A tale of two clones: Caldesmon staining in the differentiation of cutaneous spindle cell neoplasms.

The Ventana caldesmon clone is not specific to smooth muscle, a potential pitfall to laboratories using this clone. The staining pattern, sensitivity and specificity of the Dako H-caldesmon antibody clone are similar to results from prior studies. The sensitivity and specificity of the Dako clone support its use in smooth muscle identification as an additional marker in challenging cases.