Interactive CardioVascular and Thoracic Surgery Advance Access published May 2, 2015
Cite this article as: Lin F, Pu Q, Ma L, Liu C, Mei J, Liao H et al. Surgical treatment of primary mediastinal myelolipoma. Interact CardioVasc Thorac Surg 2015; doi:10.1093/icvts/ivv112.
Surgical treatment of primary mediastinal myelolipoma Feng Lina,b, Qiang Pua, Lin Maa, Chengwu Liua, Jiandong Meia, Hu Liaoa, Zhilan Xiaoa, Chenglin Guoa and Lunxu Liua,* a b
Department of Thoracic Surgery, West China Hospital, Sichuan University, Chengdu, China Department of Thoracic Surgery, Affiliated Hospital of Guizhou Medical University, Guiyang, China
* Corresponding author. No. 37, Guoxue Alley, Chengdu, Sichuan 610041, China. Tel: +86-28-85422494; fax: +86-28-85422494; e-mail: [email protected] (L. Liu). Received 28 January 2015; received in revised form 27 March 2015; accepted 8 April 2015
Abstract OBJECTIVES: Primary mediastinal myelolipoma (PMM) is a rare benign tumour composed of haematopoietic tissue and mature adipose tissue. Here, we report the largest series aiming to investigate the outcomes of surgical treatment for patients with PMM. METHODS: We retrospectively reviewed the data of 12 patients operated in a single institute during the period between April 2008 and December 2014. RESULTS: There were 7 female and 5 male patients between 54 and 73 years old (median age, 64 years). Among them, 11 patients underwent unilateral (n = 10) or bilateral (n = 1) mass resection via video-assisted thoracic surgery (VATS), and 1 patient underwent a planned open thoracotomy due to a large tumour volume. The VATS operating time ranged from 20 to 65 min (median, 30 min) and intraoperative blood loss ranged from 20 to 60 ml (median, 30 ml). The open thoracotomy operating time was 120 min, and the blood loss was 1000 ml; thus, the patient received blood transfusion (2 units of RBCs). No operative mortalities or major postoperative complications were observed. All patients experienced a regular follow-up ranging from 2 to 80 months with a median follow-up of 18 months. No recurrence was observed at the time of evaluation. CONCLUSIONS: Surgical treatment is recommended for the diagnosis and treatment of PMM, while VATS is a safe and feasible option in most cases. Keywords: Mediastinum • Myelolipoma • Video-assisted thoracic surgery • Thoracotomy • Prognosis
INTRODUCTION
MATERIALS AND METHODS
Myelolipoma is a rare mesenchymal tumour composed of an admixture of mature adipose tissue and bone marrow cells. This tumour was first discovered by Gierke in 1905 and named myelolipoma by Oberling in 1929 [1]. Henceforward, reports on myelolipoma gradually increased. Myelolipoma is often encountered in the adrenal gland, while the mediastinal location is extremely unusual. A primary mediastinal myelolipoma (PMM) is often asymptomatic and detected during routine X-ray or computed tomographic (CT) examination as incidentalomas. A review of the literature revealed that only some single case reports have been reported to date. To our knowledge, this study involves the largest series of surgically treated patients with PMM from a single institute. In this study, we summarize our knowledge in an attempt to present a surgical treatment strategy for PMM.
Patients There were 7 female and 5 male patients between 54 and 73 years old (median age, 64 years). Among them, 5 male patients were current smokers, and the rest were non-smokers. Most patients were referred to our hospital asymptomatically, while the other 4 patients were presented with cough, back pain or fever. Seven patients were presented with combined diseases. The demographic and clinical characteristics of these patients are listed in Table 1.
Preoperative assessment All of the patients received routine laboratory studies, respiratory function tests, electrocardiography, X-ray and CT of the thorax
© The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
ORIGINAL ARTICLE
ORIGINAL ARTICLE – THORACIC
Interactive CardioVascular and Thoracic Surgery (2015) 1–5 doi:10.1093/icvts/ivv112
F: female; M: male; RPM: right posterior mediastinum; LPM: left posterior mediastinum; BPM: bilateral posterior mediastinum; T-VATS: triportal video-assisted thoracic surgery; U-VATS: uniportal video-assisted thoracic surgery.
