- Email: [email protected]
Differential Diagnosis in Sinonasal Disease
Differential Diagnosis in Sinonasal Disease Gitta Madani, FRCR,* and Timothy J. Beale, FRCR, FRCS† This article summarizes the imaging features that aid in distinguishing inflammatory from neoplastic disease and benign from malignant conditions. Diagnostic pitfalls are highlighted. Semin Ultrasound CT MRI 30:39-45 © 2009 Elsevier Inc. All rights reserved.
I
nflammatory sinonasal disease is ubiquitous, whereas benign and malignant sinonasal tumors are uncommon. The clinical presentation of sinonasal pathology is nonspecific, including facial pain, purulent nasal discharge, epistaxis, and nasal obstruction. A key role of imaging is to distinguish inflammatory, benign, and malignant disease. This article highlights features that aid differential diagnosis.
Diagnostic Clues and Pitfalls Computed tomographic (CT) imaging of the sinonasal cavity is commonly performed; the main indications are in recurrent disease, disease unresponsive to medical treatment, and unilateral symptoms and to provide a roadmap for functional endoscopic surgery. By far, the most common finding is polypoid mucosal thickening due to inflammatory disease or sinonasal polyposis. The radiological features that should alert the radiologist to the possibility of malignancy are as follows: ● ● ● ● ●
Unilateral sinus disease Bony involvement Extensive soft-tissue mass Tumor necrosis Lymphadenopathy
Unilateral Sinus Disease Unilateral sinus disease raises the suspicion of benign or malignant neoplasia (Fig. 1). Early malignancy commonly mimics polypoid mucosal thickening on CT and the unilaterality of the changes may be the only imaging clue.1 A retrospective review of 1118 CT scans of the paranasal sinuses identified
*Imperial College NHS Trust, St. Mary’s Hospital, London, UK. †University College Hospital London, London, UK. Address reprint requests to: Timothy J. Beale, FRCR, FRCS, University College Hospital London, 235 Euston Road, London NW1 2BU, UK. E-mail: [email protected]
0887-2171/09/$-see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1053/j.sult.2008.10.014
28 cases of unilateral sinus disease of which 12 cases were due to neoplasia (6 malignant).2
Bony Involvement There are four patterns of bony involvement in sinonasal disease. Bony erosion is highly suspicious of malignancy and is the typical pattern of involvement in squamous cell carcinoma (Fig. 2A) but may also be observed in inflammatory conditions.3 In particular, inflammation involving the bones of the skull base frequently mimics malignancy.4,5 Bony remodeling, which is more typical of inflammatory conditions such as mucoceles, is also seen in less aggressive malignancies such as olfactory neuroblastoma (Fig. 2B) and benign tumors. Reactive sclerosis is the hallmark of chronic inflammation (Fig. 2C). New bone formation is a feature of chondrosarcoma and osteosarcoma. Wegener’s granulomatosis, fungal infections such as mucormycosis, and reparative granuloma (Fig. 3) frequently have aggressive imaging appearances and mimic malignancy. The coexistence of bony erosion and sclerosis is characteristic of Wegener’s granulomatosis but may also be observed in fungal infections (Fig. 4), adenoid cystic carcinoma, as well as cases where chronic infection is superimposed on malignancy.6 Other benign lesions that may mimic malignancy by causing bony erosion include Brown’s tumor of hyperparathyroidism (Fig. 5), inverted papillomas, and ameloblastoma. New bone formation may be in the form of stippled “chondroid” calcification, which occurs in well-differentiated chondrosarcoma; these calcified foci have low T1-weighted (T1W) and high T2W signal on magnetic resonance imaging (MRI). A sunburst periosteal reaction is highly suspicious of osteosarcoma but a soft-tissue mass causing bony destruction and containing areas of sclerosis (due to matrix mineralization) is a more common finding. Fibrous dysplasia and Paget’s disease have variable MRI appearances depending on the degree of sclerosis, cystic components, and marrow replacement. Both conditions 39
40
G. Madani and T.J. Beale
Figure 1 Unilateral sinus disease. (A) Coronal CT and (B) T2W coronal MRI demonstrating unilateral sinus disease. This is suspicious for neoplastic disease. In this case, an inverted papilloma obstructing the maxillary ostium (arrow) resulted in intermediate signal desiccated antral secretions.
