Ectopic thymoma of the chest wall
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《血管的通路杂志》
a Department of Cardiothoracic Surgery, Cardiothoracic Centre, Liverpool L14 3 PE, UK
b Department of Pathology, Royal Liverpool University Hospital, Liverpool, UK
Abstract
A case of ectopic thymoma arising from the chest wall is reported. A chest wall tumour involving the third and fourth ribs and extending extrapleurally and subpectorally was resected following a histopathological diagnosis of hemangioendothelioma obtained at initial incision biopsy. Pathological examination of the excised mass, revealed appearances consistent with a malignant thymoma. No primary thymic tumour was present in the anterior mediastinum so we conclude that the tumour originated in ectopic thymic tissue. To our knowledge a primary thymoma arising within the chest wall has not been reported.
Key Words: Ectopic thymoma; Chest wall
1. Introduction
Thymic epithelial tumours are the commonest tumours of the anterior mediastinum. Their occurrence outside the mediastinum albeit rare has been reported in the neck [1], thyroid [2], trachea [3], pulmonary parenchyma [4] and pleura [5]. To our knowledge thymoma arising from chest wall has not been previously described.
2. Case report
A 42-year-old man presented with a painless lump on the left anterior chest wall of 4 years duration. On examination there was a hard immobile tumour, measuring 6x5 cm attached firmly to the ribs and in close relation and to the left of the sternum. Chest CT (Fig. 1) revealed a destructive process involving the anterior end of the left third rib, with sclerotic centre and ragged margins. There was a large soft tissue component associated with the mass, extending into the anterior chest wall, stretching but not infiltrating the pectoral muscles. The mass also extended extrapleurally but the parietal pleura did not appear to be breached. There was no mediastinal lymphadenopathy, and no distant metastatic deposits. Bronchoscopy was normal. Open biopsy revealed features consistent with a hemangioendothelioma. The mass was approached using an anterolateral thoracotomy based on the margins of the pectoralis major muscle, to facilitate the mobilisation of the muscle. There was a 10x10 cm mass arising at the level of the third rib in the mid-clavicular line. It was visible on the internal aspect of the parietal pleura with separate nodules in the adjacent upper lobe of the left lung. The pectoral muscle was loosely involved in its innermost layer. The tumour extended to involve the intercostal muscles from the 1st to the 4th intercostal spaces. It also involved the left lateral border of the sternum.
The skin and uninvolved pectoral muscle were reflected laterally to expose the mass. The medial bony margins were resected to include the left lateral margin of the sternum. Ribs 2, 3, 4 were divided laterally in the mid-axillary line. The tumour was resected in entirety preserving ribs 1 and 5. The adjacent pulmonary nodules were resected separately using a stapler. The chest wall defect was reconstructed using a double layer of polypropylene mesh with orthopaedic cement sandwiched in between. Primary wound closure was achieved with the myocutaneous pectoral flap. The patient made an uneventful recovery from surgery but because of the locally advanced nature of the tumour he has subsequently received chemotherapy with six cycles of cyclophosphamide, doxorubicin and cisplatin. He has recently undergone an axillary clearance for metastatic thymic carcinoma to the left axillary lymph nodes.
3. Pathology
The resected specimen contained a firm, lobulated, grey mass measuring 8 cm in diameter, which appeared to surround the second and fourth ribs and destroy the mid part of the third. Externally, it was covered by muscle and connective tissue. Internally it elevated the parietal pleura to form a nodular mass, but did not appear to invade it. The ends of all three ribs were clear of tumour.
Microscopy showed nodules of varying sizes comprising a mixture of polygonal and spindle (epithelial) cells, associated with a dense lymphoplasmacytic infiltrate, vascular proliferation, nuclear pleomorphism, scanty mitoses, and tumour giant cells but no necrosis (Fig. 2). The polygonal and spindle cells stained positive for epithelial markers (AE1AE3 and MNF116). There were no CD 99 positive cells. Lymphocytes were a mixture of T and B cells identified by CD 3, 4, 5, 7, 8 and 20. A diagnosis of ectopic invasive thymoma was made, malignant in nature due to the pleomorphism, and aggressive presentation as evidenced by the destruction of the ribs. The initial incision biopsy, which showed features suggestive of a haemangioendothelioma, after review and using immunohistochemistry with epithelial markers was confirmed to be a thymoma, similar to the resected specimen.
