The Diagnosis: Myeloid Leukemia Cutis
Leukemia cutis represents the infiltration of leukemic cells into the skin. It has been described in the setting of both myeloid and lymphoid leukemia. In the setting of acute myeloid leukemia, it has been reported to occur in 2% to 13% of patients overall,1,2 but it may occur in 31% of patients with the acute myelomonocytic or acute monocytic leukemia subtypes.3 Leukemia cutis is less common, with chronic myeloid leukemia occurring in 2.7% of patients in one study.4 In another study, 65% of patients with myeloid leukemia cutis had an acute myeloid leukemia.5
Myeloid leukemia cutis has been reported in patients aged 22 days to 90 years, with a median age of 62 years. There is a male predominance (1.4:1 ratio).5,6 The diagnosis of leukemia cutis is made concurrently with the diagnosis of leukemia in approximately 30% of cases, subsequent to the diagnosis of leukemia in approximately 60% of cases, and prior to the diagnosis of leukemia in approximately 10% of cases.5
Clinically, myeloid leukemia cutis presents as an asymptomatic solitary lesion in 23% of cases or as multiple lesions in 77% of cases. Lesions consist of pink to red to violaceous papules, nodules, and macules that are occasionally purpuric and involve any cutaneous surface.5
Histologically, the epidermis is unremarkable. Beneath a grenz zone within the dermis and usually extending into the subcutis there is a diffuse or nodular proliferation of neoplastic cells, often with perivascular and periadnexal accentuation and sometimes single filing of cells between collagen bundles (Figure 1). The cells are immature myeloid cells with irregular nuclear contours that may be indented or reniform (Figure 2). Nuclei contain finely dispersed chromatin with variably prominent nucleoli.5,6 Immunohistochemically, CD68 is positive in approximately 97% of cases, myeloperoxidase in 62%, and lysozyme in 85%. CD168, CD14, CD4, CD33, CD117, CD34, CD56, CD123, and CD303 are variably positive. CD3 and CD20, markers of lymphoid leukemia, are negative.5-8
Figure 1. Beneath a grenz zone, a diffuse proliferation of neoplastic cells with single filing of cells between collagen bundles (H&E, original magnification ×40).
Figure 2. Pleomorphic cells with variably indented nuclei were seen (H&E, original magnification ×400).
Leukemia cutis in the setting of a myeloid leukemia portends a grave prognosis. In a series of 18 patients, 16 had additional extramedullary leukemia, including meningeal leukemia in 6 patients.2 Most patients with myeloid leukemia cutis die within an average of 1 to 8 months of diagnosis.9