British Journal of Radiology (2008) 81, e11-e12
© 2008 British Institute of Radiology
doi: 10.1259/bjr/14240787
Pulmonary metastatic microangiopathy of colon cancer presenting as a "tree in bud" pattern
S Bosmans, MD1,
B Weynand, MD2 and
E Coche, MD, PhD1
Departments of 1 Radiology and 2 Anatomo-pathology, Cliniques Universitaires St-Luc, Université Catholique de Louvain, Av Hippocrate 10, 1200 Brussels, Belgium
Correspondence: Emmanuel Coche, Department of Radiology, St Luc University Hospital, Catholic University of Louvain, Av Hippocrate 10, 1200 Brussels, Belgium. E-mail: coche{at}rdgn.ucl.ac.be
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Abstract
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The authors report an unusual case of a "tree in bud" pattern of vascular origin caused by colon cancer metastases. A 60-year-old man presented for routine follow-up of a colon tumour resected surgically 15 years previously. Clinical examination, laboratory tests, including carcino-embryonic antigen and inflammatory parameters, and chest radiograph were normal. Multislice CT of the lungs revealed the presence of several "tree in bud" opacities. The connection to the pulmonary arteries was well depicted by reformatted maximal intensity projection images. Biopsy of some of the nodules was characterized by mucinous material and neoplastic cells within the small vessels, consistent with metastases from the known colon adenocarcinoma.
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Introduction
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The "tree in bud" (TIB) pattern is a finding seen on thin-section CT of the lungs. It occurs because of the connection between peripheral centrilobular nodules and linear and branching opacities, and has been almost exclusively described in small airways disorders. We report a case of TIB patterns in relation to neoplastic pulmonary emboli from a colon adenocarcinoma.
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Case report
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A 60-year-old man presented for routine follow-up of a colon tumour resected surgically 15 years previously. In addition, a right liver lobe resection for a solitary liver metastasis was performed 5 years previously. Clinical examination was normal. Laboratory tests including carcino-embryonic antigen (CEA) and inflammatory parameters were within normal limits. Chest radiograph was unremarkable. Enhanced 16-slice CT (MX brilliance 16; Philips Medical systems, Cleveland, OH) was performed with the following parameters: 16 x 0.75 mm, 1 mm interval reconstruction, 120 kV and 150 mAs. Axial slices revealed small lung nodules located in a sub-pleural location. Thin-slab maximal intensity projection slices demonstrated arborescent linear structures connected to the peripheral pulmonary arteries and representing a TIB pattern (Figure 1a,b
). Fluorodeoxyglucose (FDG) positron emission tomography revealed hypermetabolic nodules corresponding to the lung nodules. Open lung biopsy was performed and pathological examination showed the nodules to be characterized by the presence of mucinous material lying free in the peripheral pulmonary arteries, lymphatics and veins. These "lakes" contained a few neoplastic cells with basophilic cytoplasm and atypical nuclei (Figure 1c).
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Figure 1. 60-year-old woman with a metastatic pulmonary microangiopathy of a colon cancer. (a) Thin-slab maximal intensity projection (MIP) frontal reformatted CT images (at lung window settings) show multiple linear branching opacities connected to the peripheral pulmonary arteries in both the right-lower lobe and left-upper lobe (straight arrows). This represents the "tree in bud" sign, in relation to the multiple endovascular tumour emboli. Note a right liver lobe resection related to previous surgery for a liver metastasis. (b) Thin-slab MIP axial reformatted CT focused on the right lung illustrates, at lung window settings, the arborescent aspect of the vascular abnormalities (straight arrows). (c) Photomicrograph of the open lung biopsy, which shows a vessel lumen occluded by mucus (left-hand side; arrowhead) and another vessel containing neoplastic cells together with mucus and an organizing thrombus (right-hand side; arrows) (left-hand image: x2.5, right-hand image: x20).
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Discussion
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The TIB pattern, observed on thin-section CT images of the lung, consists of peripheral (within 3–5 mm of the pleural surface), small (2–4 mm in diameter) centrilobular nodules connected to linear branching opacities [1].
When the TIB pattern was initially described, it was only in relation to small airway disorders [1–3]; however, it has now also been found in a large number of lung conditions related to infectious disorders (e.g. those involving bacterial, mycobacterial, viral, parasitic and fungal agents). On pathological examination, the TIB pattern is the result of bronchiolar luminal impaction (with mucus, pus or fluid), bronchial dilatation and wall thickening, which demarcates the normally invisible branching course of the peripheral airways.
Recently, Tack et al [4] and Franquet et al [5] reported cases of pulmonary tumour thrombotic microangiopathy that were manifest on thin-section CT as diffuse TIB opacities. This pattern was reportedly observed in an abdominal desmoplastic small-round-cell tumour [4] and a gastric carcinoma [5].
There are two different pathogenic mechanisms accounting for the appearance of a TIB pattern on thin-section CT in patients with pulmonary tumour embolism. The first mechanism is the filling of the centrilobular arteries by tumour cells. The second is thrombotic microangiopathy, characterized by fibrocellular intimal hyperplasia of small pulmonary arteries induced by tumour microemboli.
In these neoplastic cases, histology reveals arterial occlusion by tumour cells, peripheral arterial dilatation and widespread fibrocellular intimal hyperplasia.
In the present case, because of the lack of clinical and biological signs of infectious or metastatic disease and given the long recurrence-free history of the patient despite their history of cancer, a biopsy of the TIB pattern images was obtained from the right-lower lobe. Microscopic examinations revealed arterial occlusion by mucoid material containing neoplastic cells, consistent with a metastasis from the known colon adenocarcinoma, along with cellular intimal proliferation.
Received for publication June 23, 2006.
Revision received August 11, 2006.
Accepted for publication October 2, 2006.
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References
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- Tack D, Nollevaux MC, Gevenois PA. Tree-in-bud pattern in neoplastic pulmonary emboli. AJR Am J Roentgenol 2001;176:1421–2.[Free Full Text]
- Franquet T, Gimenez A, Prats R, Rodriguez-Arias JM, Rodriguez C. Thrombotic microangiopathy of pulmonary + tumors: a vascular cause of tree-in-bud pattern on CT. AJR Am J Roentgenol 2002;179:897–9.[Free Full Text]
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Abstract
Introduction
