Usefulness of Ki‐67 (MIB‐1) immunostaining in the diagnosis of pulmonary sclerosing hemangiomas

Pulmonary sclerosing hemangioma (PSH) is an uncommon lung neoplasm with a clinical outcome that is generally benign. However, differentiating PSH from pulmonary carcinoma is sometimes difficult as both lesions share similar histopathologic and immunohistochemical features. In this study, we investigated the usefulness of Ki‐67 (MIB‐1) immunostaining in the diagnosis of PSH. We compared the staining pattern for Ki‐67 (MIB‐1) in 29 cases of typical PSH and 79 cases of pulmonary non‐small cell carcinoma (NSCLC) using an immunohistochemical method on formalin‐fixed paraffin‐embedded tissues. In all studied PSH cases, we noted cell membrane and cytoplasmic staining for Ki‐67 (MIB‐1), but this was not observed in any of the NSCLC cases. The Ki‐67 proliferation index was lower in PSH than in the NSCLC cases (mean, 1.1% vs mean, 5.5%; p < 0.001). These findings suggest that cell membrane and cytoplasmic staining for Ki‐67 (MIB‐1), as well as the Ki‐67 proliferation index, may be useful for distinguishing PSH from pulmonary carcinoma.