Discussion SCC is the predominant histological type of head and neck tumour, although it is rare in the parotid gland. SCC of the parotid gland usually occurs as an intra- or periparotid lymph-node metastasis from a skin malignancy of the face or scalp region.3,4 Therefore, to confirm the diagnosis of SCC originating in the parotid gland, a careful examination including an imaging test must be made to rule out metastatic SCC from another site. SCCs originating in the parotid gland can be divided into two different entities: (1) primary (de novo) SCC and (2) SCC that develops accompanied by a
Table 1 Summary of clinical and magnetic resonance imaging (MRI) features. Case no.
Age/sex
MRI unit (T)
Pattern of SCC occurrence
Symptoms
Size (cm)
Shape
Contour definition
Extraparotid infiltration
Signal characteristics on T2 weighted images
Central necrosis
1
76/M
1.5
De novo
4.2
Irregular
Ill-defined
Yes
Low to intermediate
Yes
2
63/F
3
De novo
3.9
Irregular
Ill-defined
Yes
Intermediate to high
No
3
62/M
3
De novo
4.2
Irregular
Ill-defined
Yes
Intermediate to high
Yes
4
35/M
1.5
5.3
Lobulate
Ill-defined
Yes
Low to intermediate
Yes
5
70/F
1.5
Ex pleomorphic adenoma De novo
7
Irregular
Ill-defined
Yes
Intermediate
Yes
6
55/M
1.5
De novo
4.5
Irregular
Ill-defined
Yes
Low to intermediate
Yes
7
82/M
1.5
Ex pleomorphic adenoma
Painless swelling of left cheek (rapid progress) Asymptomatic (detected at PET-CT screening) Painless swelling of right cheek (rapid progress) Painful swelling of right cheek Facial paralysis Painful swelling of right cheek Facial paralysis Painless swelling of right cheek Painless swelling of left cheek Facial paralysis
4.1
Irregular
Ill-defined
Yes
Low to intermediate
No
PET-CT, positron-emission tomography combined with computed tomography.
H. Takahashi et al. / Clinical Radiology 69 (2014) 41e44
43
Figure 1 A 70-year-old woman with painful swelling of the cheek and facial nerve palsy. MRI images were obtained using the 1.5 T MRI system. (a) Axial T2-weighted image shows that the irregular-shaped mass involving both the superficial and deep parotid lobes contains a central high-signal area (arrow). (b) On an axial, contrast-enhanced T1-weighted image with the fat-suppression technique, the mass has a central unenhanced area (arrow) and infiltrates the subcutaneous fat, mandibular ramus, and parapharyngeal space. (c) Part of the tumour tissue appears as an arc-shaped area on analysis of a histopathological specimen, whereas an empty space, representing the necrotic area, is also visible (*). (d) Histopathological features, including evidence of abundant cytoplasmic keratin pearls (arrows) and intercellular bridges (arrowheads), indicate SCC.
pre-existing pleomorphic adenoma. Carcinoma ex pleomorphic adenoma of the parotid gland is a rare but aggressive malignancy. The malignant component of carcinoma ex pleomorphic adenoma is most often adenocarcinoma, then adenoid cystic carcinoma, mucoepidermoid carcinoma, or salivary duct carcinoma.5 SCC is a less common histological subtype.5 Carcinoma ex pleomorphic adenoma can show the MRI findings, such as co-existence of an invasive parotid mass, which are non-specific and encapsulated component of pleomorphic adenoma.6 In the present series, the imaging features of the five primary tumours and those of the two pleomorphicadenoma-derived tumours did not differ greatly, because the components of the pleomorphic adenomas were too small to influence the overall MRI features. A histopathological examination could confirm the existence of pleomorphic adenoma with the detection of extensive hyalinization, which is known to occur in degenerated pleomorphic adenomas.7
SCC originating in the parotid gland usually occurs in elderly subjects, and presented as a painless neck mass in most of the present patients, with characteristics similar to those of previously reported cases.1e3,8 The frequent occurrence of facial nerve paralysis reflects the aggressive behaviour of this tumour. Although the small number of patients in the present study precluded statistical analysis, the MRI features of the patients showed certain tendencies, such as large tumour size, irregular shape, ill-defined margin, extraparotid infiltration, loweintermediate signal intensity in the solid portions on T2-weighted images, and the presence of central necrosis. Although a previous study reported that lesion size is not a reliable indicator to distinguish pleomorphic adenomas from carcinomas,9,10 the large tumours in the present cohort may reflect the aggressive behaviour of this tumour. Most patients were classified above the T3 stage at presentation, based on the size criterion of the TNM staging system for salivary gland tumours.11 As for the tumour shape, both
44
H. Takahashi et al. / Clinical Radiology 69 (2014) 41e44
Figure 2 A 62-year-old man with painful swelling of the cheek. MRI images were obtained using the 3 T MRI machine. (a) Axial T2-weighted image shows that the irregular-shaped mass involving the deep parotid lobes contains a central high-signal area (arrow). (b) On an axial, contrastenhanced T1-weighted image, the mass has a central unenhanced area (arrow) and infiltrates the parapharyngeal space. (c) Histopathological features include evidence of degenerative tissue and cellular collapse, representing the necrotic area (arrow) adjacent to the tumour cells.
