Chronic neutropenia is a rare but important challenge with substantial clinical implications for patients receiving antineoplastic treatment. Treatment-induced neutropenia is a well-known adverse event during chemotherapy and some targeted treatments. Guidelines for administering chemotherapy are rather strict to protect the patient from severe and life-threatening complications. Consequently, patients with chronic neutropenia may receive suboptimal antineoplastic treatment. Autoimmune neutropenia or chronic idiopathic neutropenia (CIN) may affect the antineoplastic treatment by causing delayed drug delivery, dose reductions and early discontinuation of treatment. CIN is characterised by the onset in late childhood or adulthood, affects mostly women, is clinically benign and has rare spontaneous remission. Here, we elucidate the challenges related to chronic neutropenia when administering chemotherapy through two clinical cases. Guidelines may need to be revised in order to optimise the treatment of patients with asymptomatic chronic neutropenia, thus personalising the medical decisions for each patient.