Yonago Acta medica 2007;50:41–44

Thoracoscopic Resection of an Anterior MediastinalBronchogenic Cyst
Shinji Fujioka, Tomohiro Haruki, Yoshin Adachi, Ken Miwa, Yuji Taniguchi, Hiroshige
Nakamura and Hisao Ito*
Division of Thoracic Surgery, Clinical Department of Surgery, Tottori University Hospital, Yonago
683-8504 and *Division of Organ Pathology, Department of Microbiology and Pahology, School ofMedicine, Tottori University Faculty of Medicine, Yonago 683-8503 Japan

We report a very rare case of anterior mediastinal bronchogenic cyst, successfully resected by thoracoscopic surgery. A 78-year-old female was noted as having an abnormal shadow on her chest X-ray during a routine medical checkup. Chest CT revealed acystic tumor in the anterior mediastinum. A thymic cyst was suspected after a detailed
examination and thoracoscopic surgery was performed. A cystic tumor containing yellowish-white mucus measuring 46 × 33 × 19 mm in size was successfully removed. Calciﬁcation was also observed in the cyst wall. Pathologically, the tumor was characterized
by a ciliated columnar epithelial lining, and was subsequently diagnosed as a bronchogenic cyst. Although they may be rare, bronchogenic cysts should also be considered in
the evaluation of cystic tumors in the anterior mediastinum.
Key words: anterior mediastinum; bronchogenic cyst; thoracoscopic resection
cancer and a ruptured cerebral aneurysm with
subarachnoid hemorrhage eight years ago. No
particular abnormalities were found in hematological or biochemical examinations. Chest CT atour hospital detected an oval tumor mass 30 × 20
mm in size with a clear boundary in the anterior
mediastinum bounded posteriorly by the ascending aorta. The tumor showed no contrast enhancement but calciﬁcation was observed in partof the wall (Fig. 1). Chest MRI examination was
not conducted because of the previous clipping
surgery for cerebral aneurysm. The preoperative
diagnosis was a thymic cyst and thoracoscopic
resection was performed. The tumor was present
in the anterior mediastinum, bordering on the anterior surface of the ascending aorta, and included
the surrounding thymic fat. It was easily removed
through a 4-port operation. Surgery took 56 minwith a minimal amount of bleeding. After it wasremoved, the tumor was measured at 46 × 33 ×Bronchogenic cysts are rare mediastinal cystic tumors accounting for 4.5% to 5% of all mediastinal
tumors (Martinod et al., 2000; Kori et al., 1993)
and their occurrence in the anterior mediastinum
is very rare. We describe a case of anterior mediastinal bronchogenic cyst, which was successfully
removed by thoracoscopic surgery.

Patient Report
A 78-year-old female was noted as having an abnormal shadow on her chest X-ray during a routine medical checkup. She subsequently visited
a neighborhood hospital where chest CT revealedno lesion at the site shown by the previous chest
X-ray, but disclosed a tumor mass in the anterior
mediastinum. She was referred to our department
for evaluation and therapy. There were no subjective symptoms. She had had operations for colon

Abbreviations: CT, computed tomography; MRI, magnetic resonance imaging; VATS, video-assisted thoracoscopic surgery

41

S. Fujioka et al.

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Fig. 2. Macroschopic appearance of the cut surface of theremoved tumor, showing the internal surface of the tumor
measuring 46 × 33 × 19 mm. Yellowish-white, slightly
cloudy, viscous contents within the cyst have drained out.
Calciﬁcation is observed in part of the wall (arrow).

Fig. 1. Chest contrast CT. In the anterior of the ascending aorta (b), an oval tumor mass (*) with a clear boundary is detected. There is no contrast enhancement in thetumor, and calciﬁcation is observed in part of the wall (arrow). a: superior vena cava, b: ascending aorta, c: aortic
arch, d: descending aorta.

