ARRS 2022 Abstracts

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E1798. Pneumonic Adenocarcinomas: Imaging Nuances and Clinical Implications
Authors
  1. Palmi Shah; Rush University Medical Center
  2. Daniel L'Heureux ; Rush University Medical Center
  3. Ramya Gaddikeri; Rush University Medical Center
Background
The revised WHO terminology for lung cancers in 2015 saw bronchioloalveolar cell carcinoma (BAC) being reclassified as adenocarcinoma spectrum. One of the radiologic presentations of BAC was consolidation. This unique radiologic presentation is somehow lost in translation following the updated classification. Recognition of the "pneumonic" presentation and unique radiologic features of adenocarcinoma has several clinical implications.

Educational Goals / Teaching Points
Pneumonic adenocarcinoma is often misdiagnosed as an infection delaying treatment. These are commonly mucinous invasive adenocarcinomas, but there can also be non-mucinous adenocarcinomas. At pathology, mucin and lepidic spread is commonly seen. At CT, these appear as consolidations, ground glass large densities, mixed densities, and can show interlobular septal thickening. Aerogenous spread of this tumor can present as ground glass or subsolid nodules, which should not be mistaken for synchronous cancers. For accurate T and M staging, recognition of these metastatic nodules is important. T staging can be challenging, as borders are often indistinct. PET-CT often shows low level of FDG activity. Spread is often limited to the lungs, and these tumors often present with advanced intrathoracic disease. Recurrence can present as multifocal mixed density nodules or consolidations, often mistaken for infection or medication-induced pneumonitis. EGFR and Kras mutations are common. Prognosis is poor.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Unique radiologic presentations of BAC include large consolidations, ground glass opacities, or mixed densities. Patients often present with large tumors and significant intrathoracic spread. Unique features that may be underrecognized include internal dilated airspaces (author observation) and metastases via aerogenous route. Subsolid metastatic nodules are under recognized and often are mis-staged. New multifocal metastatic airspace densities are often mistaken for infection or pneumonitis during treatment. Improving opacities without treatment may simply mean decrease in mucin, which later progresses.

Conclusion
Radiologists are key in suggesting the diagnosis and staging of this unique presentation of lung adenocarcinoma, which is often misdiagnosed or mis-staged at presentation and recurrence, leading to delayed treatment. Understanding the radiologic nuances will assist in more accurate interpretation and enhance patient care.