Tumor size and computed tomography attenuation of pulmonary pure ground-glass nodules are useful for predicting pathological invasiveness.

OBJECTIVES: Pulmonary ground-glass nodules (GGNs) are occasionally diagnosed as invasive adenocarcinomas. This study aimed to evaluate the clinicopathological features of patients with pulmonary GGNs to identify factors predictive of pathological invasion. METHODS: We retrospectively evaluated 101 pulmonary GGNs resected between July 2006 and November 2013 and pathologically classified them as adenocarcinoma in situ (AIS; n = 47), minimally invasive adenocarcinoma (MIA; n = 30), or invasive adenocarcinoma (I-ADC; n = 24). The age, sex, smoking history, tumor size, and computed tomography (CT) attenuation of the 3 groups were compared. Receiver operating characteristic (ROC) curve analyses were performed to identify factors that could predict the presence of pathologically invasive adenocarcinomas. RESULTS: Tumor size was significantly larger in the MIA and I-ADC groups than in the AIS group. CT attenuation was significantly greater in the I-ADC group than in the AIS and MIA groups. In ROC curve analyses, the sensitivity and specificity of tumor size (cutoff, 11 mm) were 95.8% and 46.8%, respectively, and those for CT attenuation (cutoff, -680 HU) were 95.8% and 35.1%, respectively; the areas under the curve (AUC) were 0.75 and 0.77, respectively. A combination of tumor size and CT attenuation (cutoffs of 11 mm and -680 HU for tumor size and CT attenuation, respectively) yielded in a sensitivity and specificity of 91.7% and 71.4%, respectively, with an AUC of 0.82. CONCLUSIONS: Tumor size and CT attenuation were predictive factors of pathological invasiveness for pulmonary GGNs. Use of a combination of tumor size and CT attenuation facilitated more accurate prediction of invasive adenocarcinoma than the use of these factors independently

Patient characteristics and tumor properties.

<p>Abbreviations: AIS, adenocarcinoma in situ; MIA, minimally invasive adenocarcinoma; I-ADC, invasive adenocarcinoma; CEA, carcinoembryonic antigen; CT, computed tomography; HU, Hounsfield unit.</p>#<p>significantly higher than tumor size in the AIS group.</p><p>*significantly higher than CT attenuation in the AIS and MIA groups.</p

Representative radiological and histological images.

<p>(a) A 64-year-old female patient with adenocarcinoma <i>in situ</i>. (i) Computed tomography (CT) scan (lung window setting) showed a pure ground-glass nodule (GGN), 11.9 mm in size. The mean CT attenuation of the tumor was −716 Hounsfield units (HU). (ii) Mediastinal window setting CT showed no tumor components except for vessels. (iii) Low magnification image (hematoxylin and eosin (HE) staining) showed a circumscribed tumor growing purely with a lepidic pattern without foci of invasion. A slight thickening of the alveolar walls in the tumor area was observed. (iv) Middle magnification image of the tumor (HE staining) revealed that tumor cells appeared to replace normal pneumocytes on alveolar walls. (b) A 63-year-old female patient with minimally invasive adenocarcinoma. (i) Lung window CT image showed a pure GGN, 14.2 mm in size. The mean CT attenuation was −691 HU. (ii) Mediastinal window CT showed no tumor components. (iii) Low magnification image of the tumor (HE staining) revealed a subpleural tumor consisting predominantly of lepidic growth with a small (<5 mm) focus of invasion. (iv) Middle magnification image of the invasive area of the tumor (HE staining) revealed acinar-type growth pattern. (c) A 74-year-old female patient with lepidic-predominant invasive adenocarcinoma. (i) Lung window CT showed a pure GGN, 19.7 mm in size. The mean CT attenuation was −618 HU. (ii) Mediastinal window CT showed no tumor components except for vessels. (iii) Low magnification image (HE staining) revealed a tumor consisting mostly of lepidic growth with a smaller area (8 mm) of acinar invasion. (iv) Middle magnification image of the invasion area of the tumor (HE staining) revealed acinar gland proliferation in the fibrous stroma. (d) A 76-year-old male patient with papillary-predominant invasive adenocarcinoma. (i) Lung window CT image showed a pure GGN, 10.7 mm in size. The mean CT attenuation was −509 HU. (ii) Mediastinal window CT showed no tumor components. (iii) Low magnification image of the tumor (HE staining) revealed that the tumor predominantly consisted of papillary proliferation. (iv) Middle magnification image of the tumor (HE staining) revealed cuboidal tumor cells growing along fibrovascular cores in a papillary configuration.</p