Imaging diagnosis
Case 315
【Progress】
She was scheduled to take chest CT for evaluation three months later whether opacities including nodules enlarge or not.
【Discussion】
The principal mechanism of absorbing incited foreign body irrespective of infection or non-infection, is that first, macrophages and killer cells phagocyte foreign bodies. In case of infection, antibodies are created by T cells and B cells. Damages of bronchial-alveolar cells are absorbed by macrophages. Reparation process is conducted by reparative T cells and fibroblasts (1, 2). Created fibrin produced by fibrocytes is also phagocyted by macrophages, leaving original circumstances of structure. However, fibrin such as keloid created by myeloblasts remains as permanent probably because of too much connective tissue for macrophages phagocytosis to dispose (1, 2).
Pulmonary granuloma composes of macrophages, lymphocytes, fibrinoid cells such as fibroblasts and myofibroblasts. Macrophages, killer cells, and cytotoxic T cells phagocyte not only foreign bodies but also fibrous tissue fibroblasts create. Fibroblasts and myofibroblasts differentiated by alveolar cell type II creates fibrous tissue probably to block infiltration of incited foreign bodies (3 – 8).
When foreign body is finalized under reparative process by fibroblasts, the intact pulmonary tissue reappears. If not by fibroblasts alone, myeloblasts work to assist fibroblasts, leaving thick connective tissue even if foreign body were absorbed.
In clinical reality, four situations are encountered: first, granulation is completely absorbed. Second, granulation remained. Third, granulation is once absorbed and then, recurred. Fourth, granulation remained and increased or recurred in other area.
It is important to differentiate organizing (granulomatous) pneumonia from inflammatory scar. The remaining of thick trabecular scar after inflammation is created by myofibroblasts while fibrosis absorbed afterwards is created by fibroblasts.
Meanwhile, granulomatous pneumonia whose pathologic findings revealed that it is composed of accumulation of macrophages, lymphocytes and fibroblasts created in various disease (3 – 8). Organizing pneumonia is pathologically defined that granulation tissue occupied in alveolar space and found in respiratory bronchioles or terminal bronchioles. Organizing pneumonia can be absorbed or remained. Radiologically, it appears three patterns: alveolar patchy opacity pattern, interstitial small alveolar patchy opacity pattern, and solid focal mass pattern. Solid mass pattern is challenging to differentiate pulmonary cancer (9, 10).
In our case, one solid mass and alveolar patchy opacity in right lung and interstitial patchy opacity in left lung. The pathogen is not identified. Laboratory test revealed white blood cells count is within normal limits and CRP values elevated. The patient is under observation of follow-up studies whether nodules enlarge or not.
【Summary】
We presented a seventy-two-year-old female for liver dysfunction. Laboratory test revealed white blood cells are within normal limits and CRP values of 7.49 mg/dL. Chest CT demonstrated two small nodules in right lobe and trabecular patchy opacity in left lung, suspicious of organizing pneumonia because of unknown origin. It is borne in mind that granulomatous pneumonia or organizing pneumonia is different from post-inflammatory scar. Post-inflammatory scar is created by myofibroblasts while granulation composes of macrophages, lymphocytes and fibroblasts. Granulomatous pneumonia irrespective of necrosis or non-necrosis occurs in various disease. This term is used in case of arising from unknown origin. Radiologic features are alveolar patchy opacity, interstitial small alveolar patchy opacity and solitary nodules.
【References】
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2023.10.31