Ann Thorac Surg 2009;88:2001-2004. doi:10.1016/j.athoracsur.2009.05.042
© 2009 The Society of Thoracic Surgeons
Case Reports
Intrathoracic Extramedullary Haematopoiesis Manifested as a Neoplastic Lesion Within Anterior Mediastinum
Mario Santini, MD*,
Alfonso Fiorelli, MD, PhD,
Giovanni Vicidomini, MD, PhD,
Filomena Napolitano, MD
Thoracic Surgery Unit, Second University of Naples, Naples, Italy
Accepted for publication May 13, 2009.
* Address correspondence to Dr Santini, Thoracic Surgery Unit, Second University of Naples, Piazza Miraglia, 2, Naples, I-80138, Italy (Email: mario.santini{at}unina2.it).
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Abstract
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Intrathoracic extramedullary hematopoiesis (EMH), the formation of apparently normal blood cells outside the confines of the bone marrow, is an uncommon but well-defined entity. It is usually associated with hematologic disorders and located in the lower paravertebral sulci or rarely in the pleura. We report a case of EMH, which presented in a patient without hematologic disorders and was manifested as an anterior mediastinal mass. The first interesting aspect of our case was that EMH occurred in a patient with normal laboratory findings and no past medical history of anemia. The second remarkable characteristic was that EMH manifested as an anterior mediastinal mass, mimicking a neoplastic lesion. Definitive diagnosis of EMH was established by a video-assisted thoracoscopic surgical biopsy. In light of this diagnosis, no further surgical procedure was carried out.
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Introduction
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Intrathoracic extramedullary hematopoiesis (EMH) is a rare condition, but its pathologic features have been well established; this condition is usually accompanied by hematologic disorders and is situated in the posteroinferior mediastinum. We report a case of EMH presented in a patient with normal blood tests, yet manifested as an anterior mediastinal mass. Definitive diagnosis was established by video-assisted thoracoscopic surgical (VATS) biopsy.
A 57-year-old woman, without previous significant medical history, except for obesity, was admitted at another hospital for cough and dyspnea. Physical examination, blood tests, and laboratory tests were unremarkable. A chest roentgenogram showed a slight prominence of the superior mediastinum projected to the left (Fig 1A). A computed tomographic scan (CT) with contrast medium revealed a well-encapsulated homogeneous mass arising in the prevascular space at the level of the left innominate vein and extending to the level of the underface of the aortic arch (Fig 1B). No additional nodular opacities, no pathologically enlarged lymphonodes, and no lesions were seen in the lungs, liver, spleen, and adrenals. An Fluorine-18-2-fluoro-2-deoxyglucose positron emission tomographic scan showed increased uptake in the area of the anterior mediastinal mass (Fig 2A). Considering the potential for malignancy, the patient was referred to our institution for treatment of the mediastinal mass. Because differential diagnosis included several kinds of neoplastic lesion with special emphasis of lymphoma and thymoma, we performed a bronchoscopy, which revealed no lesions. A fine-needle aspiration (FNA) was also performed, but this did not provide sufficient material for a definitive diagnosis. Consequently, to avoid an unnecessary sternotomy, we performed an early VATS approach for biopsy. During the VATS approach, a soft and deep red mass was noted at the superior mediastinum that was distinct from the region of the thymus and projected to the left with no extension into the adjacent bone structure. After the biopsy there was low-pressure bleeding that stopped without any treatment. A pathologic report revealed foci of extramedullary hematopoiesis characterized by the presence of megakaryocites, erythroid colonies, and myeloid colonies. Occasional blood vessels and fat vacuoles supported by fibroconnective stroma were present (Fig 2B). The final diagnosis was EMH. In light of this diagnosis, no further surgical procedure was carried out. Afterward, a peripheral blood smear and an iliac crest bone marrow biopsy were performed, but these did not reveal evidence of any hematologic disorder or infiltration by neoplastic or fibrotic tissue. The patient was discharged on the postoperative day 5.
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Fig 1. (A) Chest roentgenogram showed a slight prominence of the superior mediastinum projected to the left. (B) A computed tomographic scan with contrast medium revealed a well-encapsulated homogeneous mass arising in the prevascular space at the level of the left innominate vein and extending to the level of the underface of the aortic arch.
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Fig 2. (A) An Fluorine-18-2-fluoro-2-deoxyglucose positron emission tomographic scan showed increased uptake in the area of the anterior mediastinal mass. (B) Photomicrograph illustrated hematopoietic tissue circumscribed by a thin fibrous capsule. Erythroid hyperplasia was present with megakaryocite and lipocytes (x400).
