Eur J Cardiothorac Surg 2004;26:1220-1222
© 2004 Elsevier Science NL
Bilateral thoracic extraadrenal myelolipoma
T. Franiela,
B. Fleischerb,
B.W. Raabc,
L. Füzesia,*
a Department of Pathology, Georg August University, Robert-Koch-Str. 40, D-37075 Göttingen, Germany
b Department of Surgery, Evangelisches Krankenhaus, Weende, Göttingen, Germany
c Department of Diagnostic Radiology, Georg August University, Göttingen, Germany
Received 4 May 2004;
received in revised form 30 July 2004;
accepted 3 August 2004.
* Corresponding author. Tel.: +49 551 396858; fax: +49 551 398627. (E-mail: fuezesi{at}med.uni-goettingen.de).
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Abstract
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Myelolipoma commonly occurs in the adrenal gland and is composed of both adipose tissue and normal hematopoietic elements. Extraadrenal myelolipoma may occur in the retroperitoneum, stomach, liver, lung, and in 3% of cases even in the mediastinum. We present a 65-year-old female patient with unspecific clinical symptoms. Routine chest roentgenograms revealed bilateral widening of the posterior mediastinum. Computed tomography showed bilateral, paravertebral lesions of 4.5 and 6.5cm in diameter, respectively. After surgical removal, bilateral thoracic myelolipoma was pathomorphologically diagnosed. The imaging differential diagnosis of bilateral solid lesions in the posterior mediastinum including lymph node metastases, lymphomas, neurogenic tumors and extramedullary hematopoietic tumors is discussed.
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1. Introduction
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The most frequent tumors of the posterior mediastinum in adults are metastatic neoplasms, neurogenic tumors (neurofibroma, neurilemmoma, malignant peripheral nerve sheath tumors), other soft tissue tumors and cystic tumors [1]. Herein we report on a rare case of a bilateral myelolipoma, extraadrenal myelolipoma (EAM) located in the posterior mediastinum in a 65-year-old female patient. Myelolipoma is encapsulated and of soft consistency composed of yellowish adipose tissue and reddish-brown tissue corresponding to hematopoietic or hemorrhages [2]. Myelolipoma is most commonly located unilaterally in the adrenal cortex [2]. In about 15% of cases myelolipomas occur extraadrenally [3]. The thorax, predominantly the posterior mediastinum [3,4], but occasionally even the lungs [5], may be affected in 3% of the cases. Thoracic EAM must be considered in preoperative differential diagnosis, to differentiate it, not only from extramedullary hematopoietic tumors but also from other tumors occurring at these sites such as lymph node metastases, lymphomas or neurogenic tumors [1,6].
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2. Case report
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A 65-year-old female patient was presented to the pulmonologist with productive cough. In her past medical history she had underwent appendectomy, tonsillectomy and total replacement of the left hip. Furthermore, she suffered from chronic gastritis caused by Helicobacter pylori and hypertension. She had been smoking 20 cigarettes per day for the last 15 years resulting in chronic obstructive bronchitis. Physical examination revealed a lipoma of 2cm in diameter below the right clavicula. Apart from slightly increased numbers of leucocytes (15,000/µl) the laboratory findings were within normal limits.
Routine posteroanterior chest roentgenograms showed widening of the mid posterior mediastinum (Fig. 1a). Computed tomography (CT) revealed two paravertebral masses with well-defined margins, well demarcated from the descending aorta in the posterior mediastinum. There was no destruction of adjacent bone structures, no pleural effusion or infiltration of surrounding tissues and no evidence of intraforaminal or intraspinal tumor manifestation. Following application of iodinated contrast media both lesions showed an inhomogeneous enhancement (Fig. 1b). The CT scan of the upper abdomen revealed no abnormalities of the liver, spleen or the retroperitoneum.
