Management of Stable Pleural-Based Opacities Over One Year
For pleural-based opacities that have remained stable for one year, no further diagnostic evaluation or follow-up imaging is required, as these findings most likely represent benign entities such as apical scarring, perifissural lymph nodes, or dependent atelectasis. 1
Characterization of Stable Pleural-Based Opacities
The Fleischner Society guidelines specifically address pleural-based opacities and provide clear guidance on their benign nature when certain morphologic features are present:
Apical scarring is extremely common and may have a nodular appearance on transverse CT images, with suggestive features including pleural-based configuration, elongated shape, straight or concave margins, and presence of similar adjacent opacities 1
Perifissural nodules represent intrapulmonary lymph nodes and typically appear triangular or oval on transverse images with a flat or lentiform configuration on sagittal/coronal reconstructions and a fine linear septal extension to the pleura 1
When small nodules have perifissural or juxtapleural location with morphology consistent with intrapulmonary lymph nodes, follow-up CT is not recommended even if the average dimension exceeds 6 mm 1
In the NELSON Lung Cancer Screening Trial, 20% of nodules were classified as perifissural, and while 16% grew during the study, none were malignant 1
Critical Decision Points for Stability Assessment
The two-year stability threshold is the key determinant for management:
Solid indeterminate nodules that have been stable for at least 2 years require no additional diagnostic evaluation 1
Review on coronal or sagittal reconstructed images is helpful in characterizing pleural-based findings to distinguish scars from true nodules 1
Stability over one year strongly suggests benign etiology, and your findings have already exceeded the typical observation period needed for most concerning lesions 1
High-Risk Features That Would Change Management
Even with stability, certain morphologic features warrant continued surveillance or investigation:
Spiculated borders, displacement of adjacent fissure, or history of cancer increase the possibility of malignancy and should prompt follow-up examination in 6-12 months 1
Irregular or spiculated margins, upper lobe location, and larger nodule size are high-risk features that would justify continued monitoring 1
Pleural-based masses (rather than small opacities) with concerning features such as rib erosion require tissue diagnosis via percutaneous biopsy or FDG-PET evaluation 1
Excluding Reversible Dependent Opacities
Before concluding these are stable pleural-based lesions, confirm they are not positional artifacts:
Focal dependent pleural thickenings in posterior and basal locations can mimic pleural plaques but may represent physiological focal accumulation of lymphatic fluid 2
Additional low-dose CT acquisition in prone position should be performed for focal pleural thickening in dependent and basal locations to exclude reversible findings 2
In one series, 144 of 152 posterior lower lobe pleural thickenings completely disappeared on prone imaging 2
Common Pitfalls to Avoid
Do not confuse perifissural nodules with malignant lesions - their specific morphology (triangular/oval shape with flat configuration and septal extension) indicates benign intrapulmonary lymph nodes that require no follow-up 1
Do not overlook the importance of multiplanar reconstruction - coronal and sagittal images are essential for proper characterization of pleural-based opacities and distinguishing scars from nodules 1
Do not apply aggressive follow-up protocols to clearly benign-appearing pleural-based opacities - this leads to unnecessary radiation exposure and patient anxiety without improving outcomes 1
Do not ignore high-risk morphologic features even with stability - spiculated borders or fissural displacement warrant 6-12 month follow-up regardless of prior stability 1