Diagnostic Performance of CT Scan in Sinonasal Mass

Background: CT imaging of nose and paranasal sinuses is to confirm the diagnosis, localize the disease, characterize the extent of pathology and describe any anatomical variations. A careful histopathological examination (HPE) is nesessary to decide the nature of a specific lesion. Objective: To observe performance of CT scan as a sensitive modality in the diagnosis of sinonasal mass by comparing with the findings of histopathological examination. Methods: This cross sectional study in Dhaka Medical College Hospital (DMCH). From 01/ 07/2013 to 30/06/2014 (One year), 42 patients were selected. Resuls: Here male and female ratio was found 1.4:1 So, the incidence of sinonasal growth slightly higher in male (59.3%) compared to the female (40.6%).Incidence of malignant tumour was found more in age group above 60 years. Out of 32 patients, 6 patients (18.7%) were diagnosed histopathologically as infective, 7 patients (21.8%) were benign and 19 patients (59%) had malignant sinonasal mass.


Introduction:
Plain sinus films do not allow adequate evaluation of the sinonasal masses because of overlapping of structures and other limitations. So they are inaccurate in high percentage of patients and have been supplemented by CT imaging 1 The purpose of CT imaging of nose and paranasal sinuses is to confirm the diagnosis, localize the disease, characterize the extent of pathology and describe any anatomical variations.
As a general rule, malignant tumours destroy bone, where as benign processes cause thickening or remodeling of adjacent bone 2 . Bone changes are depicted better with computed tomography. All malignant tumours do not destroy bone, however. The true value of CT scanning is its ability to detect bone erosion 3 .
Extensions of the tumour into the intracranial cavity, orbit, pterygomaxillary fossa or into the soft tissues of the face is easily demonstrated on CT. The accuracy of CT in determining tumour spread to these areas is on the order of 85% 4 .
In spite of these properties, it is not always possible to distinguish tumour from mucosal oedema secondary to sinus obstruction by the lesion on CT. In addition, CT can not always clearly determine whether the tumour has invaded the periorbita (important for planning need for orbital exenteration) 5,6 .

Methods:
It was a cross sectional observational study. This prospective study was carried out in the department of Radiology and Imaging in collaboration with department of ENT Department of DMCH, Dhaka, during the period of July 2013 to June 2014 (One year). Total number of 42 patients were included in this study. This was a non random purposive sampling.

CT Examination Technique
All CT examination were performed with 64 slice spiral CTscan machine (HITACHI), both non-contrast and contrast axial scan and coronal reconstruction were performed with following parameters.

Imaging variables
CT Scan findings-CT scan diagnosis of different maxillary growth, Density of the lesion, Site of origin, Unilateral or bilateral sinus involvement, Character of enhancement of lesion, Bone destruction, Spread to other organs

Histopathological comparison
The postoperative resected tissues were examined histopathologically in the respective pathology department and then collected reports were compared with CT scan findings.

Data Collection Procedure
The aims of study were explained to the patients and informed written consent was taken. Data were collected by face to face interview, from history sheet, CT scan and pathological findings of the patients. All the data were recorded in a pre-designed structured data collection sheet.

Data Analysis
All the data were checked and compiled after collection. The data were entered into the computer and analyzed with the help of Statistical Package for Social Sciences (SPSS) software programmed. An analysis plan has developed keeping in view with the objectives of the study. For the validity of the study outcome sensitivity, specificity, accuracy, positive and negative predictive value were calculated out after confirmation of histopathological diagnosis. For significance of differences chi-square test were done where applicable. Statistical significance was set at P< 0.05 and confidence interval was set at 95% level.

Results:
This study included 32 patients who were suspected case of sinonasal mass subsequently confined by CT scan and histopathology.
Age and Sex distribution. The age range from 10 years to 75 years and the mean age (±SD) was 35.2±21.3 years in male and 37.0±23.1 years in female. Overall mean age (±SD) was 35.94±21.3 years. Highest incidence of found between 10-19 years of age group.

Age group and histopathological relation
Out of 32 patients 13 were below the age group 20 years (40.6%), 7 cases were within 20-40 years age group (21.83%), 4 cases were within 41-60 years age group (12.53%) and 8 patients were above the age group 60 years (25%)Below 20 years out of 13 patients CT diagnosis were 3 were infective, 3 were benign and 6 were malignant mass. Whereas histolpathology showed 6 cases were infective, 4 cases were benign and 4 cases were malignant tumour. Within 20-40 years age group out of 7 patients CT scan showed 1 case was infective, 4 cases were benign and 2 cases were malignant mass. Among 4 cases age within 40-60 years CT diagnosis showed 1 case was infective, 1 case was benign and 2 cases were malignant masses.
Out of 8 patients above 60 years of age, all the 8 cases were diagnosed as malignant masses by both CT and histopathology. Infective and benign lesion in this age group was found zero.

Sex group and histopathological relation:
Out of 32 patients 19 were male (59.3%) and 13 were female (40.6%) here male and female ratio was found 1.4:1. The male patients presented with sinonasal masses were little more than that of female.
Out of 19 male patients histopathology showed 5 patients positive for infective, 4 patients positive for benign and 10 patients were found malignant lesion.
Out of 13 female patients histopathologically positive-1 cases were infective, 3 cases were benign and 9 cases were malignant sinonasal growth.
Again out of 19 male patients CT examination revealed that 5 patients were infective, 5 patients were positive for benign and 9 patients were malignant lesion.
Out of 13 female patients CT examination found 2 were infective, 3 cases were benign and 8 cases were malignant sinonasal mass.

