Sean Klepper M.D.
Artur Zembowicz M.D....
- Cutaneous involvement by systemic leukemia is a poor prognostic sign, often associated with an impending blast crisis.
- It is rarely the initial manifestation of the disease.
- Cutaneous involvement is most common in acute myelogenous leukemia (AML), in which monocytic and myelomonocytic leukemia are especially prone to involve the skin, and much more rare in acute lymphoblastic leukeumia (ALL) and chronic myeloid leukemia (CML).
- Any part of the skin may be involved. Presentations are variable, most commonly violaceous papules and nodules.
- Histologic confirmation is required in cases of suspected leukemia cutis, as patients with leukemia can develop a variety of other skin pathology, including ecchymoses, drug reactions, opportunistic infections, GVHD, leukocytoclastic vasculitis, pyoderma gangrenosum and Sweet's syndrome.
- The degree of dermal infiltration varies from small perivascular deposits to diffuse dermal involvement.
- Involvement of the epidermis and adnexae is variably present.
- Cytologic features depend on the type of leukemia present:
- AML shows blasts with dispersed chromatin, often prominent nucleoli and high N:C ratios
- Monocytic leukemia (AML type M5) and myelomonocytic leukemia (AML type M4) typically show folded or reniform nuclei.
- ALL often shows medium large blasts with vesicular nuclei, which may extend into the subcutaneous fat.
- The infiltrates in CML are composed of mature neutrophils and neutrophilic precursors.
- As with the morphology, the immunophenotype varies with the type of leukemia involved. Imuunophenotypic classification of leukemias is beyond the scope of this book.