DICER1 and pleuropulmonary blastoma: Immunohistochemical analysis for DICER1 protein expression in various tumors from patients known to harbor germline DICER1 mutations has yielded inconsistent results for both biological and technical reasons.4, 5 In PPB cases, for example, expression from the wild-type DICER1 allele has been shown to be lost in tumor epithelium, but is retained in the malignant mesenchymal cells,4 and differences in the sensitivity and specificity of individual DICER1 antibodies remain to be fully characterized.5