4. Discussion
The two unsolved issues with respect to ectopic thymomas concern the origin of the tumours and their biological behaviour. The widely accepted explanation for unusually positioned thymomas is the neoplastic transformation of ectopic thymus tissue secondary to the aberrant descent of thymic tissue from the third or fourth branchial arch [6]. Investigators have failed to rationalise the presence of intrapulmonary and posterior mediastinal thymomas using this explanation. An alternative explanation is of a solitary metastasis from a small undetected primary tumour in the mediastinum [4]. Pathological studies on myasthenia gravis patients have shown that the thymic tissue can be widely distributed not only in the mediastinum but also at other sites including the neck or the pulmonary hila [6]. In the absence of any clinical or radiologically detected primary in the mediastinum or the pleura in our patient, the possibility of an ectopic thymomas secondary to aberrant descent appears more feasible.
Whether the criteria used for characterising classical thymomas arising in the mediastinum can be applied to ectopic thymomas is debatable. The rarity of the cases and incomplete follow up precludes any firm conclusions. Moran et al. [4] have described intrapulmonary thymomas to be slow growing and with good prognosis if surgically resected but in cases with cytological atypia adjuvant chemo/radiotherapy should be considered. Most reports of ectopic thymomas [7,8] have described well localised tumours amenable to surgical excision and resulting in a good prognosis with surgery alone. In patients with evidence of local advancement of the tumour, additional chemo/radiotherapy is desirable. With regard to anterior mediastinal thymomas it is widely acknowledged that their biological behaviour does not correlate with the histopathological appearances and attempts at finding some correlation have yielded controversial results [9]. Although most thymomas are encapsulated with a histologically bland appearance, some may be locally invasive or metastasize to distant organs.
Diagnosis of a thymoma depends on pattern analysis and confirmation by appropriate immunohistochemistry. In the present case, the histopathological appearances correlated with the clinical presentation, which was of a chest wall malignancy, its aggressive nature demonstrated by the destruction of ribs. In spite of the localised nature of the tumour and the disease free resection margin, because of the separate tumour nodules the patient has undergone adjuvant chemotherapy. Inspite of these measures the patient has presented with axillary metastasis to the left axilla.
Acknowledgement
Dr J R Gosney, Consultant Histopathologist, Royal Liverpool Hospital.
References
Martin JM, Randhawa G, Temple WJ. Cervical thymoma. Arch Pathol Lab Med 1986;110:354–7.
Asa SL, Dardrick I, Van Nostrand AW, Bailey DJ, Gullane PJ. Primary thyroid thymoma: a distinct clinicopathological entity. Hum Pathol 1988;19:1463–7.
Wadon A. Thymoma intratracheale. Zbl Allg Pathol Anat 1934;60:308–12.
Moran CA, Suster S, Fishback NF, Koss MN. Primary intrapulmonary thymoma-A clinicopathologic and immunohistochemical study of eight cases. Am J Surg Pathol 1995;19:304–12.
Attanoos RL, Galateau-Salle F, Gibbs AR, Muller S, Ghandour F, Dojcinov SD. Primary thymic epithelial tumours of the pleura mimicking malignant mesothelioma. Histopathology 2002;41:42–9.
Masaoka A, Nagaoka Y, Kotake Y. Distribution of thymic tissue at the anterior mediastinum: current procedures in thymectomy. J Thorac Cardiovasc Surg 1975;70:747–54.
Higashiyama M, Doi S, Kodama K, Yokuchi H, Tateishi R, Kuriyama K. Ectopic primary pleural thymoma: report of a case. Jpn J Surg 1996;26:747–50.
Honma K and Shimada K. Metastasising ectopic thymoma arising in the right thoracic cavity and mimicking diffuse pleural mesothelioma—An autopsy study of a case with review of literature. Wien Klin Wochenschr 1986;98:14–20.
