猫胸腺瘤的诊断和手术治疗

王帆

Diagnosis and surgical treatment of thymoma in the cat

猫胸腺瘤的诊断和手术治疗

 

作者：Angelou V.；Angelou V.；Psalla D.；Papazoglou L.G.

 

翻译：王帆

 

> Abstract

摘要

Thymoma is a rare neoplasm seen in aged cats that derives from thymic epithelial cells and is usually located in the cranial mediastinum. Clinical signs include dyspnoea, coughing, anorexia, lethargy or regurgitation. Feline thymoma may also be associated with myasthenia gravis or exfoliative dermatitis. Diagnosis of the tumour is based on diagnostic imaging. Ultrasonography provides information concerning the consistency of the mass. The extent and invasiveness of the mass can only be determined by computed tomography. Cytologic examination can also facilitate diagnosis where thymic epithelial cells and small lymphocytes dominate. Surgery is the treatment of choice for feline thymomas with favourable results. Thymomas are approached through a median sternotomy or intercostal thoracotomy. Definite diagnosis of thymoma can only be confirmed by histopathologic examination. The prognosis of feline thymoma is favourable, providing it is not associated with paraneoplastic syndromes or metastatic disease.

胸腺瘤是一种罕见的肿瘤，见于老年猫，起源于胸腺上皮细胞，通常位于前纵膈。临床症状包括呼吸困难、咳嗽、厌食、嗜睡或反流。猫胸腺瘤也可能与重症肌无力或表皮剥脱性皮肤病有关。肿瘤的诊断是基于诊断性影像检查。超声检查可提供有关肿块一致性的信息。肿块的范围和侵袭性只能通过计算机断层扫描来确定。细胞学检查也有助于诊断，见胸腺上皮细胞和小淋巴细胞为主。手术是治疗猫胸腺瘤的首选，效果良好。胸腺瘤可通过胸骨正中切开术或肋间开胸术进行。胸腺瘤的确切诊断只能通过组织病理学检查来证实。猫胸腺瘤的预后良好，只要它不伴有副肿瘤综合征或转移性疾病。

Key words

关键词

Cat；Exfoliative dermatitis；Myasthenia gravis；Thymectomy；Thymoma

猫；表皮剥脱性皮肤病；重症肌无力；胸腺切除术；胸腺瘤

 

> Incidence and epidemiology

> 发病率和流行病学

Thymoma is the most common thymic neoplasms that arises from thymic epithelial cells. Thymomas have been described in cattle, dogs, cats, sheep, goats, horses, pigs and rabbits. Thymoma and lymphoma represent the most common thymic neoplasms in cats.Feline thymoma is a rare neoplasm, usually benign and slowly progressive, localised in the cranial mediastinum. A cervical thymoma arising from an ectopic thymus has also been described. Cats with a median age of 10 years are usually affected. No breed predilection has been reported.

胸腺瘤是由胸腺上皮细胞引起的最常见的胸腺肿瘤。牛、犬、猫、绵羊、山羊、马、猪和兔子都有胸腺瘤。胸腺瘤和淋巴瘤是猫最常见的胸腺肿瘤。猫胸腺瘤是一种罕见的肿瘤，通常是良性的，进展缓慢，位于前纵膈。也描述过颈部胸腺瘤起源于异位胸腺。中位年龄为10岁的猫常患病。没有品种倾向性的报道。

 

> Clinical signs, physical and laboratory examination findings

> 临床症状、体格检查和实验室检查

Dyspnoea, coughing, anorexia, lethargy, vomiting and rarely regurgitation are common clinical signs; thymoma may also be diagnosed incidentally during routine clinical examination. All such signs are usually mild until the mass compresses the lungs, thereby provoking respiratory distress. Muffled heart sounds as well as poor compressibility in the cranial portion of thorax are also commonly detected. A few cats may develop signs associated with paraneoplastic syndromes including myasthenia gravis or exfoliative dermatitis. Cats with myasthenia gravis are presented with a history of neuromuscular weakness, walking difficulties, swallowing problems, hypersalivation, head tremor, dysphagia, ventroflexion of the neck or dysphonia. Diagnosis of myasthenia gravis is made by measurement of acetylocholine receptor antibody concentration. Cats with exfoliative dermatitis may present erythema of the pinnae, generalised twitching, obsessive grooming, pica, dermatitis over the pinnae, lateral thorax, abdomen, limbs, perineum and tail, generalized seborrhoea, epidermal erythema and exfoliation (Figure 1).

