Presentation
Tobacco smoker with 1 year history of reduced exercise tolerance and 10 kg of unintentional weight loss.
Patient Data
On the PA projection, there is complete whiteout of the right lung characterised by a veiling opacity of the right hemithorax with pulmonary vessels visible through the opacity. There are no air bronchograms. There is a small dense right pleural effusion with adjacent compressive atelectasis. The right heart border is completely obscured and there is slight mediastinal shift to the left. There is also mild elevation of the right hemidiaphragm.
On the lateral projection, the opacity is revealed to be an anterior mass. There is loss of the retrosternal clear space and the posterior lung fields are generally clear. On careful inspection of the PA projection, the well-defined medial edge of the mass is clearly visible. It forms an acute angle with the mediastinal pleura, placing the mass within the lung parenchyma.
CT shows a large lobulated mass within the right hemithorax anteriorly measuring 12 x 14 x 15 cm (AP x TR x CC). It is homogeneously hypodense with no visible cavitation, calcification, septations, or enhancement.
The mass is centred at the right hilum, encasing the right main bronchus and compressing the right upper and middle lobe bronchi leading to complete lobar atelectasis. There is also partial effacement of the SVC and mild leftward mediastinal shift. The mass is contiguous with a filling defect that extends from the right superior pulmonary vein into the left atrium in keeping with local vascular invasion.
There is no pleural thickening. No invasion into the adjacent chest wall or ribs. No metastases to the lymph nodes, bony thorax, or upper abdominal viscera.
There is a small right pleural effusion and mild dependent atelectasis of the lower lobes. The left lung is generally clear apart from some scattered non-specific ground-glass opacities at the apex. There are no pulmonary nodules. There is a small pericardial effusion.
The mass is most in keeping with a primary lung carcinoma (small cell lung cancer is favoured due to its large size and perihilar location). A mediastinal malignancy (such as lymphoma or a germ cell tumour) is a less likely differential.
The pulmonary mass demonstrates intense peripheral FDG avidity (SUV 12.3). There are large regions of photopaenia centrally consistent with necrosis.
The abnormal FDG activity abuts the right aspect of the trachea and oesophagus with extension into the right hilar and mediastinal nodal stations.
There is a second intensely FDG avid (SUV 9.0) lesion within the right frontal lobe of the brain in keeping with metastasis.
Case Discussion
A CT-guided biopsy was performed.
Histology
Sections show thin core biopsies including broad areas of necrosis. There is tumour with myxoid background with areas of spindle cells, some of which are plump and with nuclear hyperchromasia, and scattered larger atypical pleomorphic cells with prominent eosinophilic nucleoli. Cytoplasm is indistinct and pale to eosinophilic in the larger cells. Mitotic activity is identified.
Immunohistochemistry
There is focal minimal staining for Cam 5.2 (favour non-specific). P63 shows focal positive staining and ERG is positive. SMA is positive. Focal TTF-1 staining is seen. CD31 is equivocal/weak focal. Negative stains include AE1/AE3, CK5/6, desmin, S100, SOX-10, WT-1, calretinin, and STAT-6 (focal minimal non-specific cytoplasmic staining only). BAP-1 is positive (retained). CD99 shows positive staining. Approximately <1% of tumour cells show membranous staining for PDL-1.
Pathologist comment
The appearances are those of a spindling and pleomorphic sarcomatoid tumour with areas of necrosis. No definite morphologic features of differentiation are identified and the immunohistochemical stains are somewhat non-specific. The histogenesis of the tumour is uncertain although it could represent a sarcomatoid component of a sarcomatoid carcinoma or sarcomatoid mesothelioma. Other possibilities could include primary spindling/pleomorphic sarcoma (including high grade component of malignant peripheral nerve sheath tumour).
Final radiological and histopathological diagnosis
Metastatic spindling and pleomorphic sarcomatoid carcinoma.
Pulmonary sarcomatoid carcinoma is a rare (0.1-0.4% of malignant lung tumours), poorly-differentiated, and highly aggressive tumour with a poor prognosis 1. The patient subsequently underwent palliative radiotherapy and chemoimmunotherapy, and passed away within a year.
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