Figure 2 Different types of bone involvement. (A) Coronal CT shows bone erosion and destruction of the bone margins (arrows) by an aggressive malignancy. (B) Coronal CT demonstrates benign bone expansion and remodeling (arrow) in a case of olfactory neuroblastoma. (C) Axial CT image shows reactive bone sclerosis typical of chronic inflammatory disease (arrow).
Differential diagnosis in sinonasal disease
41
Figure 3 Reparative granuloma. (A) Axial and (B) coronal CT images show an expansile and destructive mass centered on left posterior ethmoid and sphenoid sinuses, which was histologically proven to be a reparative granuloma.
cause bone expansion, may enhance avidly, and are easily confused with tumor on MRI but are confidently diagnosed on CT.
Soft-Tissue Abnormalities The majority of sinonasal tumors are of low to intermediate signal intensity on all MRI sequences (Fig. 6); areas of signal heterogeneity may arise due to hemorrhage and necrosis (Fig. 7). Hemorrhage may result in foci of high T1W signal but the T2W signal intensity of blood products is usually low. Thus T2W sequences are usually superior in distinguishing tumor
from inflammatory disease.7 Minor salivary gland tumors present a potential diagnostic pitfall as they may be T2 hyperintense depending on their mucin content and cellularity.7 On MRI, chondrosarcoma, particularly small foci of recurrent disease, may mimic inflammatory disease as they are typically T1 hypointense and T2 hyperintense (Fig. 8). The potential coexistence of inflammatory and malignant disease presents a further diagnostic challenge. Chronic inflammation results in a variety of signal intensities on all sequences due to the absorption of free water by hydrophilic mucoproteins and may therefore mimic malignancy. However, contrast enhancement usually allows the differentiation
Figure 4 Fungal sinusitis (A) axial and (B) coronal CT scans. There is extensive bone remodeling with sinus expansion and bone thinning. The high density within the sinuses is suggestive of fungal infection.
42
Figure 5 Brown tumor. (A) Coronal CT scan. The expansile and destructive mass eroding through the lateral and medial walls of the left maxillary antrum is a brown tumor of hyperparathyroidism and may easily be mistaken for malignancy. (B) Plain film radiograph shows the classic subperiosteal bone resorption on the radial aspect of the middle phalanges.
Figure 6 Typical MRI features of sinonasal tumors. (A) Axial T1W MRI and (B) axial fat saturation T1W gadolinium-enhanced MRI demonstrate an intermediate signal intensity and moderately enhancing mass, extending from the ethmoid sinus into the right anterior sphenoid (white arrows) and left cavernous sinus (black arrows). (C) Axial T2W MRI differentiates the intermediate signal intensity tumor (white stars) from the high signal inflammatory secretions (black stars) in the remaining sphenoid and ethmoidal cells. This tumor is an adenocarcinoma, although its radiological features are nonspecific.
G. Madani and T.J. Beale
Differential diagnosis in sinonasal disease
43
Figure 7 Tumor necrosis. (A) Axial CT and (B) axial T1W MRI demonstrating an advanced squamous cell carcinoma of the maxillary antrum. Note the erosion of the anterior, posterior, and medial walls of the antrum (arrows), demonstrated on both modalities. The tumor contains a central area of necrosis (star).
of moderately enhancing tumor from the bright peripheral enhancement of inflammation and nonenhancement of retained secretions (Fig. 6).8,9 Furthermore, inflammatory sinonasal disease enhances more avidly than malignancy.7 Malignant tumors may exhibit homogeneous or heterogeneous enhancement with complete failure of enhancement of areas of necrosis (Fig. 7). Occasionally, tumors of salivary origin such as adenoid cystic carcinoma show high signal intensity on T2W images, potentially mimicking inflammatory disease, but are usually
distinguishable from inflammatory disease by their enhancement characteristics. Malignant tumors may exhibit homogeneous or heterogeneous enhancement with failure of enhancement of areas of necrosis. There are a few features that raise the possibility of a specific histological subtype. Peripheral areas of cystic degeneration and calcific foci are features associated with olfactory neuroblastoma (esthesioblastoma) but only occur in the minority of cases. Malignant melanoma may be hyperintense on T1W (due to hemorrhage and the paramagnetic effect of
Figure 8 Chondrosarcoma on MRI (A) and (B) axial and sagittal T1W gadolinium-enhanced images, demonstrating the typical MRI features of a low-grade chondrosarcoma with peripheral rim enhancement (black arrow) and a nonenhancing low-signal T1 central chondromatous core (white arrow). Note the intermediate signal retained secretions in the obstructed sphenoid sinus (white star).