22 15 13 9 7 5 2 4.0 × 3.0 3.0 × 2.0 4.0 × 3.0 6.5 × 4.0 3.0 × 2.0 5.0 × 4.0 14 × 12 61 63 61 65 65 54 65 6 7 8 9 10 11 12
M M F F F F M
No Yes No No No No Yes
None Cough None None Fever None None
RPM LPM RPM RPM RPM LPM LPM
Myelolipoma Myelolipoma Myelolipoma Neurogenic tumour Pleural tumour Myelolipoma Teratoma
T-VATS T-VATS T-VATS T-VATS T-VATS T-VATS Thoracotomy
20 25 35 30 25 20 120
30 20 50 40 30 20 1000
No 21 RPM 67 5
F
No
None
Hypertension, diabetes, hypothyroidism Diabetes None Hypertension Diabetes None Anaemia None
Pheochromocytoma
U-VATS
20
100
No No No No 80 80 56 31 20 50 30 60 35 50 30 65 T-VATS T-VATS T-VATS T-VATS
2.5 × 2.0 4.0 × 3.0 5.0 × 4.0 7.0 × 5.5; 3.8 × 2.8 2.0 × 2.0 RPM RPM LPM BPM 71 73 63 54 1 2 3 4
F M M M
No Yes Yes Yes
None None Back pain Cough
Diabetes None Thrombopenia None
Pleural tumour Neurogenic tumour Neurogenic tumour Neurogenic tumour
Recurrence Follow-up (months) Blood loss (ml) Time of op (min) Operation Preoperative diagnosis Size (cm) Location Accompanied disease Symptoms Smoking Sex Age No.
Table 1: Clinical features of PMMs in the study
No No No No No No No
F. Lin et al. / Interactive CardioVascular and Thoracic Surgery
2
before operation. CT scans revealed unilateral or bilateral encapsulated, well-circumscribed posterior mediastinal tumour (Fig. 1). The CT density ranged from −60.0 to +10.0 Hounsfield units. All tumours had no calcification. The major axis of the tumours ranged from 2 to 14 cm (median, 4 cm). Eleven patients had a single mass (7 located in the right and 4 located in the left), and 1 patient had bilateral masses. Given the lack of distinct clinical and imaging characteristics, only 4 patients were diagnosed with PMMs preoperatively, whereas the other patients were diagnosed with neurogenic tumour, parietal pleura tumour, pheochromocytoma or teratoma, respectively. Informed consent for the operation was obtained from all the patients before surgery. Retrospective review of the medical records was approved by the Institutional Review Board (IRB) of West China Hospital.
Surgical procedures The operations were carried out under general anaesthesia with single-lung ventilation. The lateral decubitus position or semipronation (lateral decubitus position with 30° forerake) was used. The surgical approach [video-assisted thoracic surgery (VATS) or thoracotomy] was determined according to the size and local invasion of each tumour. The VATS procedure included triportal and uniportal access. The incisions of triportal VATS included a 1-cm thoracoscopic port on the middle axillary line in the seventh intercostal space (ICS) and two 1.5-cm incisions on the anterior axillary line in the fourth and eighth ICS, respectively. For a uniportal procedure, a 3-cm incision was made on the middle axillary line in the seventh ICS with the patient placed in a semiprone position. During the VATS procedure, the surgeon stood on the ventral side of the patient to perform the operation with endoscopic suction and an electric coagulation hook. During the process, endoscopic suction was used for manipulating the tumour and suctioning away the blood and smoke to provide a clear surgical field. In contrast, the surgeon stood at the back of the patient to perform open thoracotomy. The benign nature of each tumour was confirmed by an intraoperative frozen section. All postoperative diagnoses were verified pathologically.
RESULTS Detailed information of each patient is listed in Table 1. Eleven patients underwent unilateral (n = 10) or bilateral (n = 1) mass resection via VATS, while the remaining 1 patient underwent planned open thoracotomy due to the large tumour volume. Ten patients underwent triportal VATS procedures and 1 patient underwent a uniportal VATS procedure successfully (Video 1). Serious pleural adhesions were detected in 3 patients. One patient suffered intercostal artery injury. The VATS operating time ranged from 20 to 65 min (median, 30 min) and the intraoperative blood loss ranged from 20 to 60 ml (median, 30 ml). The open thoracotomy operating time was 120 min, and the blood loss was 1000 ml; thus, the patient received blood transfusion (2 units of RBCs). No operative mortalities or major postoperative complications were observed. Pathological confirmation was based on routine light microscopic sections stained by haematoxylin and eosin (H&E). The tumours were composed of adipose tissue and haematopoietic elements (Fig. 2). All the patients underwent a regular follow-up ranging from 2–80 months
3
ORIGINAL ARTICLE
F. Lin et al. / Interactive CardioVascular and Thoracic Surgery
Figure 1: (A–D) Chest CT scans of 4 patients revealed the different, well-circumscribed posterior mediastinal tumours with uneven density on the right or left side of the vertebrae, respectively (arrows).