呼吸困难、咳嗽、厌食、嗜睡、呕吐和罕见反流是常见的临床症状。胸腺瘤也可能在常规临床检查中被偶然诊断出来。所有这些症状通常都很轻微，直到肿块压迫肺部，从而引起呼吸窘迫。心音低沉以及胸腔头部压缩性差也常被检测到。少数猫可能会出现与副肿瘤综合征相关的症状，包括重症肌无力或表皮剥脱性皮肤病。患有重症肌无力的猫有神经肌肉无力、行走困难、吞咽问题、流涎过多、头部震颤、吞咽困难、颈部腹屈或发音困难的病史。诊断重症肌无力是通过测量乙酰胆碱受体抗体浓度。患有表皮剥脱性皮肤病的猫可能会出现耳廓发红、全身性抽搐、强迫性理毛、异食癖、耳廓、胸外侧、腹部、四肢、会阴和尾部皮肤病、全身性皮脂溢、表皮发红和表皮剥脱(图1)。

 

 

Figure 1. Exfoliative dermatitis in a 4-year-old cat with thymoma.

图1：一只4岁胸腺瘤患猫的表皮剥脱性皮肤病

 

Complete blood count is usually unrewarding. Cats with thymoma may present eosinophilia, lymphocytosis, leukocytosis, mild-to-moderate anaemia and hyperproteinaemia. Biochemical abnormalities may include increased serum creatinine, blood urea nitrogen, plasma protein and creatinine kinase, hypercholesterolaemia, hyperglycaemia and rarely high alanine transaminase and alkaline phosphatase activity.

全血细胞计数通常是无异常。患有胸腺瘤的猫可表现为嗜酸性粒细胞增多、淋巴细胞增多、白细胞增多、轻度至中度贫血和高蛋白血症。生化异常可能包括血清肌酐、血尿素氮、血浆蛋白和肌酸激酶升高、高胆固醇血症、高血糖和罕见的高谷丙转氨酶和碱性磷酸酶。

 

> Diagnostic imaging

> 影像诊断

Radiography

X线 

The thymus is not visible on thoracic radiographs in normal cats due to its location and atrophy. Radiographs are very useful in diagnosing cranial mediastinal masses; the presence of a soft tissue opacity ventral to the trachea could be the thymus or cranial vena cava, branchionocephalic trunk, mediastinal lymph nodes and left subclavian artery, although it is not possible to distinguish among these structures. The presence of a soft tissue opacity in the ventral aspect of the cranial mediastinum compressing the cranial lung lobes and resulting in caudal displacement of the cardiac silhouette and dorsal displacement of the trachea or pleural effusion are commonly visualized in thoracic radiographs (Figures 2 a & b, 3 a & b). Aspiration pneumonia and megaesophagus are rarely seen.

正常猫胸腺由于其位置和萎缩，在胸部x线片上不可见。x线片在诊断前纵膈肿块时非常有用;气管腹侧的软组织密度升高可能是胸腺或前腔静脉、头臂支、纵隔淋巴结和左锁骨下动脉，但无法区分这些结构。胸部x线片常可见前纵膈腹侧软组织阴影压迫前肺叶，导致心脏轮廓尾侧移位、气管背侧移位或胸腔积液(图2a和b，图3a和b)。吸入性肺炎和巨食道少见。

 

 

Figure 2a. Cat of figure 1. Lateral thoracic radiograph showing a thymoma in the cranial mediastinum.

图2a：图1患猫。胸腔侧位X线片可见前纵膈的胸腺瘤。

Figure 2b. Ventrodorsal thoracic radiograph showing a thymoma in the cranial mediastinum.

图2b：腹背位胸腔X线片可见前纵膈的胸腺瘤。

 

Figure 3a. Lateral thoracic radiograph showing pleural fluid and a thymoma in the cranial mediastinum of a cat.

