A rare and unusual case of myeloid sarcoma in a paediatric patient

Abstract

Background: Myeloid sarcoma is an extramedullary growth of blasts in the myeloid lineage and often precedes or occurs simultaneously with the diagnosis of acute myeloid leukaemia (AML). It is rare and occurs in less than 1% of patients who have AML. In children, extramedullary involvement is most common in the skin and eyes. There have been other case reports of myeloid sarcoma involving the eyes, cardiac tissue, nasal tissue, gingiva and pancreas. This report highlights a rare case of myeloid sarcoma in a paediatric patient involving the breast, which occurred six months before the diagnosis of AML. Case Presentation: An eleven-year-old female patient was referred from a regional centre to a tertiary paediatric hospital with severe anaemia (Hb 28), thrombocytopenia (Pl 7), and blasts on blood film. She was found to have acute myeloid leukaemia, CD33 positive, RUNX1-RUNX1T1 (FISH) and CNS3 disease. She was commenced on the appropriate chemotherapy protocol (mitoxantrone, daunorubicin, gemtuzumab) and is currently in remission after year-long treatment. Preceding her presentation she described a six-month history of enlarging bilateral breast lumps. She presented to her general practitioner with concerns of breast lumps three months prior to the presentation but was told that her symptoms were benign as she was pre-pubertal. The breast lumps were not cyclical with her period and were not painful. On examination, she had multiple breast lumps on both breasts, hard in nature, non-tender and mobile. An ultrasound demonstrated multiple heterogeneous, hypoechoic masses, irregular in shape with indistinct margins and internal vascularity on colour Doppler. There was no obvious fluid component and no significant posterior acoustic enhancement or shadowing. The appearance was deemed atypical of fibroadenomata and, in the clinical context, likely myeloid sarcomas. One month post commencement of chemotherapy, a repeat ultrasound showed small residual hypoechoic area, which completely resolved on a subsequent scan post-treatment. This confirmed that her breast lesions were likely secondary to myeloid sarcoma of the breast. Learning Points Discussion: Breast lumps in adolescent children are mostly self-limiting and benign. However, this case highlights the importance of considering a rare diagnosis of malignancy. Owing to its rarity, we have a scarcity of research in this area. Further research by means of systematic reviews and randomised control trials will provide prognostic information and better treatment guidelines.L6368137482022-01-11 <br />