Video 1: Uniportal VATS resection for a primary mediastinal myelolipoma in the right posterior mediastinum.
(median, 18 months). No recurrence has been observed at the time of evaluation.
DISCUSSION PMM is a rare benign tumour, which is composed of mature adipose tissue and haematopoietic elements, and it is more often located at the right posterior mediastinum. Most cases are asymptomatic and detected incidentally during regular physical examination just like our cases. Only a few patients may present with unspecific symptoms, such as back pain and cough. A review of
the literature [2–14] in Table 2 and the results of our cases revealed that PMMs were more frequently detected in the elderly. It is generally agreed upon that CT is the most common and useful method for the diagnosis of PMM. This tumour often presents as an encapsulated and well-circumscribed tumour consisting of fatty tissue density, mixed with haematopoietic tissue appearing as partial high-density areas on CT. If the boundary between the tumour and the adjacent vital organs, such as the aorta, oesophagus or intervertebral foramen, cannot be clearly identified, supplementary MRI can provide additional information regarding the nature and extent of the tumour, which is useful for surgeons to evaluate the resectability and design surgical procedures. No characteristic finding can lead to a preoperative diagnosis of PMM, which should be distinguished from other similar tumours, including neurogenic tumours, lymphomas, malignant mesotheliomas and extramedullary haematopoietic tissue. Among these tumours, the distinction between myelolipoma and extramedullary haematopoietic tumours is important. Histologically, myelolipoma is composed of abundant fat tissue and a small amount of normal haematopoietic element. In contrast, extramedullary haematopoietic tumours show markedly different characteristics with abnormal haematopoietic components, and erythroid hyperplasia is common. In addition, most patients with extramedullary haematopoietic tumours usually present with some primary blood system diseases, such as hereditary spherocytosis and mediterranean anaemia, which also play a role in the differential diagnosis of myelolipoma.
F. Lin et al. / Interactive CardioVascular and Thoracic Surgery
4
Figure 2: The tumour composed of mature adipose tissue and haematopoietic elements (H&E staining, A: ×100; B: ×200).
Table 2: Reported cases of PMMs in the past 20 years No.
Author [ref.]
Time
Age
Sex
Size (cm)
Number
Location
Treatment
Follow-up
1 2 3 4 5 6 7 8 9 10 11 12 13
Wyttenbach et al. [3] Minamiya et al. [4] Koizumi et al. [5] Kawanami et al. [6] Gao et al. [7] Franiel et al. [2] Mohan et al. [8] Rossi et al. [9] Vaziri et al. [10] Geng et al. [11] Ema et al. [12] Fonda et al. [13] Nakagawa et al. [14]
1994 1997 1999 2000 2002 2004 2006 2007 2008 2013 2013 2013 2014
53 59 55 72 59 65 46 73 56 68 68 64 79
M M M M M F M F M F M F M
8.0 × 6.0 × 6.0 6.5 × 5.3 × 3.5 w4.0 Not stated 3.0 × 2.0 w4.5; w6.5 w4.5 w7.0 20 × 15 × 10 3.1 × 10; 2.5 × 9.0 Not stated 1.4 × 2.5 × 3.0 7.5 × 4.5 × 3.0; 1.9 × 1.5 × 1.1; 4.0 × 3.4 × 1.5
Single Single Single Multiple Single Multiple Single Single Single Multiple Single Single Multiple
RMM RPM PM BPM RPM BPM RAM LPM RPM BPM RPM LPM BPM
Thoracotomy Thoracotomy VATS Needle biopsy Thoracotomy Thoracotomy Thoracotomy Thoracotomy Thoracotomy Thoracotomy VATS VATS VATS
Not stated No recurrence Alive Not stated Not stated Alive Alive Not stated Dead Alive Alive Alive Alive
F: female; M: male; RAM: right anterior mediastinum; RPM: right posterior mediastinum; RMM: right middle mediastinum; LPM: left posterior mediastinum; BPM: bilateral posterior of mediastinum; PM: posterior mediastinum; VATS: video-assisted thoracic surgery.
