Pulmonary focal fibrosis associated with microscopic arterio-venous fistula manifesting as focal ground-glass opacity on thin-section CT

Abstract

Background: Focal ground-glass opacity (GGO) on thin-section computed tomography (CT) may be seen in atypical adenomatous hyperplasia (AAH), adenocarcinoma in situ that has recently been renamed from bronchioloalveolar carcinoma (BAC) and various benign conditions.

Case presentation: We report a case of pulmonary focal fibrosis associated with microscopic arterio-venous fistula (AVF), which showed a focal area of GGO on thin-section CT. The patient was a 58-year-old woman with a GGO on thin-section CT which had increased in size over the period of 2 years. Slightly dilated vessels and thickened interlobular septa were also noted around the GGO. It was diagnosed preoperatively as adenocarcinoma in situ and a partial lung resection by video-assisted thoracic surgery (VATS) was performed. Pathological examination yielded a diagnosis of focal fibrosis associated with microscopic AVF.

Conclusion: We speculate that the focal fibrosis was produced by a prolonged congestion due to the AVF and that the dilated vessels and thickening of interlobular septa on thin-section CT related to the AVF. Microscopic AVF may be one of the etiologies of focal fibrosis showing focal GGO on thins-section CT. Dilated vessels and thickened interlobular septa around the GGO might offer a clue to the diagnosis of this disease entity. In addition, it should be noted that focal fibrosis may increase in size.

Figure 1

Chest thin-section CT on admission to our hospital. (a) A thin-section CT at the level of right upper lobe shows a 10-mm round, well-defined GGO nodule (arrow). There are slightly dilated veins or thickening of the interlobular septa (arrow heads). (b) Similar findings are seen also on the slice just above the focal GGO (arrow heads).

Figure 2

Screening chest CT at 2 years before CT examination at our hospital. A 7mm slice thickness CT shows a faint pure GGO in the right upper lobe (arrow), which is smaller than that of Figure 1.

Figure 3

Histopathology of the resected lung tissue. (a) Photomicrograph (hematoxylin-eosin stain; original magnification, ×2) shows a focal area of alveolar wall thickening with preservation of the intraalveolar airspaces, consistent with the focal GGO on thin-section CT (arrow). Partial collapse of this lesion is due to an artifact during the process of specimen production. (b) Photomicrograph (hematoxylin-eosin stain; original magnification, ×10) shows alveolar wall thickening with fibrosis, and congestion(arrows). Alveolar bronchiolizations are also seen (arrowheads). (c) Photomicrograph (elastica Masson stain; original magnification, ×4) near the focal fibrosis shows dilated arterioles (asterisk) with markedly thickened walls, one of which have resulted in luminal obliteration (black arrow), as well as dilated venules (white arrows). A transition from arteriolar wall to venular one is seen, suggesting a direct communication between them (arrow head).