A rare radiological presentation of pulmonary metastases from malignant melanoma

Abstract

Malignant melanoma is a highly aggressive cancer with metastatic potential to various locations such as the lymph nodes, lungs, liver, brain, and bone. After the lymph nodes, the lungs are the most common site of malignant melanoma metastases. Pulmonary metastases from malignant melanoma commonly presents as solitary or multiple solid nodules, sub-solid nodules or miliary opacities on CT chest. We present a case of pulmonary metastases from malignant melanoma in a 74-year-old man which presented unusually on CT chest as a combination of patterns like "crazy paving," upper lobe predominance with subpleural sparing, and centrilobular micronodules. Video-assisted thoracoscopic surgery, wedge resection and tissue analysis were performed, which confirmed the diagnosis of malignant melanoma metastases, and the patient further underwent PET-CT for staging and surveillance. Patients with pulmonary metastases from malignant melanoma can have atypical imaging findings, therefore radiologists should be aware of these unconventional presentations to avoid any misdiagnoses.

Keywords: Atypical presentation; Crazy paving; Malignant melanoma; Oncology; Pulmonary metastases.

Fig. 1

Axial CT chest image lung window (A) demonstrates bilateral diffuse consolidation and ground glass opacities with superimposed septal thickening, giving a “crazy-paving” pattern (red arrows). There is relative subpleural sparing. Coronal reformatted lung window (B) shows airspace disease predominantly involving upper lobes of lungs (yellow arrows) with relative sparing of bilateral lower lobes (black arrows).

Fig. 2

Axial CT chest image lung window performed 4 weeks after baseline CT demonstrates interval worsening of bilateral diffuse airspace disease with crazy-paving pattern (red arrows).

Fig. 3

Postoperative chest radiograph after wedge resections of right lung demonstrates bilateral diffuse airspace disease with expected postsurgical right subcutaneous emphysema (black arrow) and trace right pneumothorax. Right chest drainage tube is noted in the lung base (red arrow).

Fig. 4

Representative H&E-stained slides showing the tumor histology. (A) The low-power picture shows diffuse growth of tumor containing dark-brown pigmentation. (B) At higher power magnification, the tumor cells show malignant nuclear features with melanin production (black arrows), consistent with metastatic melanoma.

Fig. 5

FDG PET-CT axial section at the level of lungs (A) demonstrates avid uptake of FDG in bilateral diffuse airspace disease, consistent with pathology proven metastatic melanoma. FDG PET-CT axial section at the level of liver (B) demonstrates multiple avid FDG uptake involving both lobes of the liver, posterior chest wall and peritoneum, favoring metastatic disease. FDG PET image (C) demonstrates extensive FDG avid metastatic disease involving whole body.

Fig. 6

Axial section post contrast T1 weighted images (A and B) demonstrates enhancing intraparenchymal lesions concerning for metastases in the ventral pontomedullary junction of the brainstem (red arrow in Fig. A) and in the right cerebral cortex (red arrow in Fig. B).