CD30 Expression Is Rare in Myeloid Leukemia Cutis: A Study of 55 Cases and Implications for Routine Diagnostic Algorithms.

Expression of CD30 in blastoid cutaneous infiltrates typically signifies a CD30 lymphoproliferative disorder, often requiring minimal immunohistochemical workup, if clinically consonant. However, myeloid and other hematologic malignancies often express CD30. We retrospectively examined the prevalence of CD30 expression in 41 patients (median age 59) and 55 biopsies with the diagnosis of leukemia cutis (LC) to determine whether an extensive immunohistochemical workup is warranted in all large, round cell CD30 cutaneous infiltrates. Each patient had refractory or recurrent disease, the histologic presence of a large mononuclear cell infiltrate, and varied cytogenetics. CD30 mononuclear cells within the infiltrate ranged from rare to many in 22 biopsies (22/55). In 18 biopsies, CD30 cells were interpreted as lymphocytic based on morphology, strong cytoplasmic and Golgi staining for CD30, and negative CD34 and CD117 staining. One case showing 3+ staining of lymphocytes was identified as a posttransplant lymphoproliferative disorder. The second 3+ case was favored to represent a subset of CD30-positive acute myeloid leukemia. Three other cases with 1+ membranous and cytoplasmic staining were interpreted as myeloid leukemia. In conclusion, CD30 positivity in myeloid leukemia in the skin is rare and does not often exhibit the strong membranous (2+ or 3+) and/or Golgi staining seen in reactive lymphocytes. Acute myeloid leukemia or myeloid LC may occasionally show 1+ (and rarely 2-3+) cytoplasmic/membranous or nonspecific blush nuclear CD30 labeling. Strong diffuse staining for CD30 should prompt consideration of a reactive lymphoid/lymphoproliferative process, and, when the clinical likelihood of CD30 LC is low, may obviate the need for further immunohistochemistry.