There is still controversy about the surgical indication of PMM. Kawanami et al. [6] proposed that if a definitive diagnosis was established through CT-guided needle biopsy, surgery was unnecessary for asymptomatic patient. Kenney et al. [15] proposed that such tumours should be resected if they have grown to more than 10 cm in diameter. Recently, surgeons have recognized the potential of progressive enlargement of the tumour, and that a delayed surgery may cause more trauma and risks, particularly in elderly patients. Hence, an increasing number of patients have received surgical therapy in the early stage and gained ideal outcomes [10–13]. Considering the risks of haemorrhage and pneumothorax, we propose that biopsy is unnecessary when surgery is deemed necessary. Thus, no patient underwent CT-guided biopsy preoperatively in our study. The minimally invasive VATS has become a widely accepted alternative for the resection of mediastinal tumours. However, there are only a few case reports about application of VATS for PMM due to the low morbidity. In this study, we presented the largest case series of PMM patients undergoing VATS resection successfully. Triportal VATS was the most commonly used procedure.
Compared with open thoracotomy, this minimally invasive procedure was related with many advantages, such as less trauma, faster recovery, etc. With the development of thoracoscopic instruments and techniques, we also attempted to apply uniportal VATS for one case. To facilitate the operation through only one access, the patient’s position was adjusted from lateral to semiprone. Thus, the posterior mediastinum was exposed better with the pulmonary lobes falling forwards. Under this condition, only three instruments were inserted into the thoracic cavity at the same time, which reduced mutual interference between different instruments. Our study presented a satisfactory clinical outcome including shorter operating time and less blood loss. Based on our own experience and reports in the literature, we proposed that most PMMs with size ≤8 cm can be successfully resected via VATS. During operations, we also noted that PMM was a tumour with rich blood supplies, which arose predominantly from the branches of the aorta or intercostal arteries. The main difficulty during resection of PMMs via VATS lies in how to safely divide these vessels. In 1 case, an intercostal artery was injured accidentally and caused bothersome bleeding. Fortunately, the bleeding
was stopped successfully via compression and electrocoagulation. In addition, pleural adhesions were common in cases with a largesized tumour, which also increased the difficulty of operation. In the open thoracotomy, the large tumour accompanied by severe adhesions resulted in excessive intraoperative bleeding; therefore, an open thoracotomy was more suitable for the resection of tumours of larger size.
CONCLUSIONS In conclusion, this is the largest case series demonstrating that VATS is safe and feasible for the surgical treatment of PMMs with satisfactory clinical outcomes. The less invasive technique of uniportal VATS is a promising alternative. Further studies are needed to better understand the features of PMM. Conflict of interest: none declared.
REFERENCES [1] Plaut A. Myelolipoma in the adrenal cortex; myeloadipose structures. Am J Pathol 1958;34:487–515.
5
[2] Franiel T, Fleischer B, Raab BW, Fuzesi L. Bilateral thoracic extraadrenal myelolipoma. Eur J Cardiothorac Surg 2004;26:1220–2. [3] Wyttenbach R, Fankhauser G, Mazzucchelli L, Probst P. Primary mediastinal myelolipoma: a case report. Eur Radiol 1994;4:492–5. [4] Minamiya Y, Abo S, Kitamura M, Izumi K. Mediastinal extraadrenal myelolipoma: report of a case. Surg Today 1997;27:971–2. [5] Koizumi J, Harada H, Yamamoto N, Shiiku C, Ogasa T, Takahashi M et al. A case of mediastinal myelolipoma. Kyobu Geka 1999;52:869–71. [6] Kawanami S, Watanabe H, Aoki T, Nakata H, Hayashi T, Kido M et al. Mediastinal myelolipoma: CT and MRI appearances. Eur Radiol 2000;10: 691–3. [7] Gao B, Sugimura H, Sugimura S, Hattori Y, Iriyama T, Kano H. Mediastinal myelolipoma. Asian Cardiovasc Thorac Ann 2002;10:189–90. [8] Mohan K, Gosney JR, Holemans JA. Symptomatic mediastinal myelolipoma. Respiration 2006;73:552. [9] Rossi