AJR 2004; 182:79-80
© American Roentgen Ray Society
Squamous Cell Carcinoma Coexisting in Rounded Atelectasis: Diagnostic Pitfalls
T. Nakazono1,
Y. Nakamura1,
T. Satoh2,
T. Sakuragi3,
Y. Sakao3 and
S. Kudo1
1 Department of Radiology, Saga Medical School, 5-1-1 Nabeshima, Saga City, Saga
849-8501, Japan.
2 Department of Pathology, Saga Medical School, Saga 849-8501, Japan.
3 Department of Cardiovascular and Thoracic Surgery, Saga Medical School, Saga
849-8501, Japan.
Received April 24, 2003;
accepted after revision July 2, 2003.
Address correspondence to T. Nakazono
(nakazot{at}post.saga-med.ac.jp).
Introduction
Rounded atelectasis is an infolding of the lung parenchyma associated with
focal pleural thickening. CT findings are usually characteristic of the
disease, and in many cases further examination or biopsy is not necessary.
Coexistence of rounded atelectasis and lung cancer is rare; a review of the
literature reveals only one letter published in an English-language journal
[1]. We report a case of
squamous cell carcinoma in rounded atelectasis as revealed by CT and
histologic findings.
Case Report
A 70-year-old man with a history of heavy smoking and myelodysplastic
syndrome was admitted to our hospital complaining of hemosputum. Chest
radiography showed a mass in the lower lobe of the right lung.
Hematologic evaluation showed pancytopenia and was negative for serum tumor
markers. CT at 30 sec after injecting contrast material revealed a 4.0 x
3.0 cm inhomogeneous mass with a sharp margin in the right lower lobe.
Thickening of the pleura was seen adjacent to the mass
(Fig. 1A). The bronchus and the
pulmonary vessels were curved and continued into the mass, presenting the
comet-tail sign (Fig. 1B). The
CT findings were compatible with a diagnosis of rounded atelectasis, but
bronchoscopy was performed because of the patient's hemosputum. A
transbronchial lung biopsy suggested squamous cell carcinoma; thus, a right
lower lobectomy was performed. Macroscopically, the visceral pleurae of the
right lower lobe were thickened and markedly fibrous. The mass consisted of
whirllike collapsed lung parenchyma compatible with rounded atelectasis. A
whitish tumor measuring 2.0 x 1.5 cm was located in the rounded
atelectasis (Fig. 1C).
Microscopically, the tumor consisted of solid-sheet nests of severely atypical
squamous cells with keratin formation and intercellular bridges. There was no
evidence of necrosis in the tumor. The histopathologic diagnosis was
moderately differentiated squamous cell carcinoma. Fibrosis of the visceral
pleura and the lung parenchyma was seen near the tumor nests
(Fig. 1D). The tumor nests were
surrounded by rounded atelectasis, and there was no bronchial obstruction
caused by the tumor. Extensive atelectasis and fibrosis suggested that the
rounded atelectasis had been present chronically and that lung cancer had
developed coincidentally within it.
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Fig. 1A. —70-year-old man with squamous cell carcinoma coexisting in
rounded atelectasis. Contrast-enhanced CT scan (mediastinal window setting)
shows subpleural mass (arrows) in right lower lobe. Mass has distinct
margin and shows inhomogeneous enhancement. Focal pleural thickening
(arrowheads) is seen adjacent to mass.
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Fig. 1B. —70-year-old man with squamous cell carcinoma coexisting in
rounded atelectasis. CT scan (lung window setting) shows that bronchus and
pulmonary vessels (arrows) of right lower lobe are curved and
continue to mass, presenting comet-tail sign.
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Fig. 1C. —70-year-old man with squamous cell carcinoma coexisting in
rounded atelectasis. Photograph of macroscopic specimen shows thickening of
visceral pleura (large arrows) and whirllike collapsed lung
parenchyma (small arrows) compatible with rounded atelectasis.
Whitish tumor (arrowheads) is located in rounded atelectasis.
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Fig. 1D. —70-year-old man with squamous cell carcinoma coexisting in
rounded atelectasis. Photomicrograph of histopathologic specimen shows marked
fibrosis of visceral pleura and lung parenchyma (arrows) near tumor
nests (arrowheads). (H and E, x4)
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Discussion
Rounded atelectasis is a distinct form of atelectasis characteristically
associated with focal pleural thickening. Atelectasis is usually asymptomatic
and frequently seen in patients with asbestosis
[2]. Rounded atelectasis is
thought to result from infolding of the lung in the presence of pleural fluid
and fibrinous pleuritis [2]. On
chest radiographs, the abnormality is seen as a homogeneous round, oval, or
wedge-shaped subpleural mass in the lower lobes
[3]. CT shows a sharply
margined and homogeneous subpleural mass and volume loss in the affected lung.
Associated findings on CT include adjacent pleural effusion or thickening,
incurving vessels and bronchi (comet-tail sign), acute angles with pleura, and
sharp lateral margins with a poorly defined central margin
[4,
5].
Diagnostic accuracy for rounded atelectasis is high when most
characteristic CT features are present, and in such cases further examination
or biopsy is not necessary. However, O'Donovan et al.
[5] compared CT features of
rounded atelectasis with rounded atelectasis look-alikes, including lung
cancers, and reported that the radiologic diagnosis is imperfect. In the
present case, CT findings were compatible with rounded atelectasis, but we
were unable to detect lung cancer in the collapsed lung using CT alone.
Contrast enhancement during the first minutes after injection has been
reported to be higher in rounded atelectasis than in malignant lung tumors
[6]; we obtained CT images at
30 and 90 sec after injecting contrast material, but lung cancer was not
detected. Rounded atelectasis usually has homogeneous enhancement
[6], and inhomogeneous
enhancement of the mass may be atypical for rounded atelectasis in our case.
Rounded atelectasis is reported to be not metabolically active on positron
emission tomography (PET) [7].
PET may be useful for differential diagnosis of atypical rounded atelectasis
and lung cancer.
Coexistence of rounded atelectasis and lung cancer is rare; we could find
only one such case in the literature
[1]. Fraser et al.
[2] described the coexistence
of rounded atelectasis and lung cancer to be rare and recommended careful
radiographic follow-up rather than immediate biopsy or surgery for patients
with CT findings suggestive of typical rounded atelectasis.
Our patient was admitted with hemosputum, an unusual symptom in rounded
atelectasis that led to the further diagnosis of squamous cell carcinoma. This
case outcome suggests that follow-up of all clinical findings is important in
treating patients with rounded atelectasis.
References
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AJR 1980;134:225
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- O'Donovan PB, Schenk M, Lim K, Obuchowski N, Stoller JK. Evaluation
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Introduction
Case Report