图3a：一只猫胸腔侧位X线片可见胸腔积液和前纵膈的胸腺瘤。

Figure 3b. Ventrodorsal thoracic radiograph showing a thymoma in the cranial mediastinum and pleural fluid accumulation.

图3b：腹背位胸腔X线片可见前纵膈的胸腺瘤和胸腔积液。

 

 

Ultrasonography

超声

Ultrasonography provides information concerning the consistency of the tumour. Fine needle aspiration (FNA) and biopsy of the tumour can be performed under ultrasound guidance. The tumour can be solid or cystic. Common findings associated with the presence of thymoma as seen on thoracic ultrasonography include zones of mixed echogenicity with hypoechoic and anechoic areas identified in the cranial and mid-thorax or hyperechoic areas associated with the presence of cholesterol crystals (Figure 4). Other findings include the presence of pleural effusion or cardiac tamponade.

超声检查提供有关肿瘤一致性的信息。可在超声引导下进行细针穿刺抽吸(FNA)和肿瘤活检。肿瘤可以是实性或囊性的。胸腺瘤在胸部超声检查中常见的表现包括头侧和胸部中部低回声区和无回声区混合回声区，或与胆固醇晶体存在相关的高回声区(图4)。其他表现包括胸膜积液或心脏填塞。

 

 

Figure 4. Cat of figure 1. Thoracic ultrasound revealed a mild hypoechoic compared to surrounding tissue and well-defined mass (m) located just cranial to the heart (h).

图4：图1患猫。胸腔超声可见对比度轻度低于周围组织，以及位于心脏头侧的边界清晰的肿物（m）。

 

Computed Tomography

CT

Computed tomography (CT) provides further information on the invasiveness of thymoma compared to plain radiography and ultrasound and has increased sensitivity but decreased specificity. Compression of the cranial vena cava, displacement of subclavian vessels, trachea or heart can be seen (Figure 5). Metastatic pulmonary nodules and lymph node enlargement can also be identified.

与x线平片和超声相比，计算机断层扫描(CT)提供了胸腺瘤侵袭性的进一步信息，敏感性增加，但特异性降低。可见前腔静脉受压，锁骨下血管、气管或心脏移位(图5)。也可见转移性肺结节和淋巴结肿大。

 

 

Figure 5. A contrast–enhanced CT scan of a feline thorax showing a large thymoma displacing the heart to the right side (courtesy Dr Susanne Boroffka Utrecht University).

图5：一只猫的胸腔增强CT检查，可见一个大的胸腺瘤将心脏右侧移位。

 

Biologic behavioUr

生物学行为

Thymomas do not usually metastasize. Local spread to the lungs and lymph nodes has been reported but distant metastases are rare.

胸腺瘤通常不转移。有局部扩散到肺和淋巴结的报道，但罕见远端转移。

 

> Cytologic examination

> 细胞学检查

Fine needle aspiration of thymoma performed under ultrasound guidance and cytologic examination of the aspirate may be diagnostic for thymoma, although it is sometimes hard to distinguish thymoma from lymphoma.Not uncommonly, negative or unrewarding results can be reported. On cytologic evaluation of thymomas, two types of cells dominate: thymic epithelial cells and small lymphocytes that exceed 80% and can be seen as single cells or within sheets. A mixed population of cells including mast cells, neutrophils, mononuclear cells, eosinophils, small lymphocytes and occasional lymphoblasts and erythrocytes may also be observed. The epithelial cells are polygonal, spindle or cuboidal with round to oval or reniform nuclei. The cytoplasm is usually lightly eosinophilic. Nucleoli are rarely seen, even though in some cases they can be large and prominent. The majority of lymphocytes are small, but medium and large lymphocytes may also be noted. A sterile, cholesterol-rich exudate obtained from a cyst located in the central of the tumour has been reported. Fluid aspirated from the thoracic cavity is milky containing small mature lymphocytes. In general, the cytologic examination does not always establish a diagnosis, but it is useful as a quick, initial screening examination.