G. Madani and T.J. Beale
44 metals bound to melanin) and hypointense on T2W images; this tumor most frequently affects the nasal cavity.1 The typical features of T-cell lymphoma are bony destruction in excess of the soft-tissue mass (which may result in misdiagnosis as Wegener’s granulomatoses on CT).10 Soft-tissue sarcomas and B-cell lymphoma usually give rise to a large mass and homogenous contrast enhancement; rhabdomyosarcoma is the most common sinonasal malignancy in children. Aggressive local behavior associated with regional metastases is the hallmark of sinonasal undifferentiated carcinoma and sinonasal neuroendocrine carcinomas. Inverted papillomas have a typically cerebriform configuration on CT and MRI (Fig. 9).11-14
Lymphadenopathy Lymphadenopathy at presentation is observed in around 15% of patients and is associated with a poor prognosis.15 However, metachronous lymph node metastases have a more favorable outcome.16 The posterior nose, ethmoid, and sphenoid sinuses drain to the retropharyngeal lymph nodes as do extensive antral tumors, which invade posterior structures. This lymph node group is not clinically detectable, underlining the importance of imaging.
High Density Within the Sinonasal Cavities on CT Increased density in the paranasal sinuses is a relatively common finding associated with chronic sinonasal inflammatory disease resulting in desiccated secretions—this varies from mildly elevated density to a calcific density. Calcification is also observed in fungal rhinosinusitis and is more likely to be central and fine, whereas nonfungal sinusitis is associated with peripheral and eggshell calcification.17 Linear and nodular calcification occurs in both types.17 An antrolith (rhinolith and sinolith) is a calcified sinonasal
Figure 9 Axial T1-weighted fat-saturated MRI following gadolinium demonstrates the typical cerebriform pattern of inverted papilloma (arrows) in the frontal sinuses.
Figure 10 Coronal CT image showing a large calcified mass, consistent with a rhinolith, surrounded by inflammatory soft tissue in the right nasal cavity.
mass (usually in the nasal cavity or maxillary sinus) often surrounded by inflamed mucosa (Fig. 10). Antroliths are thought to arise due to chronic encrustation of a nidus, which may be endogenous (tooth, sequesterum, old blood products) or exogenous (dental material and foreign bodies passed through the nostrils).
Conclusion The patterns of involvement of the sinonasal cavity and the presence of ancillary features give important clues to the etiology of the disease. Although the majority of sinonasal CT scans simply demonstrate the features chronic inflammatory disease, the radiologist should interrogate the study for clues to more sinister diagnoses.
