Ann Thorac Surg 2008;85:1432-1434. doi:10.1016/j.athoracsur.2007.10.031
© 2008 The Society of Thoracic Surgeons
Case Reports
Pseudocavitating Bronchioloalveolar Carcinoma Followed Over a Decade
Jason P. Shaw, MDa,*,
Pablo A. Bejarano, MDb,
Richard J. Thurer, MDa
a Department of Surgery, Division of Cardiothoracic Surgery, University of Miami Miller School of Medicine, Miami, Florida
b Department of Pathology, University of Miami Miller School of Medicine, Miami, Florida
Accepted for publication October 1, 2007.
* Address correspondence to Dr Shaw, Department of Surgery, Division of Cardiothoracic Surgery, University of Miami Miller School of Medicine, PO Box 016960 (R-114), Miami, FL 33010 (Email: jason.shaw{at}mssm.edu).
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Abstract
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A 38-year-old woman with bronchioloalveolar carcinoma (BAC) had a slow-growing cavitary nodule for nearly a decade. When she was hospitalized because of pneumonia 9 years earlier, a chest computed tomography scan showed a 1.5-cm cavitary right upper lobe nodule. At 1, 3, and 9 years computed tomography scans showed slow growth of the nodule to 2.4 cm, corresponding to a volume doubling time of 1494 days. Thoracoscopic biopsy and lobectomy were performed. Pathologic analysis revealed a well-differentiated mucinous BAC (T1N0M0). Pseudocavitation in solitary BAC is rare. A longer period of surveillance may be required to rule out malignancy in this setting. Surgical resection remains the mainstay of therapy.
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Introduction
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With more widespread use of computed tomography (CT) of the lung, small bronchioloalveolar carcinomas (BACs) are being diagnosed with increasing frequency. Bronchioloalveolar carcinomas are generally thought to have a more indolent course than other subtypes of adenocarcinoma of the lung. While CT appearance varies, the presence of BAC as a solitary cavitary nodule is rare. We report the case of a slow-growing BAC in a young woman that highlights the importance of prolonged surveillance or resection when BAC is included in the differential diagnosis.
A 38-year-old woman with nonpleuritic chest pain and a long-standing right upper lobe cavitary lesion, with a 3 pack-year smoking history, was referred for thoracic surgical evaluation. Nine years previously the patient had been hospitalized because of pneumonia involving the posterior segment of the right upper lobe. Results of tuberculin skin testing were negative. When a chest radiograph at 6-month follow-up showed a persistent mass, a CT scan of the chest was obtained, which revealed a 1.5-cm rounded lesion with central lucency (Fig 1A). Bronchoscopy performed 1 year after initial presentation was nondiagnostic. A chest CT scan obtained 9 years after initial presentation demonstrated the lesion in the right upper lobe measuring 2.4 cm. A fluorodeoxyglucose positron emission tomography scan demonstrated no uptake. Thoracoscopic biopsy followed by lobectomy with lymph node dissection was performed. Pathologic analysis revealed a 2.5-cm well-differentiated mucinous BAC (T1N0M0) (Figs 2, 3).
The patient had an uneventful hospital course and was discharged on postoperative day 4.
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Fig 1. (A-D) Computed tomography scans of the chest obtained at 6 months and at 1, 3, and 9 years, respectively, after initial presentation.
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Fig 3. At histologic analysis, tumor cells were noted growing along the alveolar septa in a lepidic pattern and the alveolar spaces were filled with mucin (hematoxylin-eosin stain, original magnification x200).
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During nearly a decade, CT scans had been obtained at various institutions, at 6 months and at 1, 3, and 9 years after initial presentation (Figs 1A-D). Review of the scans revealed a largest tumor diameter of 1.5 cm, 1.5 cm, 1.6 cm, and 2.4 cm, respectively, suggesting tumor stability at 1 year. However, calculation of tumor volume from each CT scan (V = 
/6 x ab2, where a is the largest diameter and b is the largest diameter perpendicular to a) showed an increase in tumor volume at each interval, with volumes of 1.3 cm3, 1.4 cm3, 1.8 cm3, and 5.6 cm3, respectively. Tumor volume doubling time (VDT) at each interval was calculated using the modified Schwartz equation (VDT = [t x log 2] ÷ log[Vt/Vo]), where t is the interval in days between 2 scans, Vo is tumor volume on the initial CT scan, and Vt is tumor volume on subsequent CT scans) and revealed a VDT of 1,651, 2,643, and 1,261 days, respectively [1]. Tumor volume increased slowly over the first 3 years, with a subsequent increase in growth rate, although at all intervals the VDT was long. Overall VDT (calculated from the first and last scans) was 1,494 days.
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Comment
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Bronchioalveolar carcinoma is an increasingly common primary lung neoplasm, although data about its incidence and prognosis are confounded by difficulties in case definition. A subtype of adenocarcinoma of the lung, BAC may have a more indolent course than other types of non–small cell lung cancers. It is classified pathologically as mucinous, nonmucinous, and mixed subtypes.
Bronchioalveolar carcinoma seen as a solitary cavitary nodule is rare [2, 3]. Several mechanisms have been proposed to explain the cavitary appearance of a lesion on CT scans, that is, so-called pseudocavitation. One theory postulates that multiple oval areas of low attenuation mimic small cavities. Others suggest that the cavitary appearance results from a process analogous to that seen on an air bronchogram: proliferation of tumor cells along the alveolar walls without disruption of lung architecture and with maintenance of alveolar patency [4]. Given the mucinous histologic findings in this case, it is possible that the low attenuating, mucin-containing airspace within the tumor produced the appearance of a central cavity on CT scans and at gross pathologic examination.
Differentiating pseudocavitary BAC from other causes of solitary cavitary nodules is challenging. The differential diagnosis includes tuberculosis, fungal infections, other lung cancers, metastases, necrotic rheumatoid nodules, Wegener granulomatosis, and eosinophilic granuloma. Although our patient’s age, sex, minimal smoking history, and presentation to several different institutions during nearly a decade likely all contributed to the delay in diagnosis, the initial lesion diameter of greater than 1 cm and the subsequent increase in size should have raised suspicion of malignancy. The lesion was followed up closely during the first 3 years, at which point it was thought to be benign. However, when BAC is included in the differential diagnosis, surveillance for as long as 5 years or longer may be required to rule out malignancy.
Some studies suggest a worse prognosis for BAC of the mucinous subtype, with 5-year survival as low as 59% [5]. In addition, mucinous BAC cells may be more likely to detach from the underlying basement membrane and spread aerogenously [6]. In contrast, our calculated VDT of 1494 days, even longer than the mean of 851 days in women with BAC in one study [1], suggests an extremely indolent course. This VDT far exceeds the 400-day threshold used by some authors to define overdiagnosis in the context of lung cancer CT screening trials [7]. However, it is important to remember that these numbers may have a quite different meaning for the lifespan of a heavy smoker older than 60 years compared with our young, otherwise healthy patient. Until molecular diagnostic procedures enable more accurate prediction of prognosis, controversy about the clinical significance of small BACs and the extent of resection may continue, but surgery remains the mainstay of treatment.
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Acknowledgments
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Dr Caralee Caplan-Shaw provided editorial assistance.
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References
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Abstract
Introduction
