Background <p>Leukemia cutis (LC) is an extramedullary manifestation of leukemia that occurs when neoplastic cells infiltrate the epidermis, dermis, or subcutaneous tissue of the skin. The clinical presentation of LC can vary significantly and is typically a late sign in advanced disease. In this case report, we describe a diagnostically challenging case of LC in a 10-year-old girl who initially presented with a solitary morphea-like plaque on her scalp, which ultimately led to the diagnosis of B-cell acute lymphoblastic leukemia (B-cell ALL).</p> Case presentation <p>We present a challenging case of a 10-year-old female who initially presented with a scarring alopecic, morphea-like plaque on the right parietal scalp. Over two months, the lesion proved unresponsive to high-dose topical corticosteroid therapy and demonstrated progressive enlargement. The clinical course was further complicated by the emergence of systemic symptoms, including recurrent fever and significant cervical lymphadenopathy, which prompted referral for further evaluation. A definitive diagnosis of B-cell ALL was established based on congruent histopathological and immunohistochemical profiles from biopsies of the scalp lesion and cervical lymph nodes, which were confirmed by bone marrow examination. The patient achieved complete remission of the cutaneous lesion and systemic disease following one month of chemotherapy according to the Berlin-Frankfurt-Münster (BFM) protocol.</p> Conclusion <p>Given the highly variable clinical presentations of leukemia cutis, this case highlights the critical necessity of including it in the differential diagnosis of atypical sclerotic scalp lesions in children. A strong clinical suspicion is required for the timely diagnosis of uncommon cutaneous presentations of underlying hematologic malignancy. Appropriate biopsy and the prompt initiation of systemic chemotherapy are paramount for achieving favorable outcomes and remission.</p>