The Pleura: Talc Pleurodesis vs. Inflammation vs. Malignancy
Talc Pleurodesis:
Talc pleurodesis is performed to obliterate the pleural space, typically in cases of recurrent pleural effusions or pneumothorax. Talc causes an inflammatory reaction, which fuses the parietal and visceral pleura.
The procedure results in intensely avid pleural thickening, which can be confused with pleural malignancy (typically metastatic disease, mesothelioma or lymphoma). The intensely avid appearance of talc pleurodesis may persist for decades after the procedure.
As oncology patients very commonly require pleurodesis, radiologists must be very comfortable with its PET/CT characteristics.
Fortunately, its characteristic hyperdense appearance on CT readily distinguishes it from pleural malignancy (knowing the history also helps…)
Imaging Characteristics:
- Intensely avid pleural thickening, usually with nodular components.
- Non-uniform distribution; much of the pleura may be spared.
- Hyperdense appearance on CT makes the diagnosis.
Be mindful that patients who have undergone talc pleurodesis may also have co-existing active plural malignancy in other areas of their pleura. Distinguishing and localizing these separate entities will help the clinician direct appropriate therapy.
Inflammatory FDG-Avid Pleural Thickening After Pneumonectomy:
FDG-avid pleural thickening after pneumonectomy is not uncommon and can persist for years. This thickening is usually fairly uniform in uptake, typically mild to moderately avid.
Unless a focal component of this thickening demonstrates FDG-uptake significantly greater than the remainder of the affected pleura (“you can put your finger on the spot”), the finding is “presumed inflammatory”. Follow up, however, may be warranted.
Infection/Empyema:
Infection/empyema can cause intensely avid pleural thickening. The patient’s clinical history, however, usually leads one to the proper diagnosis in these cases. Follow-up may be required.
Pleural Malignancy:
FDG-avid pleural thickening, in the absence of associated hyperdensity on the CT images (hyperdensity suggests pleurodesis) or a reasonable clinical explanation (e.g. prior pneumonectomy), is highly suggestive of malignancy — typically metastatic disease, lymphoma or mesothelioma. The metabolic activity of this malignant soft tissue is typically greater than liver uptake.
