LAUSR

BACKGROUND Primary malignant melanoma of the lung (PMML) is a rare and highly malignant tumor with a poor prognosis. Here, we report a PMML case diagnosed by computed tomography (CT)-guided percutaneous biopsy, describe its pathological features and review relevant literature to improve our understanding of this tumor. CASE SUMMARY A 64-year-old Chinese female presented with productive cough for 7 mo. A chest CT scan showed a large and space-occupying lesion in Lingual lobe. Positron emission tomography-CT revealed multiple nodules located in the superior lobe apicoposterior segment of her left lung. Brain magnetic resonance imaging showed numerous enhancing nodules, suggesting brain metastasis. Abdominal CT scan did not show any abnormalities. By CT-guided percutaneous biopsy, four pieces of gray and taupe tissues (1 cm length and 0.1 mm in diameter) were obtained. After pathologic examination, the tumor was found to consist of epidermal and nested small round cells, fibrosis and thin-walled blood vessels. The finding was suggestive of malignant melanoma. To confirm the diagnosis, pathological morphology and immunophenotypic features of the biopsy specimens were observed. The patient denied any history of skin tumors. No abnormal lesions were detected in other sites of the body. Molecular testing was positive for wild-type EGFR and KIT gene mutations. Finally, the clinical and pathological findings suggested PMML. CONCLUSION PMML is very rare, and the percutaneous biopsy tissue is limited. Therefore, comprehensive consideration of histology, immunohistochemistry, imaging, and clinical information is important for the diagnosis of PMML.