Identification of CT Features to Differentiate Pulmonary Sarcoma from Carcinoma

Abstract

Background Primary lung sarcoma (PLS) differs in management protocols and prognosis from the more common primary lung carcinoma (PLC). It becomes imperative to raise a high index of suspicion on radiological and pathological features. Purpose The aim of this study is to highlight the variable imaging appearances of PLS compared with PLC, which impacts radiologic - pathologic correlation. Materials and Methods A retrospective observational study of 68 patients with biopsy-proven lung tumors who underwent baseline imaging at our tertiary care cancer hospital was conducted between January 2018 and March 2022. The patient details and imaging parameters of the mass on contrast-enhanced computed tomography (CECT) were recorded and analyzed for patients with PLS and compared with PLC. Follow-up imaging was available in 9/12 PLS and 52/56 PLC patients. Results Among 12 patients with PLS, 5 patients had synovial sarcoma on histopathology. PLS was seen in patients with a mean age of 40.8 years; the mass showed a mean size of 13.2 cm, lower lobe (75%), parahilar (75%), hilar involvement (41.7%), oval shape (41.7%), circumscribed (25%) or lobulated (75%) margins, lower mean postcontrast attenuation of 57.3 HU, fissural extension (50%), calcification (50%), and no organ metastasis other than to the lung. PLC (56 patients) was seen in the elderly with a mean age of 54.8 years; the mass showed a mean size of 5.7 cm, irregular shape (83.9%), spiculated margins (73.2%), higher mean postcontrast attenuation (77.3 HU), chest wall infiltration (30.4%), and distant metastasis (58.9%) at baseline imaging. A statistically significant difference ( p < 0.05) was seen between sarcoma and carcinoma in the mean age, size, site, shape, margins, postcontrast attenuation, presence of calcifications, fissural extension, and distant metastasis. Conclusion The distinct imaging features of sarcoma help in differentiating it from carcinoma. This can also be used to corroborate with histopathology to achieve concordance and guide clinicians on further approach.

Keywords: SYT–SSX fusion protein; carcinoma; lung neoplasms; sarcoma; synovial sarcoma.

Fig. 1

Flowchart demonstrating the study protocol. CECT, contrast-enhanced computed tomography.

Fig. 2

Computed tomography (CT) features of synovial sarcoma. ( A,B ) Axial and coronal contrast-enhanced computed tomography (CECT) images of a 36-year-old man presenting with chest pain and dyspnoea show a heterogeneous parahilar mass ( asterisk ) extending into the right lower lobe with fissural extension, mediastinal invasion ( white arrows ), and bronchial narrowing ( thick arrow ) and minimal right pleural effusion ( black arrow ). ( C ) Axial and ( D ) coronal CECT images of a 28-year-old woman presenting with cough and dyspnoea show a large circumscribed pleuropulmonary mass in the left hemithorax ( asterisk ) with necrosis and collapse of the lung parenchyma. Both lesions were proven to be synovial sarcoma by biopsy.

Fig. 3

Endobronchial extension of synovial sarcoma. ( A ) Axial and ( B,C ) coronal reformatted contrast-enhanced computed tomography (CECT) images of a 38-year-old man, a farmer, presenting with cough, expectoration, and dyspnoea show a mass in the left lower lobe ( asterisk ) with extension into the lobar bronchus ( arrow ) and resultant lung collapse. ( D ) Hematoxylin and eosin (×100) staining of biopsy core showed multiple spindle cells showing round hyperchromatic nuclei and occasional glandular components. Further evaluation for SSX translocation was positive on in situ hybridization.

Fig. 4

Computed tomography (CT) features of synovial sarcoma. ( A ) Axial and ( B ) coronal reformatted contrast-enhanced computed tomography (CECT) images of a 25-year-old man with chest pain and hemoptysis show a right upper lobe mass with an intratumoral pseudoaneurysm ( thick arrow ), partial superior vena cava (SVC) compression ( black arrow ), circumscribed margins despite the large size ( white arrow ), and loculated pleural effusion ( asterisk in B ), proven to be synovial sarcoma by biopsy.

Fig. 5

Desmoplastic small round cell tumor (DSRCT) of pleural origin in a 46-year-old woman with dyspnoea and facial puffiness. ( A ) Axial and ( B ) coronal reformatted contrast-enhanced computed tomography (CECT) shows a heterogeneously enhancing mass with necrosis and calcifications compressing the superior vena cava (SVC) and right atrium ( black arrows ).

