Leukemia Cutis Exhibiting the Koebner Phenomenon: A Rare Clinical Presentation of Acute Myeloid Leukemia.

Leukemia cutis with predilection for sites of prior cutaneous trauma, often described as a Koebner-like phenomenon, is a rare but recognized occurrence. We present a unique case of an, otherwise, healthy male who developed leukemia cutis at a prior unrelated biopsy site, leading to a new diagnosis of acute myeloid leukemia (AML). Certain AML subtypes with extramedullary propensity, particularly M4 and M5, as seen in our patient, are associated with an increased risk of leukemia cutis. Unlike their medullary counterparts, extramedullary AML cells preferentially migrate to and persist in tissues outside the bone marrow, where the local microenvironment may promote immune escape. Although the localization of leukemia cutis to the biopsy site is consistent with a Koebner-like response, it remains uncertain whether subclinical leukemic cells were already present at the time of the initial excision; therefore, a definitive causal relationship between trauma and leukemic infiltration cannot be established. Additionally, the prior keratoacanthoma and its excision may have created a localized immunocompromised cutaneous district, or locus minoris resistentiae, further predisposing the site to leukemic cell infiltration. The immunologic features of extramedullary AML, including impaired antigen presentation and T-cell exhaustion, overlap with this concept of localized immune dysregulation and may have facilitated site-specific leukemic infiltration. New infiltrative plaques at sites of prior skin trauma or biopsy warrant prompt biopsy and histopathological evaluation, even in patients without known hematologic malignancy. Leukemia cutis may represent the first manifestation of underlying acute leukemia, making early recognition critical for timely oncologic referral and treatment.