SAN FRANCISCO (EGMN) - The diagnosis of blastic natural killer-cell lymphoma requires a dermatopathologist who knows the typical immunohistochemical patterns of the disease and who also is aware of exceptions to rules.Also called CD4-positive, CD56-positive (CD4+/CD56+) hematodermic neoplasm, the disease is a rare, aggressive malignancy that frequently presents with skin lesions. Subjecting punch biopsy specimens to a battery of immunohistochemical stains typically produces immunopositivity for CD4,...