Radiolucencies and cavitation in bronchioloalveolar carcinoma: CT-pathologic correlation

Bronchioloalveolar carcinoma (BAC) is a polymorphic lung cancer the incidence of which is rising. The presence of intratumoral radiolucencies is an important feature of bronchioloalveolar carcinoma. The aim of this study was to present pictorially the spectrum of intratumoral radiolucencies visible in BAC. In 57 BACs studied with thin-slice CT, we identified six types of radiolucencies: (a) patent intratumoral bronchioles (air bronchiologram); (b) pseudocavitations; (c) cavitation; (d) serpentine radiolucencies; (e) internal alveologram; and (f) multiple cystic lesions.

[Contrast-enhanced study of solitary pulmonary nodules with thin-section computed tomography]

INTRODUCTION

Since many benign and malignant pathologic conditions can appear as solitary pulmonary nodules, to establish nodule nature is always necessary for correct patient management. Recently, some authors have demonstrated the effectiveness of incremental dynamic CT in distinguishing cancerous from noncancerous lesions. The purpose of this work is to report our personal experience in this field.

MATERIAL AND METHODS

We reviewed the incremental dynamic CT scans of 21 patients with a solitary pulmonary nodule < 3.5 cm phi without any calcifications, cavities and fat--namely, 15 carcinomas, 3 granulomas, 2 hamartomas, 1 abscess. Lesion density was evaluated before and 30 s, 1, 2, 3 and 5 min after contrast agent administration; we used a circular region of interest consisting of the central portion of the nodule in all cases and of 60-70% of its area in most cases. We subdivided the nodules into two groups, according to their enhancement: the nodules with > 20 HU and those with < 20 HU. All the lesions were submitted to surgery and histologic studies.

RESULTS

Fourteen of 15 carcinomas and one hamartoma had contrast enhancement > 20 HU; an abscess exhibited marked ring-shaped contrast enhancement (positive predictive value: 87%). One carcinoma, three granulomas and one hamartoma had no contrast enhancement, or else it was < 20 HU (negative predictive value: 80%).

DISCUSSION

Recently, some authors have demonstrated that malignant nodules, studied with incremental dynamic CT, have higher contrast enhancement than benign nodules. A value > 20 HU is a good predictor of malignancy (positive predictive value: 90%) and, conversely, a value < 20 HU is an unquestionable sign of benignity (negative predictive value: 100%). Our findings confirm the positive predictive value of enhancement > 20 HU, but not its negative predictive value because we found a malignant nodule without contrast enhancement.

CONCLUSIONS

Incremental dynamic CT is an effective indicator of solitary pulmonary nodule nature, but its predictive value is not absolute and therefore this technique should be integrated with biopsy in the cases which are clinically or radiologically suspicious.

CT-pathologic correlation in nodular bronchioloalveolar carcinoma

OBJECTIVE

We retrospectively reviewed CT and pathologic examinations in resected nodular bronchioloalveolar carcinomas (BACs) to correlate the histology with the appearance of the nodules on preoperative thin section CT images.

MATERIALS AND METHODS

Thin section CT scans of 11 patients with nodular BAC were reviewed by two observers. In each case, size, tumor-lung interface, and internal characteristics of the nodule were recorded and correlated with histopathologic examinations.

RESULTS

Computed tomography showed a large bronchus leading to or contained within the nodule in 36%; spiculated, lobulated, or irregular borders in 82%; pleural retraction in 36%; internal inhomogeneity in 45%; and a zone of intermediate attenuation surrounding a higher attenuation nodule and separating it from the surrounding lung parenchyma (the CT halo sign) in 18% of the 11 BACs. In two lesions internal serpentine radiolucencies could be seen. Histopathologic studies showed this correlated with the air-containing glandular spaces of the tumor.

CONCLUSION

The CT halo sign and serpentine radiolucencies should be added to the list of the CT findings of nodular BAC. However histologic examination is required to confirm the diagnosis of BAC.

Bronchus sign on CT in peripheral carcinoma of the lung: value in predicting results of transbronchial biopsy

The bronchus sign on CT represents the presence of a bronchus leading directly to a peripheral pulmonary lesion. We investigated the value of this sign in predicting the results of transbronchial biopsy and brushing in 33 consecutive cases of proved peripheral bronchogenic carcinoma studied with thin-slice CT (2-mm-thick sections). The bronchus sign was seen on CT in 22 patients and was absent in 11. Transbronchial biopsy and brushing showed peripheral carcinoma in 13 (59%) of 22 patients in whom the bronchus sign was seen on CT and in only two (18%) of 11 patients in whom it was not seen. The difference is statistically significant (Fisher's exact test, p = .029). When analyzed by the order of involved bronchus, a 90% success rate of transbronchial biopsy and brushing was found in patients in whom the bronchus sign was seen at a fourth-order bronchus (p = .01). This compared with a success of 33% when the bronchus sign was seen at fifth-, sixth-, or seventh-order branches. Our results suggest that the bronchus sign at a fourth-order bronchus is valuable in predicting the success of transbronchial biopsy and brushing. The presence of the sign on CT may be useful in determining if the workup should include transbronchial biopsy and brushing or transthoracic needle aspiration in patients with peripheral lung lesions.

[The enhancement phenomenon of serous cavity effusions]

The enhancement of ascites following a high dose of contrast medium has been recently described. The CT behavior of 26 peritoneal, pleural or pericardial effusions has been studied in 23 patients after the administration of a high dose of urographic contrast medium. The effusions were enhanced in all patients but one. No difference between malignant and non-malignant effusions could be observed with ionic and non-ionic contrast medium. Low molecular weight of the urographic contrast medium (600-800 daltons) can explain the free passage of the solute through peritoneum, pleura, and pericardium. The knowledge of such a phenomenon is mandatory to avoid misdiagnosing hematic effusion or urinary-peritoneal fistula.

[Bronchogenic carcinoma with extramucosal development. Diagnostic problems]

Bronchogenic carcinoma is characterized by three different patterns of spread: endobronchial, the commonest, submucosal, and peribronchial. While the diagnostic yield of bronchoscopy is very high for endobronchial masses, both submucosal and peribronchial tumors are more difficult to detect, and standard forceps biopsy can be negative. In such cases transbronchial needle aspiration biopsy allows higher diagnostic accuracy. CT findings of extramucosal neoplastic spread are not specific. Thickening of the bronchial walls is the commonest sign, but CT is inaccurate in predicting whether bronchial thickening will result in endobronchial/extramucosal neoplasm, fibrosis or bronchial wall edema. Despite this inaccuracy, CT is complementary to bronchoscopy since it allows to: 1) detect a pathology in the bronchial walls, which appear thickened; 2) delineate the extent of extraluminal spread; 3) help plan transbronchial needle aspiration biopsy.