Fig. 6

Undifferentiated sarcoma in a 60-year-old man presenting with dyspnea, cough with expectoration. ( A ) Axial and ( B ) sagittal reformatted contrast-enhanced computed tomography (CECT) images show lobulated margins ( white arrows ) of the mass in the left lower lobe and bronchial encasement ( asterisk ).

Fig. 7

Sarcomatoid carcinoma in a 68-year-old man, smoker, presenting with dyspnea, cough, and chest pain. ( A ) Axial and ( B ) sagittal reformatted contrast-enhanced computed tomography (CECT) images show a large necrotic mass involving the entire left upper lobe with the presence of calcifications ( arrow in A ), cavitation ( arrow in B ), and mild left pleural effusion ( black arrow in B ).

Fig. 8

Difference in postcontrast attenuation of lung masses. ( A ) Axial contrast-enhanced computed tomography (CECT) image shows an irregular lobulated mass with areas of necrosis, chest wall infiltration ( white arrow in A ) and rib destruction ( black arrow in A ). The postcontrast attenuation of the mass (62 HU) is less than the adjacent muscle (66 HU). This was proven to be SMARCA4 -deficient undifferentiated tumor on biopsy. ( B ) In comparison, attenuation of the squamous cell carcinoma was 82 HU in a different patient where muscle showed an attenuation of 57 HU.

Fig. 9

Ewing's sarcoma in an 18-year-old woman presenting with chest pain. ( A ) Axial and ( B ) sagittal reformatted contrast-enhanced computed tomography (CECT) images show a heterogeneous mass with necrosis, chunky calcifications, and adjacent rib sclerosis and erosion ( thick arrow ).

Fig. 10

Liposarcoma in a 54-year-old woman presenting with back pain and incidentally detected mass on radiograph. ( A ) Axial and ( B ) coronal reformatted contrast-enhanced computed tomography (CECT) images show a circumscribed mass of extrapleural origin ( asterisk ) with a mean of 21 HU, proven to be round cell liposarcoma by biopsy.

Fig. 11

Inflammatory myofibroblastic tumor (IMFT) in a 23-year-old woman presenting with cough, hemoptysis, dyspnea, and dysphagia. Mediastinal and lung windows of axial ( A,C ) and coronal reformatted ( B,D ) contrast-enhanced computed tomography (CECT) images show a large mass with chunky calcification ( asterisk ) occupying almost the entire right lung, with cutoff of the right main bronchus ( black arrow in D ), mediastinal extension, and rib crowding in the right upper lobe with loculated pleural effusion ( white arrow in C ). Note the deviated dilated esophagus with air fluid level ( thick arrow in C ).

Fig. 12

Contrast-enhanced computed tomography (CECT) features of lung carcinomas. ( A ) Axial CECT image of a 71-year-old male, smoker, presenting with dyspnoea and chest pain shows a heterogeneously enhancing mass with internal cavitation and extensive infiltration into chest wall, rib, and vertebral destruction ( thick arrows ). The final histology was squamous cell carcinoma. ( B ) Lung window of axial CECT image of a 53-year-old man presenting with cough and expectoration shows a mass with spiculated margins ( black arrows ), multiple satellite nodules, nodules in adjacent lobe, and metastases in the opposite lung ( white arrows ). The final histology was poorly differentiated adenocarcinoma.

Fig. 13

Contrast-enhanced computed tomography (CECT) features of lung carcinomas. ( A ) Lung window of axial CECT image of a 56-year-old male, smoker, presenting with cough and expectoration shows an irregular mass with surrounding ground glass opacities and lymphatic spread in the form of perilymphatic nodules and septal thickening ( curved arrow ) in the left lung. ( B ) Corresponding hematoxylin and eosin (H&E; ×100) staining of biopsy specimen shows multiple glandular areas of neoplastic cells, proven to be acinic predominant adenocarcinoma.

Fig. 14

Bronchovascular infiltration in lung carcinomas. Coronal ( A ) mediastinal and ( B ) lung windows of contrast-enhanced computed tomography (CECT) images in a 43-year-old male smoker shows a spiculated mass encasing the branches of the right pulmonary artery, right inferior pulmonary vein ( white arrows in A ) with complete cutoff of the right lower lobe bronchus and narrowing of the right main bronchus ( thick arrow in B ), proven to be adenocarcinoma. ( C ) Coronal CECT image of a 61-year-old man, smoker, presenting with chest pain and edema of the upper extremity shows superior vena cava (SVC) obstruction ( curved arrow ) in a poorly differentiated adenocarcinoma. ( D ) Axial CECT image of a 51-year-old man, smoker, complaining of cough and chest pain shows SVC narrowing ( black arrow ) by small cell carcinoma ( thick arrow ) with resultant formation of chest wall collaterals ( white arrow ).