[Leukemia cutis arising at the site of injection of a tetanus vaccine booster].

Leukemia cutis is a rare disorder. Although its prognostic usefulness is known—since it is frequently associated with a poorer prognosis for the underlying disease1—the mechanism that leads it to develop in a specific site is unknown. We describe a case of leukemia cutis which developed at the site of injection of a tetanus vaccine booster. The male patient, aged 64 years, was an exsmoker with a history of hyperuricemia. He had been diagnosed with chronic myelomonocytic leukemia in 2004 during a study of persistent monocytosis in circulating blood. He consulted 3 years later with a lesion that had developed at the injection site of a tetanus vaccine booster. Commencing as a small papule, the lesion progressively grew to become a violaceous mass, friable to the touch, measuring 7 cm by 5 cm (Figure 1). Observed over the following weeks and developing in parallel with the growth of the skin tumor, was a generalized bilateral and symmetric eruption, consisting of macules and papules in confluent plaques, brownishpurple in color, and most evident on the anterior aspect of the trunk (Figure 2). The histopathology study confirmed the presence of a dense infiltrate in the middle and deep dermis, composed of granulocytic cells at different stages of development and with frequent mitoses (Figures 3 and 4). An immunohistochemical study of the cells revealed them to be positive for CD68 and CD43. A predominantly periadnexal and perivascular infiltrate extended between the collagen fibers, but spared the Grenz zone and the epidermis. These findings enabled a diagnosis of skin infiltration by chronic myelomonocytic leukemia to be reached. A computed tomography scan revealed supradiaphragmatic and infradiaphragmatic lymphadenopathies and hepatosplenomegaly, with no changes with respect to previous scans. A bone marrow biopsy showed signs of infiltration by chronic myelomonocytic leukemia, but with no changes with respect to previous studies. In view of the diagnosis of leukemia cutis, intensive chemotherapy was commenced with idarubicin, cytarabine, and etoposide, complemented with radiotherapy for the largest tumor. The patient experienced a complication due to infection caused by extended-spectrum b-lactamaseproducing Klebsiel la pneumoniae and St aphylococcus haemolyt icus; this was considered to be secondary to the postchemotherapy aplasia. Response to antibiotic