References 1. Som PM, Brandwein MS: Tumors and tumor-like conditions, in Som PM, Curtin DC (eds): Head and Neck Imaging (ed 4). St Louis, MO, Mosby, 2003, pp 261-373 2. Ashsan F, El-Hakim H, Kim AW: Unilateral opacification of paranasal sinus CT scans. Otolaryngology Head Neck Surg 131(2):53, 2004 3. Maroldi R, Farina D, Battaglia G, et al: MR of malignant nasosinusal neoplasms. Frequently asked questions. Eur J Radiol 24(3):181-190, 1997 4. Som PM, Lawson W, Lidov MW: Simulated aggressive skull base erosion in response to benign sinonasal disease. Radiology 180:755-759, 1991 5. Lund VJ, Lloyd G, Savy L, et al: Fungal rhinosinusitis. J Laryngol Otol 114(1):76-80, 2000 6. Lloyd G, Lund VJ, Beale T, et al: Rhinologic changes in Wegener’s granulomatosis. J Laryngol Otol 116(7):565-569, 2002 7. Som PM, Shapiro MD, Biller HF, et al: Sinonasal tumors and inflammatory tissues: differentiation with MR imaging. Radiology 167:803, 1988 8. Kubal WS: Sinonasal imaging: malignant disease. Semin Ultrasound CT MR 20(6):402-425, 1999 9. Lanzieri CF, Shah M, Krauss D, et al: Use of gadolinium-enhanced MR imaging for differentiating mucoceles from neoplasms in the paranasal sinuses. Radiology 178(2):425-428, 1991 10. Borges A: Skull base tumours part I: imaging technique, anatomy and anterior skull base tumours. Eur J Radiol 66(3):338-347, 2008 11. Lund VJ, Lloyd GA: Radiological changes associated with inverted pap-
Differential diagnosis in sinonasal disease illoma of the nose and paranasal sinuses. Br J Radiol 57(678):455-461, 1984 12. Dammann F, Pereira P, Laniado M, et al: Inverted papilloma of the nasal cavity and the paranasal sinuses: using CT for primary diagnosis and follow-up. AJR Am J Roentgenol 172(2):543-548, 1999 13. Maroldi R, Farina D, Palvarini L, et al: Magnetic resonance imaging findings of inverted papilloma: differential diagnosis with malignant sinonasal tumors. Am J Rhinol 18(5):305-310, 2004 14. Ojiri H, Ujita M, Tada S, Fukuda K: Potentially distinctive features of sinonasal inverted papilloma on MR Imaging. AJR 175:465-468, 2000
45 15. Barnes L, Brandwein M, Som PM: Diseases of the nose, paranasal sinuses, and nasopharynx, in Barnes L (ed): Surgical Pathology of the Head and Neck (ed 2). New York, NY, Marcel Decker, 2001, pp 439555 16. Gullane PJ, Conley J: Carcinoma of the maxillary sinus: a correlation of the clinical course with orbital involvement, pterygoid erosion or pterygopalatine invasion and cervical metastases. J Otolaryngol 12: 141-145, 1984 17. Yoon JH, Na DG, Byun HS, Koh YH, Chung SK, Dong HJ: Calcification in chronic maxillary sinusitis: comparison of CT findings with histopathologic results. AJNR Am J Neuroradiol. 20(4):571-4, 1999
I
nflammatory sinonasal disease is ubiquitous, whereas benign and malignant sinonasal tumors are uncommon. The clinical presentation of sinonasal pathology is nonspecific, including facial pain, purulent nasal discharge, epistaxis, and nasal obstruction. A key role of imaging is to distinguish inflammatory, benign, and malignant disease. This article highlights features that aid differential diagnosis.
Diagnostic Clues and Pitfalls Computed tomographic (CT) imaging of the sinonasal cavity is commonly performed; the main indications are in recurrent disease, disease unresponsive to medical treatment, and unilateral symptoms and to provide a roadmap for functional endoscopic surgery. By far, the most common finding is polypoid mucosal thickening due to inflammatory disease or sinonasal polyposis. The radiological features that should alert the radiologist to the possibility of malignancy are as follows: ● ● ● ● ●
Unilateral sinus disease Bony involvement Extensive soft-tissue mass Tumor necrosis Lymphadenopathy
Unilateral Sinus Disease Unilateral sinus disease raises the suspicion of benign or malignant neoplasia (Fig. 1). Early malignancy commonly mimics polypoid mucosal thickening on CT and the unilaterality of the changes may be the only imaging clue.1 A retrospective review of 1118 CT scans of the paranasal sinuses identified
*Imperial College NHS Trust, St. Mary’s Hospital, London, UK. †University College Hospital London, London, UK. Address reprint requests to: Timothy J. Beale, FRCR, FRCS, University College Hospital London, 235 Euston Road, London NW1 2BU, UK. E-mail: [email protected]
0887-2171/09/$-see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1053/j.sult.2008.10.014
28 cases of unilateral sinus disease of which 12 cases were due to neoplasia (6 malignant).2
