Lung Cancer Cavities Enlarged as Solid Components Regressed in Case Report

In a man in his 70s with metastatic invasive mucinous adenocarcinoma of the lung, computed tomography showed a difficult-to-interpret pattern during treatment: multiple pulmonary lesions developed or enlarged cavities while their residual solid components regressed. The cavities later continued to enlarge even as their walls became progressively thinner. Because the external dimensions of the lesions increased despite changes within them, the imaging findings did not provide an unambiguous assessment of pulmonary treatment response. This single-patient case report highlights a limitation of judging response primarily from the overall diameter of lesions that undergo marked cavitary transformation.

The man was referred to the hospital with multiple pulmonary nodules. His smoking history amounted to approximately 10 cigarettes per day for about 10 years during his twenties and thirties. Histopathological examination showed papillary and lepidic proliferation of mucin-producing tumor cells. At higher magnification, the tumor contained mucin-producing columnar cells with abundant intracellular mucin, consistent with invasive mucinous adenocarcinoma. The disease was staged as cT4N1M1b, or stage IVA. Molecular testing detected no actionable driver alterations, while programmed death-ligand 1 expression was measured at 15%. For a metastasis in the fourth thoracic vertebra, the patient received palliative radiotherapy at a dose of 35 Gy in five fractions.

Systemic treatment with atezolizumab, bevacizumab, carboplatin and paclitaxel was then initiated. On follow-up CT after two cycles, the solid components of the pulmonary tumors had regressed, but their cavitary components had enlarged. The overall dimensions of the lesions therefore increased even though the visible solid material had decreased. The investigators could not determine whether the tumors had progressed from the images alone, so another CT was obtained after two additional treatment cycles. That examination showed no significant changes in the lung fields, but the metastasis in the fourth thoracic vertebra had progressed. The overall disease was consequently judged to be progressive, and the systemic regimen was changed to docetaxel plus ramucirumab.

After three cycles of docetaxel plus ramucirumab, CT showed further enlargement of multiple cavitary lesions. At the same time, their walls became progressively thinner and the residual solid components appeared to regress. The findings were discordant in appearance: enlargement of the cavities could be interpreted as growth, whereas wall thinning and regression of the solid components were compatible with a treatment effect. The investigators concluded that these observations raised the possibility of treatment benefit but did not provide enough objective evidence to determine the overall pulmonary response. One additional chemotherapy cycle was administered, after which treatment was discontinued because the patient’s activities of daily living declined. He received no further chemotherapy and died approximately four months after the final cycle.

Cavitary lesions are commonly observed in squamous cell carcinoma but are relatively uncommon in adenocarcinoma. Cavitary change may also occur as a treatment-related radiological finding. The case report identifies several proposed mechanisms: central tumor necrosis, ischemia, communication with the bronchial tree, a treatment-related reduction in viable tumor cells, and changes in tumor blood flow induced by antiangiogenic agents. In this patient, marked cavitary transformation appeared during treatment with atezolizumab, bevacizumab, carboplatin and paclitaxel and progressed further during docetaxel plus ramucirumab. The investigators considered antiangiogenic therapy a possible contributor, while stating that the precise mechanism remained uncertain.

Inhibition of the vascular endothelial growth factor pathway may cause vascular regression, intratumoral ischemia and necrosis, processes that have been proposed to promote cavitary transformation during antiangiogenic treatment of non-small-cell lung cancer. The treatment sequence and imaging pattern in this case were temporally compatible with such a contribution because marked cavitation developed during the regimen containing bevacizumab and continued during a subsequent regimen containing ramucirumab. Nevertheless, the case cannot separate the effects of the two antiangiogenic agents from those of chemotherapy or immunotherapy, and it does not establish that either drug caused the imaging changes. It also cannot determine whether all enlarging cavities represented the same biological process.

The timing of cavitary transformation could not be established with certainty. A limited-field CT scan obtained two days before the first systemic regimen showed no cavitary changes in the portion of the lung included. That examination was performed primarily to evaluate the fourth thoracic vertebral metastasis and did not cover the entire lungs, so interval changes in lesions outside the imaged field could not be completely excluded. The absence of visible cavitation on the limited scan therefore did not definitively establish when it began. The later imaging nevertheless documented a clear sequence of enlarging cavities, thinning cavity walls and regressing residual solid components, producing the central radiological dilemma in this case.

Response assessment for solid malignancies commonly uses the Response Evaluation Criteria in Solid Tumors, or RECIST. The authors describe RECIST as a practical and useful standard for most patients, but the case demonstrates the difficulty posed by pronounced cavitary transformation. In this setting, an increase in external lesion diameter may suggest progression even when the residual solid component is regressing and the cavity wall is thinning. Overall diameter describes the lesion’s footprint, whereas the solid component and wall thickness describe features of its internal composition. When these measurements change in opposite directions, assessment based only on external size may become uncertain or potentially misleading.

Serum carcinoembryonic antigen, or CEA, and SLX levels did not resolve the uncertainty. Both remained within their normal ranges throughout treatment and therefore did not provide useful information for monitoring the response. The investigators concluded that marked, multifocal cavitary transformation can produce discordant morphological changes that complicate radiological evaluation. They state that assessment in such cases should incorporate cavity-wall thickness, residual solid components, overall tumor distribution and the clinical course rather than relying solely on external lesion diameter. These observations remain limited to one patient and cannot establish the frequency of the pattern, identify its biological cause or show that any particular regimen improved survival.

The case ultimately also demonstrates the limits of assigning a response when imaging, blood markers and the course at another metastatic site do not converge. Lung imaging suggested a possible treatment effect in the composition of the lesions, while progression in the fourth thoracic vertebra supported classifying the overall disease as progressive. No further systemic therapy followed, and the patient died roughly four months after the final chemotherapy cycle; those events do not establish what the pulmonary lesions represented or whether continued treatment would have changed the outcome. The report’s principal value is therefore focused and descriptive: it documents an uncommon imaging scenario in which enlarging cavities, thinning walls and regressing solid components coexist, making conventional size-based response assessment difficult and leaving clinicians to act amid persistent uncertainty.

Subject of Research: Treatment-related cavitary transformation complicating response assessment in invasive mucinous lung adenocarcinoma

Article Title: Discordant Cavitary Changes: A Radiological Dilemma in Invasive Mucinous Adenocarcinoma: A Case Report

Article References: Nigi, A., Miya, N., Iwamoto, K., Itani, H., & Kondou, S. (2026). Discordant Cavitary Changes: A Radiological Dilemma in Invasive Mucinous Adenocarcinoma: A Case Report. Respirology Case Reports, 14(10), Article e70791. https://doi.org/10.1002/rcr2.70791

Image Credits: AI Generated

DOI: 10.1002/rcr2.70791

Keywords: invasive mucinous adenocarcinoma, lung cancer, tumor cavitation, computed tomography, RECIST, antiangiogenic therapy, radiological response assessment, case report, bevacizumab, ramucirumab, Discordant, Cavitary