在超声引导下对胸腺瘤进行细针穿刺抽吸并对抽吸物进行细胞学检查可以诊断胸腺瘤，但有时很难将胸腺瘤与淋巴瘤区分开来。通常情况下，会有阴性和无异常结果。在胸腺瘤的细胞学评估中，两种类型的细胞占主导地位:胸腺上皮细胞和小淋巴细胞，超过80%，可见单个细胞或细胞成片。还可观察到肥大细胞、中性粒细胞、单个核细胞、嗜酸性粒细胞、小淋巴细胞和偶见淋巴母细胞和红细胞等混合细胞群。上皮细胞呈多角形、梭形或立方形，核为圆形至椭圆形或肾形。细胞质通常是轻度嗜酸性的。罕见核仁，但有些病例中核仁可能很大很明显。淋巴细胞多为小淋巴细胞，也可见中、大淋巴细胞。有报道从位于肿瘤中心的囊肿中可能含有无菌、富含胆固醇的渗出物。胸腔吸出的液体呈乳白色，含有成熟的小淋巴细胞。一般来说，细胞学检查并不总是能得到诊断，但它是有用的快速，初步筛查检查。

 

> Ancillary testing

> 特殊检查

Cats suspected for myasthenia gravis should undergo a few additional tests including electromyography, measurement of nerve conduction velocity and repetitive nerve stimulation at rates up to 30 stimuli/s. Muscle biopsy can also be obtained. However, definite diagnosis is made by measurement of acetylcholine receptor antibodies.In cats with exfoliative dermatitis, additional tests include skin scrapings to exclude the presence of ectoparasites or dermatophytes, tape strippings or ear canal mineral oil wash-outs. Skin biopsies are also obtained, which usually show orthokeratotic and parakeratotic hyperkeratosis, epidermal hyperplasia and inflammatory infiltration of the superficial and mid-dermis by lymphocytes, neutrophils and possible mast cells.

被怀疑患有重症肌无力的猫应进行其他检查，包括肌电图、神经传导速度的测量和频率高达30次/秒的重复神经刺激。也可以进行肌肉活检。然而，确诊是通过测量乙酰胆碱受体抗体。对于患有表皮剥脱性皮肤病的猫，其他检查包括皮肤刮片以排除外寄生虫或皮肤癣菌的存在，胶带粘贴或耳道分泌物镜检。皮肤活检通常显示正角化和角化不全性角化过度，表皮层增生，真皮浅层和中层淋巴细胞、中性粒细胞和可能的肥大细胞炎性浸润。

 

> Differential diagnosis

> 鉴别诊断

A list of differentials for feline thymic conditions is presented in table 1. However, the most common masses found in the cranial mediastinum are lymphoma and thymoma; it is important to distinguish between them because of the different treatment required. While in thymoma the treatment is surgical, in lymphoma it is medical. Thymoma is frequent in older cats; it shows slower progress than lymphoma and a better prognosis because it responds well to surgical excision. On cytology, a mixture of lymphoid and thymic epithelial cells are detected in thymomas, while neoplastic lymphoblasts are detected in lymphomas. However, cytologic examination is often misleading and the only way to establish a definite diagnosis of thymoma is by histologic evaluation. A list of differentials in cats with skin disease associated with thymoma is provided in Table 2. Definite diagnosis is based on history, physical examination and skin histopathology.

表1列出了猫胸腺疾病的鉴别诊断列表。然而，在前纵膈最常见的肿块是淋巴瘤和胸腺瘤。区分它们很重要，因为需要不同的治疗方法。胸腺瘤的治疗方法是手术，而淋巴瘤则是药物治疗。胸腺瘤常见于老年猫，它表现出比淋巴瘤更慢的进展和更好的预后，因为它对手术切除反应良好。在细胞学上，在胸腺瘤中检测到淋巴样和胸腺上皮细胞的混合，而在淋巴瘤中检测到肿瘤淋巴母细胞。然而，细胞学检查往往容易误导，建立明确诊断胸腺瘤的唯一方法是通过组织学评估。表2列出了患有与胸腺瘤相关的皮肤病的猫的鉴别诊断列表。明确诊断是根据病史、体格检查和皮肤组织病理学检查。

 

 

Table 1. Differential diagnosis of thymic conditions in cats

表1：猫胸腺疾病鉴别诊断

胸腺淋巴瘤

胸腺瘤

胸腺鳃裂囊肿

胸腺增生

胸腺发育不全

胸腺出血

胸腺淀粉样变性

胸腺脂肪瘤

 