Distribution of clinical presentation and histopathological diagnosis:
The most common symptoms associated with sinonasal growth was nasal blockage which was observed in 24 (80%) patients, out of 24 cases 9 were infective, 9 were benign and 6 were malignant lesion. 12 patients (40%) had epistaxis, among them 6 cases were infective, 4 cases were benign and 2 were malignant lesions. Propotosis noted in 9 patients (30%) out of which 2 patients histopathologically proved infective, 3 were benign and 4 were malignant maxillary sinus lesion. Eyeache was in 12 patients (40%) out of which 6 were found infective, 3 were benign and 3 patients were malignant sinonasal mass. Gradual swelling of face in 6 patients (20%), out of which histopathology shows 1 was inflammatory, 1 was benign and 4 were malignant cases. The results of CT scan and histopathological correlation in the following table shows there was significant correlation.

Comparison
of CT diagnosis and Histopathological diagnosis: Out of 32 patients of sinonasal mass 5 patients were diagnosed as infective mass by CT scan whereas histopathology showed 6 cases were infective. 9 patients were diagnosed as benign mass by CT scan whereas histopathological report evident that 7 cases were benign and 1 case was infective lesion and 1 malignant lesion. Total 18patients were diagnosed as malignant tumour by CT scan whereas histopathology showed 19 cases were malignant. Correlation between CT diagnosis and histopathological diagnosis are represented by the following table.

A. For Infective mass:
Out of 32 patients 5 cases were diagnosed as infective mass by CT scan and confirmed by histopathological examination; they are true positive. 9 cases were dignosed as benign but among them 1 case was infective; it was false negative.All 5 patients diagnosed by CTscan as infective mass were also diagnosed hispathologically as infective mass,so there was no false positive. 26 patients were found negative by both of CT and histopathology; these 26 were true negative.

B) For benign mass
Out of 32 patients 9 patients were diagnosed as benign mass both by CT. But 7 case was diagnosed as benign by histopathologically; they are true positive. 2 case was diagnosed by CT as benign mass but histopathologically it was negative; it was false negative. Among CT positive for benign lesion no case was diagnosed by histopathology as negative so there was no false nagative . 23 cases were found negative by both of CT and histopathology; these were true negative and shown in the Table-VIII.

C) For malignant mass
Out of 32 patients 18 cases were positive by both of CT and histopathology; these 18 cases were true positive. no patient was positive by CT but was negative in histopathology; it was false positive. 1cases were negative by CT but were positive histopathologically; they were false negative. Remaining 13 patients were negative by both of CT and histopathology; they were true negative. The results of CT were correlated with histopathology are given in the following Table-IX. Plain radiograph has limited role in detecting extension and bony involvement of sinonasal lesion. Besides being expensive, MRI cannot provide detailed information regarding bony destruction or remodeling. The study was carried out to determined the usefulness of CT scan in the diagnosis of sinonasal mass compared with histopathological study. Most tumours originated in the maxillary and in the ethmoidal sinus. Sphenoid sinus is divided into right and left parts by a bony septum. Few tumors arises from here.

Discussion:
This study was carried out with a aim to establish the usefulness of the CT scan in preoperative evaluation of sinonasal mass and their histopathological correlation of postoperative resected tissues along with its validity test by calculating sensitivity, specificity, accuracy, positive predictive value respectively 7,8 .
In this study concern about the age the highest incidence of disease was found below 20 years of age group (40%) and infective lesion of the maxillary antrum is more common in below 20 years of age. This study also showed malignant tumour most common in the people over 60 years of age. Regarding Positive predictive value = 78%, Negative predictive value = 100%, Accuracy rate = 93.33% Positive predictive value = 94%, Negative predictive value = 100%, Accuracy rate = 96% maxillary antral mass the age range 10-80 years in male and female age range 34 -75 years 9,10 . The age range of this study which is almost similar to the study of Hone et al.
This study was carried out on 32 patients by plain X-ray and clinically suspected sinonasal growth, came in the inpatient and outpatient department of Dhaka Medical College. Initially 42 patients were selected with clinical findings of sinonasal growth; out of them 10 were excluded from the study because 4 of them refused to do operation and 6 for non availability of histopathological report. In this study 30 patients were divided into 4 group on the basis of age. The age of the subjects in this study was range from 10-74 years. The mean age (±SD) was 35.2±21.3 years in male and 37.0±23.1 years in female. Overall mean age (±SD) was 35.94±21.3 years.
The highest incidence of disease was found in between 10-19 years of age group (40%) and lowest in between 41-60 years (13.33%). The invective lesion of the nose and paranasal sinuses are more common in the age group below 20 years. Malignant lesions were found more common over 60 years of age. The correlation between CT scan and histopathology in patients with sinonasal mass was observed in this study, p value is based on chi-square test which reveals significant correlation between the two modalities.

Summary:
Computed tomography (CT) scan is very effective and sensitive diagnostic imaging modality in the diagnosis and evaluation of sinonasal mass.

Conclusion:
Computed tomography (CT) scan examination of the sinonasal mass correlate well in most of the cases with histopathological results. It is therefore can be concluded that CT examination of nose and paranasal sinus is a useful modality in the evaluation of sinonasal mass.