M, Ravizza D, Fiori G, Trovato C, Renne G, Miller MJ et al. Thoracic myelolipoma diagnosed by endoscopic ultrasonography and fine-needle aspiration cytology. Endoscopy 2007;39(Suppl 1):E114–5. [10] Vaziri M, Sadeghipour A, Pazooki A, Shoolami LZ. Primary mediastinal myelolipoma. Ann Thorac Surg 2008;85:1805–6. [11] Geng C, Liu N, Yang G, Qi M, Chen W. Primary mediastinal myelolipoma: a case report and review of the literature. Oncol Lett 2013;5:862–4. [12] Ema T, Kawano R. Myelolipoma of the posterior mediastinum: report of a case. Gen Thorac Cardiovasc Surg 2014;62:241–3. [13] Fonda P, de Santiago E, Guijarro M, Gamallo C. Mediastinal myelolipoma with leukocytosis. BMJ Case Rep 2013;2013. pii: bcr2013010349. [14] Nakagawa M, Kohno T, Mun M, Yoshiya T. Bilateral video-assisted thoracoscopic surgery resection for multiple mediastinal myelolipoma: report of a case. Korean J Thorac Cardiovasc Surg 2014;47:189–92. [15] Kenney PJ, Wagner BJ, Rao P, Heffess CS. Myelolipoma: CT and pathologic features. Radiology 1998;208:87–95.
ORIGINAL ARTICLE
F. Lin et al. / Interactive CardioVascular and Thoracic Surgery
Cite this article as: Lin F, Pu Q, Ma L, Liu C, Mei J, Liao H et al. Surgical treatment of primary mediastinal myelolipoma. Interact CardioVasc Thorac Surg 2015; doi:10.1093/icvts/ivv112.
Surgical treatment of primary mediastinal myelolipoma Feng Lina,b, Qiang Pua, Lin Maa, Chengwu Liua, Jiandong Meia, Hu Liaoa, Zhilan Xiaoa, Chenglin Guoa and Lunxu Liua,* a b
Department of Thoracic Surgery, West China Hospital, Sichuan University, Chengdu, China Department of Thoracic Surgery, Affiliated Hospital of Guizhou Medical University, Guiyang, China
* Corresponding author. No. 37, Guoxue Alley, Chengdu, Sichuan 610041, China. Tel: +86-28-85422494; fax: +86-28-85422494; e-mail: [email protected] (L. Liu). Received 28 January 2015; received in revised form 27 March 2015; accepted 8 April 2015
Abstract OBJECTIVES: Primary mediastinal myelolipoma (PMM) is a rare benign tumour composed of haematopoietic tissue and mature adipose tissue. Here, we report the largest series aiming to investigate the outcomes of surgical treatment for patients with PMM. METHODS: We retrospectively reviewed the data of 12 patients operated in a single institute during the period between April 2008 and December 2014. RESULTS: There were 7 female and 5 male patients between 54 and 73 years old (median age, 64 years). Among them, 11 patients underwent unilateral (n = 10) or bilateral (n = 1) mass resection via video-assisted thoracic surgery (VATS), and 1 patient underwent a planned open thoracotomy due to a large tumour volume. The VATS operating time ranged from 20 to 65 min (median, 30 min) and intraoperative blood loss ranged from 20 to 60 ml (median, 30 ml). The open thoracotomy operating time was 120 min, and the blood loss was 1000 ml; thus, the patient received blood transfusion (2 units of RBCs). No operative mortalities or major postoperative complications were observed. All patients experienced a regular follow-up ranging from 2 to 80 months with a median follow-up of 18 months. No recurrence was observed at the time of evaluation. CONCLUSIONS: Surgical treatment is recommended for the diagnosis and treatment of PMM, while VATS is a safe and feasible option in most cases. Keywords: Mediastinum • Myelolipoma • Video-assisted thoracic surgery • Thoracotomy • Prognosis
INTRODUCTION
MATERIALS AND METHODS
Myelolipoma is a rare mesenchymal tumour composed of an admixture of mature adipose tissue and bone marrow cells. This tumour was first discovered by Gierke in 1905 and named myelolipoma by Oberling in 1929 [1]. Henceforward, reports on myelolipoma gradually increased. Myelolipoma is often encountered in the adrenal gland, while the mediastinal location is extremely unusual. A primary mediastinal myelolipoma (PMM) is often asymptomatic and detected during routine X-ray or computed tomographic (CT) examination as incidentalomas. A review of the literature revealed that only some single case reports have been reported to date. To our knowledge, this study involves the largest series of surgically treated patients with PMM from a single institute. In this study, we summarize our knowledge in an attempt to present a surgical treatment strategy for PMM.