Jain U and Frable WJ. Thymoma-Analysis of benign and malignant criteria. J Thorac Cardiovasc Surg 1974;67:310–21.(Krishnanand R. Pai, Vinut)
b Department of Pathology, Royal Liverpool University Hospital, Liverpool, UK
Abstract
A case of ectopic thymoma arising from the chest wall is reported. A chest wall tumour involving the third and fourth ribs and extending extrapleurally and subpectorally was resected following a histopathological diagnosis of hemangioendothelioma obtained at initial incision biopsy. Pathological examination of the excised mass, revealed appearances consistent with a malignant thymoma. No primary thymic tumour was present in the anterior mediastinum so we conclude that the tumour originated in ectopic thymic tissue. To our knowledge a primary thymoma arising within the chest wall has not been reported.
Key Words: Ectopic thymoma; Chest wall
1. Introduction
Thymic epithelial tumours are the commonest tumours of the anterior mediastinum. Their occurrence outside the mediastinum albeit rare has been reported in the neck [1], thyroid [2], trachea [3], pulmonary parenchyma [4] and pleura [5]. To our knowledge thymoma arising from chest wall has not been previously described.
2. Case report
A 42-year-old man presented with a painless lump on the left anterior chest wall of 4 years duration. On examination there was a hard immobile tumour, measuring 6x5 cm attached firmly to the ribs and in close relation and to the left of the sternum. Chest CT (Fig. 1) revealed a destructive process involving the anterior end of the left third rib, with sclerotic centre and ragged margins. There was a large soft tissue component associated with the mass, extending into the anterior chest wall, stretching but not infiltrating the pectoral muscles. The mass also extended extrapleurally but the parietal pleura did not appear to be breached. There was no mediastinal lymphadenopathy, and no distant metastatic deposits. Bronchoscopy was normal. Open biopsy revealed features consistent with a hemangioendothelioma. The mass was approached using an anterolateral thoracotomy based on the margins of the pectoralis major muscle, to facilitate the mobilisation of the muscle. There was a 10x10 cm mass arising at the level of the third rib in the mid-clavicular line. It was visible on the internal aspect of the parietal pleura with separate nodules in the adjacent upper lobe of the left lung. The pectoral muscle was loosely involved in its innermost layer. The tumour extended to involve the intercostal muscles from the 1st to the 4th intercostal spaces. It also involved the left lateral border of the sternum.
The skin and uninvolved pectoral muscle were reflected laterally to expose the mass. The medial bony margins were resected to include the left lateral margin of the sternum. Ribs 2, 3, 4 were divided laterally in the mid-axillary line. The tumour was resected in entirety preserving ribs 1 and 5. The adjacent pulmonary nodules were resected separately using a stapler. The chest wall defect was reconstructed using a double layer of polypropylene mesh with orthopaedic cement sandwiched in between. Primary wound closure was achieved with the myocutaneous pectoral flap. The patient made an uneventful recovery from surgery but because of the locally advanced nature of the tumour he has subsequently received chemotherapy with six cycles of cyclophosphamide, doxorubicin and cisplatin. He has recently undergone an axillary clearance for metastatic thymic carcinoma to the left axillary lymph nodes.
3. Pathology
The resected specimen contained a firm, lobulated, grey mass measuring 8 cm in diameter, which appeared to surround the second and fourth ribs and destroy the mid part of the third. Externally, it was covered by muscle and connective tissue. Internally it elevated the parietal pleura to form a nodular mass, but did not appear to invade it. The ends of all three ribs were clear of tumour.
Microscopy showed nodules of varying sizes comprising a mixture of polygonal and spindle (epithelial) cells, associated with a dense lymphoplasmacytic infiltrate, vascular proliferation, nuclear pleomorphism, scanty mitoses, and tumour giant cells but no necrosis (Fig. 2). The polygonal and spindle cells stained positive for epithelial markers (AE1AE3 and MNF116). There were no CD 99 positive cells. Lymphocytes were a mixture of T and B cells identified by CD 3, 4, 5, 7, 8 and 20. A diagnosis of ectopic invasive thymoma was made, malignant in nature due to the pleomorphism, and aggressive presentation as evidenced by the destruction of the ribs. The initial incision biopsy, which showed features suggestive of a haemangioendothelioma, after review and using immunohistochemistry with epithelial markers was confirmed to be a thymoma, similar to the resected specimen.
