Bronchioloalveolar carcinoma and adenocarcinoma with bronchioloalveolar features presenting as ground-glass opacities on CT.

Objective: As bronchioloalveolar carcinoma (BAC) is noninvasive but, in its later stages, has a worse prognosis than adenocarcinoma with bronchioloalveolar features (ACB), early identification and differentiation is important for therapeutic and prognostic purposes. We wanted to identify features of BAC, which differentiated it from ACB when both presented as ground-glass opacities (GGOs) on CT.

Materials And Methods: We reviewed all pathologic specimens of patients who were diagnosed with BAC and ACB in the lung from 1991 to 1999 in our institution and whose malignancy presented as a GGO on CT. This yielded 29 patients, 15 with BAC and 14 with ACB with GGOs on CT. Both univariate frequency table and multivariate logistic regression approaches were used to analyze the CT characteristics of these GGOs (location, GGO pattern, size, shape, margin, presence and type of air bronchogram and pseudocavitation).

Results: BAC most frequently had a "GGO halo" around a solid opacity, often was a GGO "mixed with consolidation" with the smallest BACs being "pure GGO." Air bronchograms were frequently present in the largest GGOs. Pseudocavitations were rare. ACB, on the other hand, most frequently presented as a GGO "mixed with consolidation," less frequently with a "GGO halo" and rarely with "superimposed lymphangitis." The air bronchograms, frequently present, were usually tortuous and ectatic. Pseudocavitation was present in about one-third of the cases. The most useful CT features of GGO in separating those due to BAC from those due to ACB were pure (uniform) ground-glass attenuation and absence of lymphangitis.

Conclusion: The CT features of BAC and ACB presenting as GGO reflect the histologic descriptions of these carcinomas.