Thoracic Oncology NetWork Online Puzzler - August 2009

Diagnoses and Discussion

Diagnosis: Bronchioalveolar carcinoma

Bronchioalveolar carcinoma (BAC) is a subtype of adenocarcinoma, first reported by Malassez¹ in a 63-year-old woman whose multiple lung nodules had "l'aspect du fromage de Roquefort" (the appearance of Roquefort cheese). He also described the classic histology of neoplastic cells growing along the alveolar walls without invasion, preserving the general alveolar architecture. In 1960, BAC was further characterized by Liebow² by its well-differentiated cytology and its propensity for multicentric development. Reports of the incidence of BAC vary between 5 to 25% of all lung cancers, depending on disparities in the application of strict pathologic criteria. The 2004 World Health Organization (WHO) criteria restrict the definition of BAC to those tumors without any evidence of stromal, pleural, or lymphatic invasion. BAC differs from such benign alveolar proliferative conditions as atypical adenomatous hyperplasia by the fact that the latter usually includes multiple cell lines (ie, both ciliated and cuboidal epithelium).

Patients with BAC may present differently than those with other histologic subtypes of lung cancer. A review³ of more than 300,000 lung cancer patients identified from the Surveillance, Epidemiology and End Results (SEER) database found that patients with BAC were more likely to have local disease and better 1-year survival (65% vs 39% for non-BAC adenocarcinoma) than those with other lung cancers. Likewise, radiographic abnormalities may be clinically silent and exist for extended periods of time before diagnosis. In one review⁴ of 105 surgically treated patients with BAC, 12% had had a stable solitary nodule for 2 to 7 years before diagnosis. Therefore, the 7-year period through which the CT scan remained relatively stable in this index patient’s case, although lengthy, is not unusual.

Among patients with ground-glass opacities on chest CT scans, an extended period of observation may be required to distinguish benignity from malignancy.

References:

1. Malassez L. Examen histologique d'un cas de cancer encephaloide du poumon (epithelioma). Arch Physiol Norm Pathol 1876; 3:353-372
2. Liebow AA. Bronchiolo-alveolar carcinoma. Adv Intern Med 1960; 10:329-358
3. Read WL, Page NC, Tierney RM, et al. The epidemiology of bronchioloalveolar carcinoma over the past two decades: analysis of the SEER database. Lung Cancer 2004; 45:137-142
4. Dumont P, Gasser B, Rouge C, et al. Bronchoalveolar carcinoma: histopathologic study of evolution in a series of 105 surgically treated patients. Chest 1998; 113:391-395

Puzzler Case Report submitted by:
Marc B. Feinstein, MD, FCCP
Thoracic Oncology NetWork Steering Committee Member