E3459. Benign Atypical Pulmonary Cysts Mimic Cancer on Lung Screening CT Imaging
  1. Kim Sandler; Vanderbilt University Medical Center
  2. Zachary Shaff; New York Medical College
  3. Alexis Paulson; Vanderbilt University Medical Center
  4. Sarah Valenti; Vanderbilt University Medical Center
  5. Shanna Joyner; Vanderbilt University Medical Center
  6. Emily lippincott; Vanderbilt University Medical Center
Screening for lung cancer with low-dose CT (LDCT) is currently recommended for individuals ages 50-80 with a 20 or more pack-year history of tobacco use who are either currently smoking or quit within the past 15 years. Lung-RADS is a standardized system for the reporting and management of findings on lung cancer screening examinations. In 2022, new recommendations were added for atypical pulmonary cysts. Lesions with cystic components provide a unique challenge as cancer is often diagnosed at a later stage than with noncavitary lesions, however, these findings may also result from benign disease. Atypical cysts can be categorized as a Lung-RADS 3 (probably benign) if there is a growing cystic component of a thick-walled cyst, or Lung-RADS 4 (Suspicious) for a thick-walled or multilocular cyst at baseline, or a thin- or thick-walled cyst that becomes multilocular. In this exhibit, we provide examples of 5 unique lung screening examinations with atypical pulmonary cysts. These lesions were investigated with tissue sampling, and all were found to be benign. Although each lesion warranted further evaluation to exclude malignancy, these cases demonstrate the difficulty in interpreting lung screening examinations with atypical pulmonary cysts.

Educational Goals / Teaching Points
The goal of this educational exhibit is to demonstrate suspicious atypical pulmonary cysts found on LDCT for lung screening. Cystic lesions present a unique challenge for radiologists as their complex appearance can delay a cancer diagnosis but can also result from benign disease. The categorization of cystic lesion with the Lung-RADS lexicon is a new feature of the reporting system. Tissue sampling in these cases either confirmed infection or suggest a resolving infectious or inflammatory process.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
All CT imaging was obtained for lung cancer screening utilizing a low-dose CT protocol without IV contrast. Imaging findings for each examination include an atypical pulmonary cyst categorized as Lung-RADS 4 lesion. These atypical pulmonary cysts were ultimately determined to be benign following tissue sampling and include multilocular right upper lobe cyst and thick-walled cyst in left upper lobe, biopsy negative for malignancy (likely infection). Right upper lobe thick-walled cavitary lesion, biopsy diagnostic of histoplasmosis. Left upper lobe thick-walled cavitary lesion, biopsy negative for malignancy, likely scar from prior infection. Large right upper lobe cavitary lesion, biopsy diagnostic of tuberculosis, and left upper lobe thick-walled cyst found to be FDG avid on PET, biopsy negative for malignancy, likely resolving infection.

Atypical pulmonary cysts provide a unique challenge on lung screening examinations. These lesions are often categorized as suspicious as they mimic malignancy. Radiologists may be able to improve interpretation and differentiation of benign and malignant atypical cysts through image and data sharing.