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Comment
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Intrathoracic EMH, the formation of appearently normal blood cells outside the confines of the bone marrow is uncommon, but is a well-defined entity [1]. It is usually asymptomatic and located in the lower paravertebral sulci or rarely in the pleura [2]. If hematologic disorder and radiologic evidence of myelofibrosis are present, EMH is easy to diagnose. In uncertain cases, diagnosis can only come from biopsy. Treatment of EMH is unnecessary in the absence of complication [1].
The first interesting aspect of our case is that EMH occurred in a patient without past medical history of anemia and with normal laboratory findings. Most cases of EMH have been associated with bone marrow dysfunction, but EMH extraordinarily may be presented in a patient without hematologic disorders, with only one case reported by Ghosh and colleagues [3] in literature. In our experience, the cough and dyspnea were the only symptoms probably due to the infiltrative nature of EMH foci, which formed small, multiple islets of hemopoietic tissue in the interstitial lung that may be unrecognizable at radiologic evaluation [4]. The second remarkable characteristic is that EMH manifested as an anterior mediastinal mass. In Thoracic Surgery [5] and General Thoracic Surgery [6], classic handbooks of lung diseases, EMH is not included in the list of possible causes of the mass located in the anterior mediastinum, whereas in literature there is only another case reported by Catinella and colleagues [7] who described a patient with EMH simulating anterior mediastinal tumor. In contrast to our case, the patient had incompletely characterized anemia and diagnosis, which was established after excision of the tumor with a median sternotomy. In our experience, the location of EMH obscured the origin and differential diagnosis, which was more focused on the likelihood of this mass being lymphoma or thymoma rather than any other disease. Noninvasive procedures were unable to establish the diagnosis because a computed tomographic scan revealed a well-encapsulated homogeneous mass, which is a possible feature of lymphoma or thymoma, or both, whereas an Fluorine-18-2-fluoro-2-deoxyglucose positron emission tomographic scan uptake of the mass suspected a diagnosis of malignancy [5]. In addition, an invasive procedure (ie, a fine-needle aspiration along with broncoscopy) provided insufficient material for definitive diagnosis. Thus, starting with a VATS approach to a biopsy was preferred to avoid an unnecessary sternotomy, in case of any histologic diagnosis of lymphoma. The VATS approach was considered more feasible than the mediastinotomy approach, considering the obesity of the patient. In addition, the VATS approach carries the same advantages of an open biopsy because of direct visualization of the mass, and on the other hand, any hemorrhage that results from the biopsy can be better controlled compared with the percutaneous needle biopsy. During the VATS procedure, we performed a surgical biopsy rather than a core-needle biopsy to avoid the likelihood of inadequate tissue for a diagnosis of lymphoma or thymoma, or both.
In conclusion, we wish to emphasize in our report that the radiographic appearance of an anterior mediastinal mass does not prove its malignancy. Thus, to avoid an unnecessary sternotomy in doubtful cases, the diagnosis of these masses may be achieved by using the VATS approach to biopsy.
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References
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- Chu KA, Lai RS, Lee CH, Lu JY, Chang HC, Chiang HT. Intrathoracic extramedullary haematopoiesis complicated by massive haemothorax in alpha-thalassaemia Thorax 1999;54:466-468.[Abstract/Free Full Text]
- Kupferschmid JP, Shahian DM, Villanueva AG. Massive hemothorax associated with intrathoracic extramedullary hematopoiesis involving the pleura Chest 1993;103:974-975.[Abstract/Free Full Text]
- Ghosh AK, Pawade J, Standen GR, Lang-Lazdunski L. Primary extramedullary hematopoiesis manifesting as massive bilateral chylothorax Ann Thorac Surg 2005;80:1515-1517.[Abstract/Free Full Text]
- Yusen RD, Kollef MH. Acute respiratory failure due to extramedullary hematopoiesis Chest 1995;108:1170-1172.[Abstract/Free Full Text]
- Pearson FJ, Cooper JD, Deslauriers J, et al. Thoracic Surgery2nd ed.. New York, NY: Churchill Livingstone; 2002.
- Shields TW, LoCicero J, Ponn RB, et al. General Thoracic Surgery5th ed.. Philadelphia, PA: Lippincott Williams & Wilkins; 2000.
- Catinella FP, Boyd AD, Spencer FC. Intrathoracic extramedullary hematopoiesis simulating anterior mediastinal tumor J Thorac Cardiovasc Surg 1985;89:580-584.[Abstract]
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Abstract
Introduction