Bony Involvement There are four patterns of bony involvement in sinonasal disease. Bony erosion is highly suspicious of malignancy and is the typical pattern of involvement in squamous cell carcinoma (Fig. 2A) but may also be observed in inflammatory conditions.3 In particular, inflammation involving the bones of the skull base frequently mimics malignancy.4,5 Bony remodeling, which is more typical of inflammatory conditions such as mucoceles, is also seen in less aggressive malignancies such as olfactory neuroblastoma (Fig. 2B) and benign tumors. Reactive sclerosis is the hallmark of chronic inflammation (Fig. 2C). New bone formation is a feature of chondrosarcoma and osteosarcoma. Wegener’s granulomatosis, fungal infections such as mucormycosis, and reparative granuloma (Fig. 3) frequently have aggressive imaging appearances and mimic malignancy. The coexistence of bony erosion and sclerosis is characteristic of Wegener’s granulomatosis but may also be observed in fungal infections (Fig. 4), adenoid cystic carcinoma, as well as cases where chronic infection is superimposed on malignancy.6 Other benign lesions that may mimic malignancy by causing bony erosion include Brown’s tumor of hyperparathyroidism (Fig. 5), inverted papillomas, and ameloblastoma. New bone formation may be in the form of stippled “chondroid” calcification, which occurs in well-differentiated chondrosarcoma; these calcified foci have low T1-weighted (T1W) and high T2W signal on magnetic resonance imaging (MRI). A sunburst periosteal reaction is highly suspicious of osteosarcoma but a soft-tissue mass causing bony destruction and containing areas of sclerosis (due to matrix mineralization) is a more common finding. Fibrous dysplasia and Paget’s disease have variable MRI appearances depending on the degree of sclerosis, cystic components, and marrow replacement. Both conditions 39
40
G. Madani and T.J. Beale
Figure 1 Unilateral sinus disease. (A) Coronal CT and (B) T2W coronal MRI demonstrating unilateral sinus disease. This is suspicious for neoplastic disease. In this case, an inverted papilloma obstructing the maxillary ostium (arrow) resulted in intermediate signal desiccated antral secretions.
Figure 2 Different types of bone involvement. (A) Coronal CT shows bone erosion and destruction of the bone margins (arrows) by an aggressive malignancy. (B) Coronal CT demonstrates benign bone expansion and remodeling (arrow) in a case of olfactory neuroblastoma. (C) Axial CT image shows reactive bone sclerosis typical of chronic inflammatory disease (arrow).
Differential diagnosis in sinonasal disease
41
Figure 3 Reparative granuloma. (A) Axial and (B) coronal CT images show an expansile and destructive mass centered on left posterior ethmoid and sphenoid sinuses, which was histologically proven to be a reparative granuloma.
cause bone expansion, may enhance avidly, and are easily confused with tumor on MRI but are confidently diagnosed on CT.
Soft-Tissue Abnormalities The majority of sinonasal tumors are of low to intermediate signal intensity on all MRI sequences (Fig. 6); areas of signal heterogeneity may arise due to hemorrhage and necrosis (Fig. 7). Hemorrhage may result in foci of high T1W signal but the T2W signal intensity of blood products is usually low. Thus T2W sequences are usually superior in distinguishing tumor
from inflammatory disease.7 Minor salivary gland tumors present a potential diagnostic pitfall as they may be T2 hyperintense depending on their mucin content and cellularity.7 On MRI, chondrosarcoma, particularly small foci of recurrent disease, may mimic inflammatory disease as they are typically T1 hypointense and T2 hyperintense (Fig. 8). The potential coexistence of inflammatory and malignant disease presents a further diagnostic challenge. Chronic inflammation results in a variety of signal intensities on all sequences due to the absorption of free water by hydrophilic mucoproteins and may therefore mimic malignancy. However, contrast enhancement usually allows the differentiation
Figure 4 Fungal sinusitis (A) axial and (B) coronal CT scans. There is extensive bone remodeling with sinus expansion and bone thinning. The high density within the sinuses is suggestive of fungal infection.
42
Figure 5 Brown tumor. (A) Coronal CT scan. The expansile and destructive mass eroding through the lateral and medial walls of the left maxillary antrum is a brown tumor of hyperparathyroidism and may easily be mistaken for malignancy. (B) Plain film radiograph shows the classic subperiosteal bone resorption on the radial aspect of the middle phalanges.
