Blasts with folded nuclei: A histopathologic finding in myeloid leukemia cutis with NPM1 and FLT3 mutations.

Leukemia cutis is a term used to describe cutaneous manifestations of leukemic infiltration of the skin and portends a poor prognosis. Cutaneous involvement by hematopoietic/lymphoid tumors can occur before, concurrently, or after the initial diagnosis. Early involvement of dermatologists and timely biopsies play a crucial role in achieving a prompt diagnosis. Prior reports of acute myeloid leukemia have revealed a strong association between the cup-like nuclear morphology observed in bone marrow specimens and concurrent mutations of NPM1 and FLT3-ITD. In cutaneous tissue sections of leukemia cutis, folded or indented nuclei may represent the "cup-like" counterpart previously described in bone marrow specimens. Recognizing this morphological feature could aid in identifying this molecular subtype of leukemia cutis. In this study, we present a case of leukemia cutis in a 63-year-old female with AML and NPM1 and FLT3-ITD mutations, demonstrating scattered indented/folded nuclei.