 

Table 2. Differential diagnosis of cats with skin disease associated with thymoma

表2：猫胸腺瘤相关皮肤病的鉴别诊断

皮肤癣菌病

马拉色皮肤病

皮肤超敏反应

落叶型天疱疮

药物副反应

胰腺癌或肝胆腺癌相关脱毛

趋上皮淋巴瘤

皮脂腺炎

系统性红斑狼疮

蠕形螨病

姬螯螨病

 

 

> Surgical treatment

> 手术治疗

Treatment of thymomas includes surgical excision, chemotherapy or radiation. Surgical excision of thymomas or thymectomy is the treatment of choice for most thymomas. Thoracic exploration is also recommended to evaluate the invasiveness of thymoma. Generally, thymomas are commonly removed via median sternotomy, although in some cases excision is performed via lateral thoracotomy (Figure 6). The tumour may also be an incidental finding on exploratory thoracotomy. Median sternotomy is preferable for large tumours since it allows access to the entire thoracic cavity (Figure 7). Connective tissue is frequently adhered to the sternum and electrocautery is recommended for transection to allow visualization of the thymus. An initial visual inspection of the pericardium, blood vessels including cranial vena cava and internal thoracic arteries and pleura is recommended to determine the degree of invasion of the mass into the surrounding tissues prior to dissection.Vascular invasion can also be evaluated preoperatively using ultrasonography and CT imaging, even though the extent of the mass cannot always be estimated until palpation and visual inspection is effected at the time of surgery. The mass is removed with a sharp and blunt dissection. If the mass has extended to the pericardium, a pericardectomy should be performed. It is also important to isolate a single side of the mass. If the cranial or caudal sides of the mass can be resected free from the surrounding tissue, the thymoma can be mobilized more easily rendering it easier to visualize the heart and the large vessels. If the cranial border of the mass can be dissected free from the cranial vena cava, the dissection can be performed more safely so as to avoid laceration of this vein. The phrenic nerves should be identified within the tumour or surrounding tissues and be preserved.

胸腺瘤的治疗包括手术切除、化疗或放疗。手术切除胸腺瘤或胸腺切除术是大多数胸腺瘤的治疗选择。胸廓探查也被推荐用于评估胸腺瘤的侵袭性。一般来说，胸腺瘤通常通过胸骨正中切开术切除，但在某些情病例中，则通过胸侧切开术进行切除(图6)。肿瘤也可能是在开胸探查手术中偶然发现。对于较大的肿瘤，胸骨正中切开术是可取的，因为它可以接触到整个胸腔(图7)。结缔组织经常粘附在胸骨上，建议电灼横切面以显示胸腺。建议在剥离前对心包、包括前腔静脉、胸内动脉和胸膜在内的血管进行初步观察，以确定肿块对周围组织的侵袭程度。血管侵袭也可以在术前使用超声和CT成像进行评估，但在手术时进行触诊和观察之前，肿块的范围并不总是能被评估出来。用尖锐钝性剥离术切除肿块。如果肿块已延伸到心包，则应进行心包切除术。同样重要的是分离出单侧肿物。如果肿块的颅侧或尾侧可以从周围组织中自由切除，胸腺瘤可以更容易地分离，从而更容易看到心脏和大血管。如果肿块的颅缘能脱离前腔静脉进行剥离，则可以更安全地进行摘除，避免该静脉撕裂伤。膈神经应在肿瘤或周围组织内确定并保存。

 

 

Figure 6. Cat of figure 4. A thymoma as seen through a median sternotomy

图6：图4患猫。通过胸骨正中切开术可见一个胸腺瘤。

 

Figure 7. A large thymoma in a 10-year-old Siamese following a median sternotomy

图7：一只10岁暹罗猫，胸骨正中切开术可见一个大的胸腺瘤。

 

Lateral thoracotomy at the 5th or 6th intercostal space is preferable for smaller tumours (Figures 8 and 9). If it is not known preoperatively which side is more affected, a left lateral approach is preferred.

