Benign myoepithelioma of the lung - a case report and review of the literature

Abstract

Introduction: Benign myoepithelioma is extremely rare in the lung, to the best of our knowledge; only five cases have been reported in the literature.

Case report: An 18-years woman complained from tiredness and fever during four months. Laboratory findings and fibroscopies were normal. CT of the thorax demonstrated a nodule in the left segment of the Fowler. Left inferior lobectomy was performed comporting a firm nodule of 25 mm, lifting the bronchial mucous membrane. Histologically, there was a proliferation of small cells of a plasmocytoid-type, with a predominantly whorled pattern. No mitotic activity or necrosis was seen in the tumor. Immuhistochemically, the tumor cells positive for smooth muscle actin, vimentine, and S100 protein. They were negatives for cytokeratine, chromogranine and HMB45. The diagnosis of benign myoepithelioma of the lung is so confirmed. The patient recovered well at 6 months follow-up.

Conclusion: Benign myoepithelioma is a rare pulmonary neoplasm distinct from pleomorphic adenoma, which should be considered in the differential diagnosis of lung nodules.

Figure 1

Endobronchi tumor proliferation (HE ×40).

Figure 2

Small cells proliferation of plasmocytoid-type, in a whorled pattern. The nuclei showed dispersed chromatin with no mitotic activity (HE ×400).

Figure 3

Immunohistochemestry: Diffuse positivity for Actine smooth muscle.

Figure 4

Tumor cells positive to S100 protein.

Figure 5

Tumor cells negatives to cytokeratine.