parotid malignancies and pleomorphic adenomas can form irregular masses.9 The ill-defined margins and extraparotid infiltration, which reflect the invasive growth of the tumour cells, are consistent with other reported findings for parotid malignancies.12e14 Loweintermediate signal intensities of the solid portions for the tumours on T2-weighted images are also consistent with high-grade parotid malignancies (e.g., high-grade malignant muco-epidermoid carcinoma and carcinoma ex pleomorphic adenoma) and cervical SCCs in other regions, which have been reported to indicate a lack of serous and mucinous products or high cell densities.12e15 Keratin deposition, which is a histological characteristic of SCCs, also presents as low to intermediate signal intensities on T2-weighted images.16 The appearances of SCC originating in the parotid gland on MRI can be similar to other more common parotid malignancies (e.g., adenoid cystic carcinoma and muco-epidermoid carcinoma)17; however, the prognosis of parotid SCC appears to be poor with a 5year survival rate approximately 30% or less, which is important when considering SCC in the differential diagnosis of parotid malignancies.1,2 Previous reports that have described the MRI features of parotid tumours have not paid particular attention to central necrosis. Large cervical SCCs arising as either primary tumours or metastatic lymph nodes tend to develop necrosis, which can often be observed on MRI images.18,19 The observation of frequent central necrosis in the present study is a feature shared with other cervical SCCs. In conclusion, a relatively large tumour with central necrosis is a useful imaging feature of SCCs originating in the parotid gland, in addition to the well-recognized indicators of parotid malignancy, such as an ill-defined margin, extraparotid infiltration, and low to intermediate signal intensity on T2-weighted images.
References 1. Flynn MB, Maguire S, Martinez S, et al. Primary squamous cell carcinoma of the parotid gland: the importance of correct histological diagnosis. Ann Surg Oncol 1999;6:768e70.
2. Batsakis JG, McClatchey KD, Johns M, et al. Primary squamous cell carcinoma of the parotid gland. Arch Otolaryngol 1976;102:355e7. 3. Ying YL, Johnson JT, Myers EN. Squamous cell carcinoma of the parotid gland. Head Neck 2006;28:626e32. 4. Taxy JB. Squamous carcinoma in a major salivary gland: a review of the diagnostic considerations. Arch Pathol Lab Med 2001;125:740e5. 5. Antony J, Gopalan V, Smith RA, et al. Carcinoma ex pleomorphic adenoma: a comprehensive review of clinical, pathological and molecular data. Head Neck Pathol 2011;10:1007. 6. Kashiwagi N, Murakami T, Chikugo T, et al. Carcinoma ex pleomorphic adenoma of the parotid gland. Acta Radiol 2012;53:303e6. 7. Olsen KD, Lewis JE. Carcinoma ex pleomorphic adenoma: a clinicopathologic review. Head Neck 2001;23:705e12. 8. Spiro RH, Huvos AG, Strong EW. Cancer of the parotid gland. A clinicopathologic study of 288 primary cases. Am J Surg 1975;130:452e9. 9. Takashima S, Takayama F, Wang Q, et al. Parotid gland lesions: diagnosis of malignancy with MRI and flow cytometric DNA analysis and cytology in fine-needle aspiration biopsy. Head Neck 1999;21:43e51. 10. Joe VQ, Westesson PL. Tumors of the parotid gland: MR imaging characteristics of various histologic types. AJR Am J Roentgenol 1994;163:433e8. 11. American Joint Committee on Cancer. The 7th edition of the American Joint Committee on Cancer TNM staging system for salivary gland tumor. Available at: http://www.cancerstaging.org/ [accessed 12.12.12]. 12. Christe A, Waldherr C, Hallett R, et al. MR imaging of parotid tumors: typical lesion characteristics in MR imaging improve discrimination between benign and malignant disease. AJNR Am J Neuroradiol 2011;32:1202e7. 13. Som PM, Biller HF. High-grade malignancies of the parotid gland: identification with MR imaging. Radiology 1989;173:823e6. 14. Freling NJM, Molenaar WM, Albert V, et al. Malignant parotid tumors: clinical use of MR imaging and histologic correlation. Radiology 1992;185:691e6. 15. Kashiwagi N, Dote K, Kawano K, et al. MRI findings of mucoepidermoid carcinoma of the parotid gland: correlation with pathological features. Br J Radiol 2012;85:709e13. 16. Fukunari F, Okamura K, Zeze R, et al. Cervical lymph nodes with or without metastases from oral squamous carcinoma: a correlation of MRI findings and histopathologic architecture. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:890e9. 17. Bjørndal K, Krogdahl A, Therkildsen MH, et al. Salivary gland carcinoma in Denmark 1990e2005: a national study of incidence, site and histology. Results of the Danish Head and Neck Cancer Group (DAHANCA). Oral Oncol 2011;47:677e82. 18. Fruehwald-Pallamar J, Czerny C, Mayerhoefer ME, et al. Functional imaging in head and neck squamous cell carcinoma: correlation of PET/CT and diffusion-weighted imaging at 3 Tesla. Eur J Nucl Med Mol Imaging 2011;38:1009e19. 19. Zoumalan RA, Kleinberger AJ, Morris LG, et al. Lymph node central necrosis on computed tomography as predictor of extracapsular spread in metastatic head and neck squamous cell carcinoma: pilot study. J Laryngol Otol 2010;124:1284e8.