4. Discussion
The two unsolved issues with respect to ectopic thymomas concern the origin of the tumours and their biological behaviour. The widely accepted explanation for unusually positioned thymomas is the neoplastic transformation of ectopic thymus tissue secondary to the aberrant descent of thymic tissue from the third or fourth branchial arch [6]. Investigators have failed to rationalise the presence of intrapulmonary and posterior mediastinal thymomas using this explanation. An alternative explanation is of a solitary metastasis from a small undetected primary tumour in the mediastinum [4]. Pathological studies on myasthenia gravis patients have shown that the thymic tissue can be widely distributed not only in the mediastinum but also at other sites including the neck or the pulmonary hila [6]. In the absence of any clinical or radiologically detected primary in the mediastinum or the pleura in our patient, the possibility of an ectopic thymomas secondary to aberrant descent appears more feasible.
Whether the criteria used for characterising classical thymomas arising in the mediastinum can be applied to ectopic thymomas is debatable. The rarity of the cases and incomplete follow up precludes any firm conclusions. Moran et al. [4] have described intrapulmonary thymomas to be slow growing and with good prognosis if surgically resected but in cases with cytological atypia adjuvant chemo/radiotherapy should be considered. Most reports of ectopic thymomas [7,8] have described well localised tumours amenable to surgical excision and resulting in a good prognosis with surgery alone. In patients with evidence of local advancement of the tumour, additional chemo/radiotherapy is desirable. With regard to anterior mediastinal thymomas it is widely acknowledged that their biological behaviour does not correlate with the histopathological appearances and attempts at finding some correlation have yielded controversial results [9]. Although most thymomas are encapsulated with a histologically bland appearance, some may be locally invasive or metastasize to distant organs.
Diagnosis of a thymoma depends on pattern analysis and confirmation by appropriate immunohistochemistry. In the present case, the histopathological appearances correlated with the clinical presentation, which was of a chest wall malignancy, its aggressive nature demonstrated by the destruction of ribs. In spite of the localised nature of the tumour and the disease free resection margin, because of the separate tumour nodules the patient has undergone adjuvant chemotherapy. Inspite of these measures the patient has presented with axillary metastasis to the left axilla.
Acknowledgement
Dr J R Gosney, Consultant Histopathologist, Royal Liverpool Hospital.
References
Martin JM, Randhawa G, Temple WJ. Cervical thymoma. Arch Pathol Lab Med 1986;110:354–7.
Asa SL, Dardrick I, Van Nostrand AW, Bailey DJ, Gullane PJ. Primary thyroid thymoma: a distinct clinicopathological entity. Hum Pathol 1988;19:1463–7.
Wadon A. Thymoma intratracheale. Zbl Allg Pathol Anat 1934;60:308–12.
Moran CA, Suster S, Fishback NF, Koss MN. Primary intrapulmonary thymoma-A clinicopathologic and immunohistochemical study of eight cases. Am J Surg Pathol 1995;19:304–12.
Attanoos RL, Galateau-Salle F, Gibbs AR, Muller S, Ghandour F, Dojcinov SD. Primary thymic epithelial tumours of the pleura mimicking malignant mesothelioma. Histopathology 2002;41:42–9.
Masaoka A, Nagaoka Y, Kotake Y. Distribution of thymic tissue at the anterior mediastinum: current procedures in thymectomy. J Thorac Cardiovasc Surg 1975;70:747–54.
Higashiyama M, Doi S, Kodama K, Yokuchi H, Tateishi R, Kuriyama K. Ectopic primary pleural thymoma: report of a case. Jpn J Surg 1996;26:747–50.
Honma K and Shimada K. Metastasising ectopic thymoma arising in the right thoracic cavity and mimicking diffuse pleural mesothelioma—An autopsy study of a case with review of literature. Wien Klin Wochenschr 1986;98:14–20.
Jain U and Frable WJ. Thymoma-Analysis of benign and malignant criteria. J Thorac Cardiovasc Surg 1974;67:310–21.(Krishnanand R. Pai, Vinut)