Patients There were 7 female and 5 male patients between 54 and 73 years old (median age, 64 years). Among them, 5 male patients were current smokers, and the rest were non-smokers. Most patients were referred to our hospital asymptomatically, while the other 4 patients were presented with cough, back pain or fever. Seven patients were presented with combined diseases. The demographic and clinical characteristics of these patients are listed in Table 1.
Preoperative assessment All of the patients received routine laboratory studies, respiratory function tests, electrocardiography, X-ray and CT of the thorax
© The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
ORIGINAL ARTICLE
ORIGINAL ARTICLE – THORACIC
Interactive CardioVascular and Thoracic Surgery (2015) 1–5 doi:10.1093/icvts/ivv112
F: female; M: male; RPM: right posterior mediastinum; LPM: left posterior mediastinum; BPM: bilateral posterior mediastinum; T-VATS: triportal video-assisted thoracic surgery; U-VATS: uniportal video-assisted thoracic surgery.
22 15 13 9 7 5 2 4.0 × 3.0 3.0 × 2.0 4.0 × 3.0 6.5 × 4.0 3.0 × 2.0 5.0 × 4.0 14 × 12 61 63 61 65 65 54 65 6 7 8 9 10 11 12
M M F F F F M
No Yes No No No No Yes
None Cough None None Fever None None
RPM LPM RPM RPM RPM LPM LPM
Myelolipoma Myelolipoma Myelolipoma Neurogenic tumour Pleural tumour Myelolipoma Teratoma
T-VATS T-VATS T-VATS T-VATS T-VATS T-VATS Thoracotomy
20 25 35 30 25 20 120
30 20 50 40 30 20 1000
No 21 RPM 67 5
F
No
None
Hypertension, diabetes, hypothyroidism Diabetes None Hypertension Diabetes None Anaemia None
Pheochromocytoma
U-VATS
20
100
No No No No 80 80 56 31 20 50 30 60 35 50 30 65 T-VATS T-VATS T-VATS T-VATS
2.5 × 2.0 4.0 × 3.0 5.0 × 4.0 7.0 × 5.5; 3.8 × 2.8 2.0 × 2.0 RPM RPM LPM BPM 71 73 63 54 1 2 3 4
F M M M
No Yes Yes Yes
None None Back pain Cough
Diabetes None Thrombopenia None
Pleural tumour Neurogenic tumour Neurogenic tumour Neurogenic tumour
Recurrence Follow-up (months) Blood loss (ml) Time of op (min) Operation Preoperative diagnosis Size (cm) Location Accompanied disease Symptoms Smoking Sex Age No.
Table 1: Clinical features of PMMs in the study
No No No No No No No
F. Lin et al. / Interactive CardioVascular and Thoracic Surgery
2
before operation. CT scans revealed unilateral or bilateral encapsulated, well-circumscribed posterior mediastinal tumour (Fig. 1). The CT density ranged from −60.0 to +10.0 Hounsfield units. All tumours had no calcification. The major axis of the tumours ranged from 2 to 14 cm (median, 4 cm). Eleven patients had a single mass (7 located in the right and 4 located in the left), and 1 patient had bilateral masses. Given the lack of distinct clinical and imaging characteristics, only 4 patients were diagnosed with PMMs preoperatively, whereas the other patients were diagnosed with neurogenic tumour, parietal pleura tumour, pheochromocytoma or teratoma, respectively. Informed consent for the operation was obtained from all the patients before surgery. Retrospective review of the medical records was approved by the Institutional Review Board (IRB) of West China Hospital.