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Fig. 1. (a) Posteroanterior chest X-ray showing a bilateral mass in the posterior mediastinum. (b) Contrast-enhanced computed tomography scan showing a bilateral thoracic paravertebral mass. Note enhancement of the lesions with fatty areas of hypoattenuation.
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After left thoracotomy, a roundish, paravertebral, encapsulated solid mass of soft consistency measuring 4.5cm in diameter was removed. Three months later the right-sided lesion of 6.5cm in diameter was also excised. Grossly, both tumors disclosed a thin capsule of soft consistency and reddish-brown color. Histomorphologically, both tumors consisted of mature fat tissue and areas of regular hematopoiesis (Fig. 2). A bilateral thoracic EAM was diagnosed. The follow-up included physical examination, laboratory investigations, CT of the body. This revealed no recurrence or any other abnormalities after 12 months.
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Fig. 2. High power magnification (x400) shows adipocytes admixed with hemotopoietic elements, including megakaryocytes and cells of regular granulopoietic and erythropoietic cell lineages.
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3. Discussion
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Myelolipoma occurs at any age, however, patients with EAM are generally older (mean age 64 years) than patients with adrenal myelolipoma (mean age 55 years) [2]. EAM seems to be slightly overrepresented in female with a sex ratio of 1.5:1 [2]. Size of EAM ranges between 4 and 15cm with a mean diameter of 8.2cm [2]. Adrenal myelolipoma and EAM cause no specific symptoms [2,6,7]. In particular, no disorders of the peripheral blood or bone marrow were observed.
Paravertebral thoracic manifestation of EAM can usually be differentiated as a paravertebral soft tissue mass on routine roentgenograms from cardiac and vascular structures in the anterior and mid mediastinum. CT findings vary according to high-attenuation areas of predominantly myeloid elements and low-attenuation areas of adipose tissue [2,4].
Imaging differential diagnosis of bilateral thoracic EAM includes primary or secondary tumors of lymph nodes, neurogenic tumors, and rarely paravertebral thoracic extramedullary hematopoiesis [1,7]. The inhomogeneuos contrast enhancement in CT scan may raise suspicions for a high grade lymphoma or lymph node metastasis of a malignant tumor. In both cases, B symptoms should be expected. In the setting of von Recklinghausen disease, the inhomogeneuos contrast enhancement in CT scan may implicate neurofibromas with degenerative changes or malignant nerve sheeth tumors. If von Recklinghausen disease can be ruled out, paragangliomas and extraadrenal pheochromocytomas should also be considered. The most difficult differential diagnosis of myelolipoma is the extramedullary hematopoietic tumor, which is mostly associated with chronic anemia in the setting of hematologic disease [7,8]. Both tumors consist of varying amounts of myeloid and adipose tissue [7]. Extramedullary hematopoietic tumor occurs at multiple sites and is most commonly located in the thoracic paravertebral area, where it appears more lobulated and nestles against the costovertebral angle [6–8]. In contrast, characteristic features of myelolipoma are the solitary or in rare cases bilateral occurrence, the round or oval shape and the lack of anemia and hemoglobinopathy [6,7].
There is no agreement on how to manage EAM. Considering the potential progressive enlargement of the lesion and the uncertain preoperative diagnosis, most myelolipomas are surgically removed. However, the diagnosis of adrenal, presacral or mediastinal myelolipomas can preoperatively be verified by CT-guided fine needle biopsy with a high reliability [2,4]. In such cases regular radiological follow-up is an alternative way to avoid a surgical procedure.
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References
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- Dähnert W. Radiology review manual. Baltimore, MD: Williams and Wilkins; 1999p. 59–60 see also p. 100 and 101.
- Kawanami S, Watanabe H, Aoki T, Nakata H, Hayashi T, Kido M, Tsukada J, Eto S. Mediastinal myelolipoma: CT and MRI appearances. Eur Radiol 2000;10:691-693.[CrossRef][Medline]
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Abstract
1. Introduction