对于较小的肿瘤，首选在第5或第6肋间隙进行胸侧开胸术(图8和图9)。如果术前不知道哪一侧患病更大，则首选左侧入路。

 

 

 

Figure 8. A thymoma of the cat of figure 1 adhering to the pericardium is removed via a left lateral thoracotomy.

图8：图1患猫的胸腺瘤粘附在心包上，经左侧开胸术切除。

 

 

Figure 9. Cat of figure 1. The tumour following removal.

图9：图1患猫。切除后额肿瘤。

 

Before thoracotomy closure, a throracostomy tube is placed for the treatment of pneumothorax, and possible pleural effusion and haemorrhage is monitored.

在关闭胸腔前，放置胸导管治疗气胸，并监测可能的胸腔积液和出血。

 

Postoperatively, cats are hospitalized for three to seven days. The thoracostomy tube is usually removed 36 hours after surgery. During hospitalization, cats are given analgesic drugs including bupivacaine (1-2 mg/kg through the thoracostomy tube), meloxicam (0.05 mg.kg SID po), fentanyl (2-6 μg/kg/h as a constant rate infusion) and antibiotics. The follow-up includes physical examination and thoracic radiographs every 3-6 months to detect potential tumour recurrence.

术后，猫需要住院3到7天。胸导管通常在术后36小时取出。在住院期间，患猫使用镇痛药物，包括布比卡因(通过胸导管1-2 mg/kg)、美洛昔康(0.05 mg/kg，每日一次，po)、芬太尼(恒速输注2-6 μg/kg/h)和抗生素。随访包括每3-6个月进行一次体格检查和胸片检查，以发现潜在的肿瘤复发。

 

> Postoperative complications

> 术后并发症

Postoperative complications of thymectomy include anorexia, lethargy, corneal ulcers, intrathoracic haemorrhage, pyogranulomatous pleuritis associated with fungal hyphae and laryngeal paralysis. Myasthenia gravis has also been reported post thymectomy one to seven weeks after surgery.

胸腺切除术的术后并发症包括厌食、嗜睡、角膜溃疡、胸内出血、真菌菌丝相关的脓性肉芽肿性胸膜炎和喉麻痹。也有报道胸腺切除术后1至7周出现重症肌无力。

 

> Adjuvant treatment

> 辅助治疗

The routine use of adjuvant chemotherapy is not justified in cats. Radiation therapy has occasionally been used alone or combined with surgery with promising results.

在猫上常规使用辅助化疗是不合理的。放射治疗偶尔单独使用，或与手术联合使用，效果很好。

 

Treatment of myasthenia gravis includes the use of anticholinesterase drugs such as pyridostigmine bromide (0.5 mg/kg BID-TID po) and neostigmine alone (0.04 mg/kg/6 h im) or combined with prednisone (1.5-2 mg/kg BID po). In cats with myasthenia gravis associated with thymoma, thymectomy is considered as a useful treatment adjunct to immunosuppressive therapy. In a few cats, clinical signs of myasthenia gravis resolve following thymectomy.

重症肌无力的治疗包括使用抗胆碱酯酶药物，如溴化吡多斯的明(0.5 mg/kg BID- tid ，po)和单独使用新斯的明(0.04 mg/kg/6 h im)或联合泼尼松龙(1.5-2 mg/kg BID po)。在伴有胸腺瘤的重症肌无力的猫中，胸腺切除术被认为是免疫抑制治疗的有效辅助治疗。在少数猫中，重症肌无力的临床症状在胸腺切除术后消失。

 

> Histopathologic findings

> 组织病理学检查

histopathologic examination show thymomas to consist of a mixture of cells including thymic epithelial cells which can be round, oval or spindle in shape as well as small lymphocytes (Figure 10). The nuclei of epithelial cells can be round to oval with eosinophilic or clear cytoplasm and nucleoli are not frequently observed. The proportion of epithelial cells to lymphocytes varies in thymomas or even in areas of the same neoplasm.In two reported cases, the proportion of lymphoid and epithelial cells was similar. Mitotic figures are not frequent.Foci of haemosiderosis, necrosis, mineralization, oedema and gland formation may also be observed. A large proportion of thymomas are cystic. In humans, the criteria for classification of cystic thymomas include a) the presence of solid expanses consisting of a dual population of epithelial cells and small mature lymphocytes within the cyst walls, b) perivascular spaces and areas of medullary differentiation, and c) the absence of epithelial lining. Cystic thymomas have also been described in cats. The cysts are lined by flattened epithelial cells and small lymphocytes, which create a cell layer. Cysts may contain red blood cells and stainable fluid; Hassal’s corpuscles may occasionally be observed. Clear cell thymoma where neoplastic cells emerge as large clear cells comprising a uniform mass has been reported. Mast cells may also be present. Amyloid deposition has also been reported. Areas of necrosis and cystic cavities may be detected too. Additional tests that can be used for the characterization of thymoma include flow cytometry, immunocyto(histo)chemistry and electron microscopy.

