Myeloid sarcoma with ulnar nerve entrapment: A case report

Abstract

Background: Myeloid sarcoma (MS) is relatively rare, occurring mainly in the skin and lymph nodes, and MS invasion of the ulnar nerve is particularly unusual. The main aim of this article is to present a case of MS invading the brachial plexus, causing ulnar nerve entrapment syndrome, and to further clinical understanding of the possibility of MS invasion of peripheral nerves.

Case summary: We present the case of a 46-year-old man with a 13-year history of well-treated acute nonlymphocytic leukaemia who was admitted to the hospital after presenting with numbness and pain in his left little finger. The initial diagnosis was considered a simple case of nerve entrapment disease, with magnetic resonance imaging showing slightly abnormal left brachial plexus nerve alignment with local thickening, entrapment, and high signal on compression lipid images. Due to the severity of the ulnar nerve compression, we surgically investigated and cleared the entrapment and nerve tissue hyperplasia; however, subsequent pathological biopsy results revealed evidence of MS. The patient had significant relief from his neurological symptoms, with no postoperative complications, and was referred to the haemato-oncology department for further consultation about the primary disease. This is the first report of safe treatment of ulnar nerve entrapment from MS. It is intended to inform hand surgeons that nerve entrapment may be associated with extramedullary MS, as a rare presenting feature of the disease.

Conclusion: MS invasion of the brachial plexus and surrounding tissues of the upper arm, resulting in ulnar nerve entrapment and degeneration with significant neurological pain and numbness in the little finger, is uncommon. Surgical treatment significantly relieved the patient's nerve entrapment symptoms and prevented further neurological impairment. This case is reported to highlight the rare presenting features of MS.

Keywords: Acute nonlymphocytic leukaemia; Case report; Myeloid sarcoma; Sarcoma; Ulnar nerve entrapment syndrome; Upper limb surgery.

Figure 1

X-ray and magnetic resonance images. A and B: No significant abnormality on antero-posterior (A) and lateral (B) X-rays of the left elbow joint; C and D: Sagittal (C) and coronal (D) magnetic resonance images (MRI) showing significant abnormal signal in the left brachial plexus; E and F: Coronal MRI showing significant abnormal signal in the left brachial plexus. The red arrow points to the lesion.

Figure 2

Intraoperative and histological images. A: Intraoperative thickening and degeneration of the left ulnar nerve; B: Hematoxylin and eosin-stained section showing neuroepithelial and lymph node pathology.

Figure 3

Histopathology of myeloid sarcoma. Immunopathological examination shows tissue of lymphohaematopoietic lineage. A: CD21; B: Ki-67; C: LCA; D: MPO; E: CD117; F: CD34.