Pulmonary metastases from malignant melanoma showing ground-glass opacity nodules

To investigate the frequency and characteristics of pulmonary metastases from malignant melanoma presenting as ground-glass opacity nodules (GGNs) on chest computed tomography (CT).

A total of 354 patients with malignant melanoma who underwent chest CT for staging or follow-up were selected. We reviewed the CT images and enrolled 87 patients with lung metastases. Two radiologists evaluated the nodularity of the lung metastases (solid nodules or GGNs). Additionally, the tumor doubling time and disease type (mucosal, cutaneous, or acral melanomas) were analyzed.

GGNs were observed in 13 of 87 (14.9%) patients. The tumor doubling time was 52.0 ± 33.5 days (range: 10.9-111 days) for GGNs and 43.8 ± 27.5 days (range: 9.4-115.3 days) for solid nodules. GGNs changed to solid nodules in 54.5% of patients with increased GGN metastasis. More patients in the GGN group (patients whose metastases included GGNs) had mucosal melanomas than acral melanomas (p = 0.0478); however, no significant difference was observed in the frequency of mucosal and cutaneous melanomas (p = 0.0670). Similarly, the proportion of patients in the GGN-dominant pattern group (patients with GGNs only or more GGNs than solid nodules) who had mucosal melanomas was more than that of patients with acral and cutaneous melanomas (mucosal melanoma vs. acral melanoma, p = 0.0342; mucosal melanoma vs. cutaneous melanoma, p = 0.0344).

Lung metastases from malignant melanoma sometimes appear as GGNs on CT, with a frequency of 14.9% in this study. If lung metastasis is observed as a GGN, the tumor doubling time may be useful for differentiating lung metastasis of malignant melanoma from lung adenocarcinoma.