Figure 6 Typical MRI features of sinonasal tumors. (A) Axial T1W MRI and (B) axial fat saturation T1W gadolinium-enhanced MRI demonstrate an intermediate signal intensity and moderately enhancing mass, extending from the ethmoid sinus into the right anterior sphenoid (white arrows) and left cavernous sinus (black arrows). (C) Axial T2W MRI differentiates the intermediate signal intensity tumor (white stars) from the high signal inflammatory secretions (black stars) in the remaining sphenoid and ethmoidal cells. This tumor is an adenocarcinoma, although its radiological features are nonspecific.
G. Madani and T.J. Beale
Differential diagnosis in sinonasal disease
43
Figure 7 Tumor necrosis. (A) Axial CT and (B) axial T1W MRI demonstrating an advanced squamous cell carcinoma of the maxillary antrum. Note the erosion of the anterior, posterior, and medial walls of the antrum (arrows), demonstrated on both modalities. The tumor contains a central area of necrosis (star).
of moderately enhancing tumor from the bright peripheral enhancement of inflammation and nonenhancement of retained secretions (Fig. 6).8,9 Furthermore, inflammatory sinonasal disease enhances more avidly than malignancy.7 Malignant tumors may exhibit homogeneous or heterogeneous enhancement with complete failure of enhancement of areas of necrosis (Fig. 7). Occasionally, tumors of salivary origin such as adenoid cystic carcinoma show high signal intensity on T2W images, potentially mimicking inflammatory disease, but are usually
distinguishable from inflammatory disease by their enhancement characteristics. Malignant tumors may exhibit homogeneous or heterogeneous enhancement with failure of enhancement of areas of necrosis. There are a few features that raise the possibility of a specific histological subtype. Peripheral areas of cystic degeneration and calcific foci are features associated with olfactory neuroblastoma (esthesioblastoma) but only occur in the minority of cases. Malignant melanoma may be hyperintense on T1W (due to hemorrhage and the paramagnetic effect of
Figure 8 Chondrosarcoma on MRI (A) and (B) axial and sagittal T1W gadolinium-enhanced images, demonstrating the typical MRI features of a low-grade chondrosarcoma with peripheral rim enhancement (black arrow) and a nonenhancing low-signal T1 central chondromatous core (white arrow). Note the intermediate signal retained secretions in the obstructed sphenoid sinus (white star).
G. Madani and T.J. Beale
44 metals bound to melanin) and hypointense on T2W images; this tumor most frequently affects the nasal cavity.1 The typical features of T-cell lymphoma are bony destruction in excess of the soft-tissue mass (which may result in misdiagnosis as Wegener’s granulomatoses on CT).10 Soft-tissue sarcomas and B-cell lymphoma usually give rise to a large mass and homogenous contrast enhancement; rhabdomyosarcoma is the most common sinonasal malignancy in children. Aggressive local behavior associated with regional metastases is the hallmark of sinonasal undifferentiated carcinoma and sinonasal neuroendocrine carcinomas. Inverted papillomas have a typically cerebriform configuration on CT and MRI (Fig. 9).11-14
Lymphadenopathy Lymphadenopathy at presentation is observed in around 15% of patients and is associated with a poor prognosis.15 However, metachronous lymph node metastases have a more favorable outcome.16 The posterior nose, ethmoid, and sphenoid sinuses drain to the retropharyngeal lymph nodes as do extensive antral tumors, which invade posterior structures. This lymph node group is not clinically detectable, underlining the importance of imaging.
High Density Within the Sinonasal Cavities on CT Increased density in the paranasal sinuses is a relatively common finding associated with chronic sinonasal inflammatory disease resulting in desiccated secretions—this varies from mildly elevated density to a calcific density. Calcification is also observed in fungal rhinosinusitis and is more likely to be central and fine, whereas nonfungal sinusitis is associated with peripheral and eggshell calcification.17 Linear and nodular calcification occurs in both types.17 An antrolith (rhinolith and sinolith) is a calcified sinonasal
Figure 9 Axial T1-weighted fat-saturated MRI following gadolinium demonstrates the typical cerebriform pattern of inverted papilloma (arrows) in the frontal sinuses.