Surgical procedures The operations were carried out under general anaesthesia with single-lung ventilation. The lateral decubitus position or semipronation (lateral decubitus position with 30° forerake) was used. The surgical approach [video-assisted thoracic surgery (VATS) or thoracotomy] was determined according to the size and local invasion of each tumour. The VATS procedure included triportal and uniportal access. The incisions of triportal VATS included a 1-cm thoracoscopic port on the middle axillary line in the seventh intercostal space (ICS) and two 1.5-cm incisions on the anterior axillary line in the fourth and eighth ICS, respectively. For a uniportal procedure, a 3-cm incision was made on the middle axillary line in the seventh ICS with the patient placed in a semiprone position. During the VATS procedure, the surgeon stood on the ventral side of the patient to perform the operation with endoscopic suction and an electric coagulation hook. During the process, endoscopic suction was used for manipulating the tumour and suctioning away the blood and smoke to provide a clear surgical field. In contrast, the surgeon stood at the back of the patient to perform open thoracotomy. The benign nature of each tumour was confirmed by an intraoperative frozen section. All postoperative diagnoses were verified pathologically.
RESULTS Detailed information of each patient is listed in Table 1. Eleven patients underwent unilateral (n = 10) or bilateral (n = 1) mass resection via VATS, while the remaining 1 patient underwent planned open thoracotomy due to the large tumour volume. Ten patients underwent triportal VATS procedures and 1 patient underwent a uniportal VATS procedure successfully (Video 1). Serious pleural adhesions were detected in 3 patients. One patient suffered intercostal artery injury. The VATS operating time ranged from 20 to 65 min (median, 30 min) and the intraoperative blood loss ranged from 20 to 60 ml (median, 30 ml). The open thoracotomy operating time was 120 min, and the blood loss was 1000 ml; thus, the patient received blood transfusion (2 units of RBCs). No operative mortalities or major postoperative complications were observed. Pathological confirmation was based on routine light microscopic sections stained by haematoxylin and eosin (H&E). The tumours were composed of adipose tissue and haematopoietic elements (Fig. 2). All the patients underwent a regular follow-up ranging from 2–80 months
3
ORIGINAL ARTICLE
F. Lin et al. / Interactive CardioVascular and Thoracic Surgery
Figure 1: (A–D) Chest CT scans of 4 patients revealed the different, well-circumscribed posterior mediastinal tumours with uneven density on the right or left side of the vertebrae, respectively (arrows).
Video 1: Uniportal VATS resection for a primary mediastinal myelolipoma in the right posterior mediastinum.
(median, 18 months). No recurrence has been observed at the time of evaluation.
DISCUSSION PMM is a rare benign tumour, which is composed of mature adipose tissue and haematopoietic elements, and it is more often located at the right posterior mediastinum. Most cases are asymptomatic and detected incidentally during regular physical examination just like our cases. Only a few patients may present with unspecific symptoms, such as back pain and cough. A review of
the literature [2–14] in Table 2 and the results of our cases revealed that PMMs were more frequently detected in the elderly. It is generally agreed upon that CT is the most common and useful method for the diagnosis of PMM. This tumour often presents as an encapsulated and well-circumscribed tumour consisting of fatty tissue density, mixed with haematopoietic tissue appearing as partial high-density areas on CT. If the boundary between the tumour and the adjacent vital organs, such as the aorta, oesophagus or intervertebral foramen, cannot be clearly identified, supplementary MRI can provide additional information regarding the nature and extent of the tumour, which is useful for surgeons to evaluate the resectability and design surgical procedures. No characteristic finding can lead to a preoperative diagnosis of PMM, which should be distinguished from other similar tumours, including neurogenic tumours, lymphomas, malignant mesotheliomas and extramedullary haematopoietic tissue. Among these tumours, the distinction between myelolipoma and extramedullary haematopoietic tumours is important. Histologically, myelolipoma is composed of abundant fat tissue and a small amount of normal haematopoietic element. In contrast, extramedullary haematopoietic tumours show markedly different characteristics with abnormal haematopoietic components, and erythroid hyperplasia is common. In addition, most patients with extramedullary haematopoietic tumours usually present with some primary blood system diseases, such as hereditary spherocytosis and mediterranean anaemia, which also play a role in the differential diagnosis of myelolipoma.
F. Lin et al. / Interactive CardioVascular and Thoracic Surgery
4
Figure 2: The tumour composed of mature adipose tissue and haematopoietic elements (H&E staining, A: ×100; B: ×200).
Table 2: Reported cases of PMMs in the past 20 years No.
Author [ref.]
