Aleukemic Myeloid Leukemia Cutis with a Kikuchi Disease-Like Inflammatory Pattern in Myelodysplastic Syndrome

Myeloid leukemia cutis (MLC) is a rare disease characterized by the infiltration of neoplastic myeloid, myelomonocytic, or monocytic precursors into the skin, producing clinically nonspecific-appearing papules, nodules, plaques, or purpura that necessitate biopsy for definitive diagnosis. In general, it is considered an extramedullary manifestation of acute myeloid leukemia (AML) similar to myeloid sarcoma, also known as a chloroma. MLC often develops in patients with an established diagnosis of AML and is only rarely seen before the onset of systemic disease. Even more rarely, some patients are found to have an underlying nonleukemic bone marrow disease, such as a myelodysplastic syndrome (MDS). It is in these latter settings that the somewhat perplexing terminology aleukemic leukemia cutis (ALC) has been used widely. As may be imagined, establishing a diagnosis of ALC can be problematic and typically requires a high index of suspicion with careful integration of clinical, histopathological, and laboratory data. Once a diagnosis of ALC is made, a complete hematologic workup, including assessment of the patient's bone marrow, is essential because a diagnosis of MLC (with or without systemic leukemia) generally indicates a poor prognosis. When discovered in a patient with MDS, MLC has been suggested to herald progression toward more advanced disease. We present a rare case of so-called aleukemic myeloid leukemia cutis in an 82-year-old man subsequently diagnosed as having MDS without progression to overt AML. This case also illustrates a seemingly rare Kikuchi disease-like inflammatory pattern that obscured the underlying leukemic infiltrate in the skin, delaying its recognition.