Endobronchial spread in pulmonary adenocarcinoma

Clinical History

A patient with history of asthma presented with general malaise and worsening of wheezing during the night in the former 2 months. Chest radiography was initially ordered, with CT being ordered on follow-up.

Imaging Findings

Figure 1: Chest radiography (front and profile): opacity in the upper lobe of the right lung, apparently respecting the fissure.
Figure 2: CT six weeks after (lung window, sagittal and coronal reformat) - persistent consolidation with slight air bronchogram, and apparent transfissural spread.
Figure 3: Axial CT (lung and soft tissue window), post e.v. contrast. Multiple well-defined nodes (circle) in the same lobe. Consolidation shows homogeneous enhancement and tapered air bronchogram (arrow).

Discussion

Adenocarcinoma is the most common histologic type of lung cancer, and may present with different types of macroscopic presentation, including pneumonia-like consolidation, especially in invasive mucinous adenocarcinoma (formerly mucinous bronchioloalveolar carcinoma). [1]

Air-space consolidation is represented in imaging by homogeneous opacity obscuring vessels, with air bronchogram, preserved lung volume, and fissures.

Classical differential diagnosis for this pattern of long pathology consist of the classical four substances [2]:
-Water (e.g. oedema)
-Blood (e.g. pulmonary haemorrhage)
-Pus (e.g. pneumonia)
-Cells (e.g. adenocarcinoma in-situ, organising pneumonia, etc).

Temporal persistence of lung consolidation despite therapy should prompt suspicion for oncologic pathology.

Despite adenocarcinoma in-situ being the most commonly recalled sub-type of cancer with this presentation, papillary sub-types may also present in such fashion. In some series, this latter type is the most common lung cancer presenting with consolidation. [2, 3]

Multiple lung nodules were the other significant finding. Differential diagnosis of multiple lung nodules includes metastasis almost universally, and in this case further suspicion should be added by the well-defined contours seen.

The most commonly acknowledged cancer spread pathways are lymphatic, haematogenous, local direct invasion and through the serosal cavities (pleural). In this case, ipsilateral and the same lobe distribution of nodules suggest aerogenous dissemination, which is also a possible cancer spread pathway particularly described for adenocarcinoma. Aerogenous dissemination is also thought to account for possible multricenticity of adenocarcinoma in-situ of the lung. [4]
In this case, bronchioloalveolar lavage was performed with fluid being processed in cell-block technique and imunnohistochemistry having been performed. Final diagnosis was consistent with adenocarcinoma of the micropapillary subtype, with imunohistochemistry indicating primary lung origin.
Micropapillary predominant adenocarcinoma has tumour cells growing in papillary tufts, which lack fibrovascular cores. [1] This type of tumour has a reported poor prognosis. [1]
The authors believe that this type of lung cancer architecture, with lack of a fibrovascular core, may be associated with aerogenous metastisation.

Important learning points for this case are to consider the possibility of malignancy for persistent lobar changes. In the event of an endobronchial spread pattern being detected, neoplastic disease should not be immediatly discarded, as this has been described as a potentially underrecognised form of lung cancer spread [4, 5].

Differential Diagnosis List

Final Diagnosis

Pulmonary adenocarcinoma (papillary subtype), with likely aerogenous metastasis

URL:	https://www.eurorad.org/case/15157
DOI:	10.1594/EURORAD/CASE.15157
ISSN:	1563-4086