19 mm and contained yellowish-white, slightly
cloudy, viscous contents on the cut surface (Fig.
2). During pathological examination, the internalsurface of the cyst was covered with ciliated columnar epithelial cells, and mucous glands, cartilage, and smooth muscles were observed in thecyst wall (Fig. 3). The tumor was diagnosed asa bronchogenic cyst and the postoperative course
was good.

Discussion
More than 90% of bronchogenic cysts occur inthe mediastinum and lungs, mostly in the former (77%) (Zhang et al., 2003; St-Georges etal., 1991). Their occasional occurrence in thediaphragm, peritoneum or subcutaneous tissue��Fig. 3. Pathological ﬁndings of the resected tumor. The tumor is characterized by a bronchial epithelial lining andthe presence of cartilage in its wall. The cartilage (a), smooth muscles (b) and mucous glands are also observed in
the cyst wall (hematoxylin and eosin staining). Bar = 100 μm.

42Thoracoscopic resection of a mediastinal cyst

The differential diagnosis of anterior mediastinal cystic tumors includes thymic cysts andmature cystic teratomas. Thymic cysts show athin and translucent wall, and no contrast enhancement on chest CT. Mature cystic teratomas
have distinct, sharply delineated walls which areoften calciﬁed and thickened (Rosai, 1996). Surgery is not always needed for asymptomatic casesof bronchogenic cysts. However, there is at least
one report describing a cyst wall showing somemalignant change into glandular cancer (Sullivanet al., 1999). Thus, thoracoscopic surgery has
now been widely accepted for the treatment ofbronchogenic cysts. Although thymic cysts aremost frequent among cystic tumors in the anterior
mediastinum, surgeons should consider the possibitlity of bronchogenic cysts in the differentiationof those tumors.

has also been reported as ectopic bronchogenic
cysts (Kim et al., 2001; Hamaguchi et al., 2002;
Okada et al., 2006). Concerning the origin ofectopic bronchogenic cysts, two theories arewidely accepted. The ﬁrst theory is sequestrationor budding of the tracheal primordia at the timeof the development of the sternum. The second
theory is the abnormal migration of the pinchedoff tracheobronchial epithelium to the ectopic
areas, prior to the complete fusion of the sternal
mesenchymal bars (Kim et al., 2001). The present case may be explained by the second theory.
Maier classiﬁes bronchogenic cysts into ﬁve types
based on the sites of occurrence: paratracheal(type I); tracheal bifurcation (type II); hilar (typeIII); paraesophageal (type IV) and others (type V)(Maier, 1948). Bronchogenic cysts of the anterior
mediastinum are classiﬁed as type V. Their occurrence is most frequent in the middle mediastinum, including types I, II, and III, accounting for
40% of all mediastinal bronchogenic cysts (Haraet al., 2001).
Out of 68 cases of bronchogenic cysts appearing in areas other than the middle mediastinum, only 3 cases (3.4%) occurred in the anterior
mediastinum (type V) (Kagotani et al., 1986).
Our survey of previous Japanese cases of bronchogenic cysts revealed only 11 cases in the anterior mediastinum (Kagotani et al., 1986; Taniwaki
et al., 1997; Takasuna et al., 1999; Takei, 2005).
Thus, anterior mediastinal bronchogenic cysts arevery rare.
Generally, CT findings of bronchogenic
cysts show a higher density than water in mostcases (75%), and contrast enhancement in thecyst wall (33%), although this may not always betypical (Hara et al., 2001). The chest CT in ourcase showed a higher density than water, but nocontrast enhancement. T2-weighted MRI images
often show signiﬁcantly homogenous high signals.
So MRI is useful for diagnosis of cystic tumors(Hara et al., 2001). Chest MRI was not conductedin our case because the patient had clipping surgery for a ruptured cerebral aneurysm 8 years
previous.

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Received March 22, 2007; accepted May 29, 2007
Corresponding author: Shinji Fujioka, MD44