Extra-adrenal paravertebral myelolipoma mimicking a thoracic schwannoma
- Jens Schittenhelm1,
- Simon N Jacob2,
- Joanna Rutczynska3,
- Ilias Tsiflikas4,
- Richard Meyermann5,
- Rudi Beschorner5
- 1University of Tuebingen, Calwer Str. 3, Tübingen 72076, Germany
- 2Department of Neurology, University of Tuebingen, Tübingen 72070, Germany
- 3Department of Pathology, University of Tuebingen, Tübingen 72070, Germany
- 4Department of Radiology, University of Tuebingen, Tübingen 72070, Germany
- 5Institute of Brain Research, University of Tuebingen, Tübingen 72070, Germany
- Jens Schittenhelm,
- Published 5 March 2009
Myelolipoma of the adrenal gland is composed of both adipose tissue and normal haematopoietic elements. Extra-adrenal myelolipomas are rare. We present the case of a 63-year-old female patient with adenoma of the adrenal gland and an additional paravertebral lesion in the thoracic spine. Previous computed tomography of the lesion covering the nerve roots in the right T8–T9 foramina was compatible with a schwannoma. Post-mortem histopathology showed the incidental finding of a paravertebral myelolipoma.
Myelolipomas are rare benign tumour-like lesions comprising mature fat and bone marrow elements and are typically observed in the adrenal glands. Most patients are over 40 years of age and there is a 2:1 female:male predominance. Usually small, these lesions tend to be asymptomatic and are incidental findings during surgery or autopsies. Enlargement may result in abdominal pain, constipation or nausea.
Spontaneous ruptures can cause massive retroperitoneal haemorrhage from the lesion. Extramedullary myelolipomas are rare and have been previously described in the mediastinum, mesentery and presacral regions.1 They must not be confused with extramedullary haematopoietic malignancies.
The patient was a 83-year-old female with a history of arterial hypertension, type 2 diabetes, hyperuricaemia, coronary artery disease and chronic obstructive pulmonary disease. Following an attack of severe headache and subsequent altered mental state she was immediately admitted to hospital. Neurological examination revealed paresis of the left facial nerve. A cranial computed tomography (CT) scan showed extensive subarachnoid haemorrhage. Cerebral angiography did not detect an aneurysm. Laboratory blood tests showed values within normal limits (haemoglobin 15.4 g/dl, haematocrit 43.7%). Seven days post-admission, she developed acute respiratory failure and became comatose.
Thoracoabdominal CT ruled out pulmonary embolism; however, CT showed an expansive lesion in the right adrenal gland and a paravertebral contrast-enhancing lesion located at the level of the eighth thoracic vertebra close to the right intervertebral foramen (fig 1). The radiological diagnosis of the paravertebral lesion was schwannoma. The patient died 6 days later following further cardiopulmonary deterioration. No invasive life-support treatment was initiated, respecting the wish of the patient.
Autopsy revealed pulmonary emphysema with associated oedema and bronchitis.
Cause of death was cardiorespiratory failure associated with extensive subarachnoid haemorrhage covering the brainstem and right parietal lobe. The abdominal lesion was histologically diagnosed as an adenoma of the right adrenal gland measuring 5.5×4.0×3.5 cm. No hepatosplenomegaly was seen. The bone marrow was not examined.
The paravertebral mass measured 2.5×4.0×2.0 cm and covered the nerve roots in the right T8–T9 foramina. It appeared soft and had a smooth and reddish coloured soft tissue capsule (fig 2). Cut fragments showed yellowish and friable red to purple areas corresponding microscopically to mature fat and blood-forming tissue. The latter had high cellularity and a regular myeloid to erythroid ratio of approximately 3:1, devoid of germinal centres (fig 3), leading to the diagnosis of myelolipoma.
The histogenesis of myelolipomas is unclear. There is a high incidence of associated adrenocortical lesions and hyperplasia2 suggesting hormonally driven growth. Some authors propose that the very rare extra-adrenal myelolipomas are based on metaplastic changes of ectopic-located choristomatous haematopoietic stem cell remnants.3 Radiological and intraoperative differential diagnosis should include, but not be limited to, schwannoma, neurofibroma, angiolipoma, epidural lipomatosis and teratoma.4 Magnetic resonance imaging is helpful in the diagnosis of cases showing an increased signal intensity on T1-weighted images, which are suggestive of interdispersed fat, mixed with focal regions of intermediate signal where blood-forming tissue predominates.5
Although rare, extra-adrenal myelolipoma should be included in the differential diagnosis of paravertebral lesions containing fatty tissue.
As there is a risk of spontaneous ruptures in larger myelolipomas, surgical resection has to be considered even in cases with asymptomatic lesions.
Competing interests: none.
Patient consent: Patient/guardian consent was obtained for publication.