Children with hematologic malignancies may be challenged with life-threatening, invasive fungal infections by organisms that would otherwise have a low potential for virulence in healthy hosts. Presented is a case of a 15-year-old adolescent with B-cell acute lymphoblastic leukemia who was receiving steroids and chemotherapy. He developed cough associated with left chest pain with suspicion for fungal pneumonia. He began systemic antifungal therapy, underwent computed tomography of the chest demonstrating a large cavitary lesion (reversed halo sign) in the left lung. Over a 48-hour period the patient clinically deteriorated with worsening pneumonia and required left thoracotomy with nonanatomic pulmonary resection. This case illustrates the aggressive nature of Cunninghamella pneumonia in patients with hematologic malignancies, and the multidisciplinary approach required to have the greatest possible outcome.