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Clinicopathologic Features of Isolated AFOP Nodules Radiologically Mimicking Malignancy in Post COVID-19 Patients: A
Massimiliano Mancini1, Lavinia Bargiacchi2, Gisella Guido3
1Morphologic and Molecular Pathology Unit, St. Andrea University Hospital, Sapienza University of Rome, 00189 Rome, Italy.
Abstract:
Background/Objectives: Acute Fibrinous and Organizing Pneumonia (AFOP) is a rare pulmonary condition histologically characterized by intra-alveolar fibrin deposition and organizing pneumonia without hyaline membranes. This study aims to describe the clinicopathologic and radiologic features of isolated AFOP nodules presenting as solitary pulmonary nodules (SPNs) mimicking malignancy in patients with recent COVID-19 infection. Methods: We retrospectively analyzed consecutive cases of histologically confirmed AFOP (n = 20) and organizing pneumonia (OP; n = 119) presenting radiologically as SPNs suspicious for malignancy from January 2021 to December 2023. Clinical data, COVID-19 status, radiologic features (including nodular characteristics, ground-glass opacity [GGO], and consolidation), and histopathological findings were collected and analyzed. Digital image analysis quantified the intra-alveolar fibrin content. Results: AFOP nodules showed a significant association with previous COVID-19 infection compared to OP (55% vs. 0.8%, p < 0.001). Radiologically, AFOP lesions were predominantly located in the upper lobes, frequently exhibiting a mixed pattern of GGO and consolidation within solitary nodules (8-28 mm diameter), distinctly differing from the predominantly lower-lobe homogeneous consolidations in OP. Histologically, AFOP was defined by prominent intra-alveolar fibrin "balls," correlating significantly with radiological consolidation patterns (r = 0.991, p < 0.05). Regions of consolidation demonstrated higher fibrin contents compared to areas of predominant GGO. Conclusions: Isolated AFOP nodules presenting as SPNs post-COVID-19 infection strongly mimic malignancy radiologically, highlighting the necessity for multidisciplinary diagnostic approaches integrating radiological and histopathological data to avoid unnecessary interventions. Recognition of this rare but distinctive clinical entity is essential for appropriate patient management.
Insights
Acute Fibrinous and Organizing Pneumonia (AFOP) nodules after COVID-19 infection can mimic lung cancer on imaging. Early recognition of these AFOP nodules is crucial for accurate diagnosis and avoiding unnecessary treatments.
Area of Science:
- Pulmonary Pathology
- Radiology
- Infectious Disease Complications
Background:
- Acute Fibrinous and Organizing Pneumonia (AFOP) is a rare pulmonary condition.
- AFOP is characterized by intra-alveolar fibrin and organizing pneumonia.
- This study focuses on AFOP nodules mimicking malignancy post-COVID-19.
Purpose of the Study:
- To describe clinicopathologic and radiologic features of AFOP nodules.
- To investigate AFOP nodules presenting as solitary pulmonary nodules (SPNs) post-COVID-19.
- To differentiate AFOP from organizing pneumonia (OP) in SPN context.
Main Methods:
- Retrospective analysis of 20 AFOP and 119 OP cases with SPNs.
- Review of clinical, COVID-19 status, radiologic, and histopathologic data.
- Digital image analysis for intra-alveolar fibrin quantification.
Main Results:
- AFOP nodules significantly associated with prior COVID-19 (55% vs 0.8%).
- AFOP lesions showed upper lobe predominance, mixed GGO/consolidation patterns.
- Intra-alveolar fibrin "balls" correlated with consolidation and higher fibrin content.
Conclusions:
- AFOP nodules post-COVID-19 can radiologically mimic lung malignancy.
- Multidisciplinary approach integrating imaging and pathology is vital.
- Recognizing this entity is essential for appropriate patient management.
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