Background

Acute myeloid leukaemia corresponds to malignant monoclonal proliferation of medullary blastic myeloid cells with an interrupted differentiation [1]. Clinically acute myeloid leukaemia will result in adenopathy and hepatosplenic syndrome associated with bone marrow failure syndrome. Extra nodal involvement is rare and mostly made of frequently observed forms of lymphoblastic leukemia in children. These attacks represent 2 to 8 % of acute myeloid leukaemia. Epidural localization is unusual and is a rare cause of spinal cord compression. Spinal cord compression as an initial presentation of acute myeloid leukaemia is extremely rare. In this study, we did not consider Spinal cord compression as the initial presentation of acute biphenotypic leukaemia [2]. The authors reported a case of acute myeloid leukaemia revealed by thoracic spinal cord compression. Literature review follows the case report.

Clinical case

A 17-year –old A black patient with no known significant medical history, complained of a 3-week history of inter-scapular back pain progressively exacerbating with insomnia associated with paraesthesia, hypoesthesia of the lower limbs and trunk. The rapidly worsening deficit led to emergent Neurosurgery consultation. Neurological examination found an almost paraplegic patient with increased deep tendon reflexes, a bilateral Babinski, a distended bladder, hypoesthesia and dysesthesia with at T10 sensitive level. Further clinical examination found no evidence of lymphadenopathy or hepatosplenomegaly. The diagnosis of spinal cord compression was made and a spinal CT scan showed an extensive epidural mass at T4-T9. MRI confirmed the presence of a thoracic epidural mass posterior to the spinal cord between T4 and T9 (Fig. 1a, b, c, d, e, f). The MR imaging showed hypointense lesion on T1 weighted sequence, isointense on T2 weighted sequence and enhanced on T1 with gadolinium. There was a distinct line of dura demarcation between the tumor mass and the spinal cord.

Fig. 1
figure 1

Spine MRI showing spinal cord compression at T4-T9 level by posterior epidural mass. a Sagittal view showing a T4T9 posterior mass which is isointense on T2 weighted sequence. b Sagittal view T1 sequence showing a hypointense T4T9 posterior lésion well demarcated from the dura. c Sagittal view showing a contrast enhancement of the T4-T9 lesion. d Axial view: The lesion is hypointense on T1 weighted sequence. e Axial view: The lesion is isointense on T2 sequence at the level of T5. f Axial view showing the enhancing lesion at the level of T5 wth a good demarcation from the dura

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Full blood count revealed leucocytosis with a importantly increased white blood cell count 200,000/mm3, with 77 % blasts, haemoglobin: 10.7 g/dL-1; platelet count: 102 × 109 L-1. The myelogram diagnosis was acute myelogenous leukaemia. Histologically the tumor is composed of immature cells. There are some immature eosinophile and neutrophile. Cytogenetic evaluation could not be done. Additional blood test did not find bleeding disorders or ion anomaly. Given the severity of the neurological picture and predicted rapid deterioration, a laminectomy from T4 to T10 was performed in emergency and found that the posterior epidural space was occupied by greyish, haemorrhagic tumour tissue, completely separated from the dura and pushes forwards. A macroscopically complete tumour resection was performed. Haemostasis was difficult. Histopathological examination of the tumour mass was favourable to leukemic blast cells. It was type 2 leukemia (Fig. 2). Advanced treatment of acute myeloid leukaemia was indicated. But the patient died a week after the diagnosis of spinal cord compression because of sepsis.

Fig. 2
figure 2

HE X 100: Tumor proliferation with blasts exhibiting cytonuclear atypia (a). Immunohistochemistry X 200: Nuclear expression of antibodies anti myeloperoxidase (MPO) by the majority of undifferentiated blasts (b)

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Discussion

The spinal cord compression revealing acute myeloid leukaemia is unusual. Nine cases have been reported from 2005 to 2015 [3–11] (Table 1). It often appears like a solid tumour known as granulocytic sarcoma or myeloid, or also chloroma as seen in our patient [12]. It corresponds to the migration outside of the bone marrow of myeloid cells that proliferate on their own [1]. The first case was described in 1811 by Burns in 1893 and Dock who reported its association with leukaemia [13, 14]. It is reported in 3.1 to 9.1 % of patients with acute myeloid leukaemia [15]. We found ten cases from 2005 to 2015 which were reported in literature. In those cases epidural space was occupied by granulocyt sarcoma [3-9 11, 15]. Surgically excision of the tumour appeared to be the first treatment option in these cases. Granulocytic sarcoma is frequently diagnosed simultaneously with or after the start of an acute myeloid leukaemia or may be the initial sign of a relapse in a patient in remission [3–9, 11, 15]. In non-leukemic patients, myeloid granulocytic sarcoma usually precedes acute myeloid leukaemia [16]. In 87 to 88 % of patients without hematologic abnormalities at diagnosis, acute myeloid leukaemia develops in the 10.5 to 11 following months [17]. Myeloid sarcoma may occur in all tissues but they are frequently localized on the skin, bone, soft tissues of the head and neck (especially on the orbit) and adenopathies [18]. Spinal localization and especially epidural is rare. Thoracic localization is the most frequent spinal localization followed by lumbar and sacral localizations. Clinical signs are in most cases made of spinal cord compression. Sometimes they involve isolated rachialgia [3–9, 11, 15]. MRI is the best choice for neuroimaging examination to show epidural tumour lesions. It is also the best neuroimaging examination [3–9, 11, 15] to show the epidural tumour lesions without being specific. Granulocytic sarcoma is iso-intense in T1 and T2 with in general a contrast enhancement [3–9, 11, 15]. The therapeutic strategy of this myeloid sarcoma is based on chemotherapy, radiation therapy, surgical decompression and bone marrow transplantation and any combination of these methods [3–9, 11, 15]. 1n cases of granulocytic sarcoma in particular by acute myeloid leukaemia with neurological signs, priority should be given to chemotherapy and/or radiation therapy rather than surgery. In our patient the diagnosis of acute myeloid leukaemia was made from full blood count after surgery. Surgery was only justified by the acuteness and quickly worsening neurological disorders. Despite some cases of more or less complete neurological recovery with a variable remission, most patients present with neurological sequellae and die from haematological complications dominated by sepsis.

Table 1 Literature review from 2005 to 2015. characterization of acute myeloid leukemia associated to spinal cord compression
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Conclusion

This case associated with the literature review has shown that granulocytic sarcoma with acute myeloid leukaemia should be considered as part of epidural spinal cord compression .it might be the initial sign of epidural spinal cord compression . Therefore surgery is indicated in emergency. Chemotherapy and radiotherapy are secondly introduced according to the diagnosis.