Time
Age
Sex
Size (cm)
Number
Location
Treatment
Follow-up
1 2 3 4 5 6 7 8 9 10 11 12 13
Wyttenbach et al. [3] Minamiya et al. [4] Koizumi et al. [5] Kawanami et al. [6] Gao et al. [7] Franiel et al. [2] Mohan et al. [8] Rossi et al. [9] Vaziri et al. [10] Geng et al. [11] Ema et al. [12] Fonda et al. [13] Nakagawa et al. [14]
1994 1997 1999 2000 2002 2004 2006 2007 2008 2013 2013 2013 2014
53 59 55 72 59 65 46 73 56 68 68 64 79
M M M M M F M F M F M F M
8.0 × 6.0 × 6.0 6.5 × 5.3 × 3.5 w4.0 Not stated 3.0 × 2.0 w4.5; w6.5 w4.5 w7.0 20 × 15 × 10 3.1 × 10; 2.5 × 9.0 Not stated 1.4 × 2.5 × 3.0 7.5 × 4.5 × 3.0; 1.9 × 1.5 × 1.1; 4.0 × 3.4 × 1.5
Single Single Single Multiple Single Multiple Single Single Single Multiple Single Single Multiple
RMM RPM PM BPM RPM BPM RAM LPM RPM BPM RPM LPM BPM
Thoracotomy Thoracotomy VATS Needle biopsy Thoracotomy Thoracotomy Thoracotomy Thoracotomy Thoracotomy Thoracotomy VATS VATS VATS
Not stated No recurrence Alive Not stated Not stated Alive Alive Not stated Dead Alive Alive Alive Alive
F: female; M: male; RAM: right anterior mediastinum; RPM: right posterior mediastinum; RMM: right middle mediastinum; LPM: left posterior mediastinum; BPM: bilateral posterior of mediastinum; PM: posterior mediastinum; VATS: video-assisted thoracic surgery.
There is still controversy about the surgical indication of PMM. Kawanami et al. [6] proposed that if a definitive diagnosis was established through CT-guided needle biopsy, surgery was unnecessary for asymptomatic patient. Kenney et al. [15] proposed that such tumours should be resected if they have grown to more than 10 cm in diameter. Recently, surgeons have recognized the potential of progressive enlargement of the tumour, and that a delayed surgery may cause more trauma and risks, particularly in elderly patients. Hence, an increasing number of patients have received surgical therapy in the early stage and gained ideal outcomes [10–13]. Considering the risks of haemorrhage and pneumothorax, we propose that biopsy is unnecessary when surgery is deemed necessary. Thus, no patient underwent CT-guided biopsy preoperatively in our study. The minimally invasive VATS has become a widely accepted alternative for the resection of mediastinal tumours. However, there are only a few case reports about application of VATS for PMM due to the low morbidity. In this study, we presented the largest case series of PMM patients undergoing VATS resection successfully. Triportal VATS was the most commonly used procedure.
Compared with open thoracotomy, this minimally invasive procedure was related with many advantages, such as less trauma, faster recovery, etc. With the development of thoracoscopic instruments and techniques, we also attempted to apply uniportal VATS for one case. To facilitate the operation through only one access, the patient’s position was adjusted from lateral to semiprone. Thus, the posterior mediastinum was exposed better with the pulmonary lobes falling forwards. Under this condition, only three instruments were inserted into the thoracic cavity at the same time, which reduced mutual interference between different instruments. Our study presented a satisfactory clinical outcome including shorter operating time and less blood loss. Based on our own experience and reports in the literature, we proposed that most PMMs with size ≤8 cm can be successfully resected via VATS. During operations, we also noted that PMM was a tumour with rich blood supplies, which arose predominantly from the branches of the aorta or intercostal arteries. The main difficulty during resection of PMMs via VATS lies in how to safely divide these vessels. In 1 case, an intercostal artery was injured accidentally and caused bothersome bleeding. Fortunately, the bleeding
was stopped successfully via compression and electrocoagulation. In addition, pleural adhesions were common in cases with a largesized tumour, which also increased the difficulty of operation. In the open thoracotomy, the large tumour accompanied by severe adhesions resulted in excessive intraoperative bleeding; therefore, an open thoracotomy was more suitable for the resection of tumours of larger size.
CONCLUSIONS In conclusion, this is the largest case series demonstrating that VATS is safe and feasible for the surgical treatment of PMMs with satisfactory clinical outcomes. The less invasive technique of uniportal VATS is a promising alternative. Further studies are needed to better understand the features of PMM. Conflict of interest: none declared.
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ORIGINAL ARTICLE
F. Lin et al. / Interactive CardioVascular and Thoracic Surgery