Figure 10 Coronal CT image showing a large calcified mass, consistent with a rhinolith, surrounded by inflammatory soft tissue in the right nasal cavity.
mass (usually in the nasal cavity or maxillary sinus) often surrounded by inflamed mucosa (Fig. 10). Antroliths are thought to arise due to chronic encrustation of a nidus, which may be endogenous (tooth, sequesterum, old blood products) or exogenous (dental material and foreign bodies passed through the nostrils).
Conclusion The patterns of involvement of the sinonasal cavity and the presence of ancillary features give important clues to the etiology of the disease. Although the majority of sinonasal CT scans simply demonstrate the features chronic inflammatory disease, the radiologist should interrogate the study for clues to more sinister diagnoses.
References 1. Som PM, Brandwein MS: Tumors and tumor-like conditions, in Som PM, Curtin DC (eds): Head and Neck Imaging (ed 4). St Louis, MO, Mosby, 2003, pp 261-373 2. Ashsan F, El-Hakim H, Kim AW: Unilateral opacification of paranasal sinus CT scans. Otolaryngology Head Neck Surg 131(2):53, 2004 3. Maroldi R, Farina D, Battaglia G, et al: MR of malignant nasosinusal neoplasms. Frequently asked questions. Eur J Radiol 24(3):181-190, 1997 4. Som PM, Lawson W, Lidov MW: Simulated aggressive skull base erosion in response to benign sinonasal disease. Radiology 180:755-759, 1991 5. Lund VJ, Lloyd G, Savy L, et al: Fungal rhinosinusitis. J Laryngol Otol 114(1):76-80, 2000 6. Lloyd G, Lund VJ, Beale T, et al: Rhinologic changes in Wegener’s granulomatosis. J Laryngol Otol 116(7):565-569, 2002 7. Som PM, Shapiro MD, Biller HF, et al: Sinonasal tumors and inflammatory tissues: differentiation with MR imaging. Radiology 167:803, 1988 8. Kubal WS: Sinonasal imaging: malignant disease. Semin Ultrasound CT MR 20(6):402-425, 1999 9. Lanzieri CF, Shah M, Krauss D, et al: Use of gadolinium-enhanced MR imaging for differentiating mucoceles from neoplasms in the paranasal sinuses. Radiology 178(2):425-428, 1991 10. Borges A: Skull base tumours part I: imaging technique, anatomy and anterior skull base tumours. Eur J Radiol 66(3):338-347, 2008 11. Lund VJ, Lloyd GA: Radiological changes associated with inverted pap-
Differential diagnosis in sinonasal disease illoma of the nose and paranasal sinuses. Br J Radiol 57(678):455-461, 1984 12. Dammann F, Pereira P, Laniado M, et al: Inverted papilloma of the nasal cavity and the paranasal sinuses: using CT for primary diagnosis and follow-up. AJR Am J Roentgenol 172(2):543-548, 1999 13. Maroldi R, Farina D, Palvarini L, et al: Magnetic resonance imaging findings of inverted papilloma: differential diagnosis with malignant sinonasal tumors. Am J Rhinol 18(5):305-310, 2004 14. Ojiri H, Ujita M, Tada S, Fukuda K: Potentially distinctive features of sinonasal inverted papilloma on MR Imaging. AJR 175:465-468, 2000
45 15. Barnes L, Brandwein M, Som PM: Diseases of the nose, paranasal sinuses, and nasopharynx, in Barnes L (ed): Surgical Pathology of the Head and Neck (ed 2). New York, NY, Marcel Decker, 2001, pp 439555 16. Gullane PJ, Conley J: Carcinoma of the maxillary sinus: a correlation of the clinical course with orbital involvement, pterygoid erosion or pterygopalatine invasion and cervical metastases. J Otolaryngol 12: 141-145, 1984 17. Yoon JH, Na DG, Byun HS, Koh YH, Chung SK, Dong HJ: Calcification in chronic maxillary sinusitis: comparison of CT findings with histopathologic results. AJNR Am J Neuroradiol. 20(4):571-4, 1999