组织病理学检查显示胸腺瘤由多种细胞组成，包括圆形、椭圆形或梭形胸腺上皮细胞以及小淋巴细胞(图10)。上皮细胞的细胞核可呈圆形或卵圆形，胞浆嗜酸性或透明，核仁不常见。在胸腺瘤中，上皮细胞与淋巴细胞的比例不同，甚至在同一肿瘤区域也不相同。在两个报告的病例中，淋巴细胞和上皮细胞的比例相似。有丝分裂不常见。也可观察到血铁沉着、坏死、矿化、水肿和腺体形成的病灶。胸腺瘤很大一部分是囊性的。在人类中，囊性胸腺瘤的分类标准包括:a)囊肿壁内存在由上皮细胞和成熟小淋巴细胞组成的实质性扩张，b)血管周围间隙和髓质分化区，c)无内衬上皮细胞。囊性胸腺瘤在猫上也有报道。囊肿内排列着扁平的上皮细胞和小淋巴细胞，形成一个细胞层。囊肿可能含有红细胞和着染液体。偶尔可以观察到哈萨尔小体。已报道透明细胞胸腺瘤的肿瘤细胞出现为大透明细胞，包括一个均匀的肿块。肥大细胞也可能存在。淀粉样蛋白沉积也有报道。也可见坏死区域和囊腔。可用于胸腺瘤特征的其他检测包括流式细胞术、免疫细胞(组织)化学和电子显微镜。

 

 

Figure 10. Thymoma (Female, DSH, adult cat). Thymic architecture is obscured due to the neoplastic proliferation of epithelial cells. A limited proportion of small lymphocyte is also seen. Haematoxylin-eosin, magnification x 200 objective lens.

图10。胸腺瘤(雌性，DSH，成年猫)。由于上皮细胞的肿瘤增生，胸腺结构模糊。也可见占比有限的小淋巴细胞。苏木精-伊红，放大200倍物镜。

 

> Staging

> 分期

Clinical staging of a thymoma is based on a) tumour invasion into the capsule and surrounding tissues on CT scans, b) intraoperative findings concerning tumour distinctive delineation from surrounding structures including mediastinal pleura, lymph nodes, pericardium and vena cava, c) the presence or absence of neoplastic cells in surgical margins as seen microscopically, and d) metastatic disease.This staging system may be used to recommend medical management and define prognosis in cats with thymoma.The staging system is shown in Table 3.

胸腺瘤的临床分期是基于以下几个方面:a) CT扫描显示肿瘤侵入包膜和周围组织;b)术中发现肿瘤与周围结构(包括纵隔胸膜、淋巴结、心包和腔静脉)有明显区分边界;c)显微镜下观察手术边缘是否有肿瘤细胞;d)转移性疾病。该分期系统可用于推荐胸腺瘤的医疗管理和确定预后。分段系统如表3所示。

 

 

TABLE 3. Criteria of Clinical Stages

表3：临床分期标准

Stage I:Macroscopically completely encapsulated and microscopically no capsular invasion I期：观察有完整包囊和镜检无侵袭

Stage II:1. Macroscopic invasion into surrounding fatty tissue or mediastinal pleura, or 2. Microscopic invasion into capsule II期：1：观察向周围脂肪组织或纵膈胸膜侵袭，或       2：镜检向包膜侵袭

Stage III：Macroscopic invasion into neighboring organ, i.e., pericardium, great vessels, or lung III期：观察向邻近器官侵袭，例：心包、大血管或肺

Stage IVa:Pleural or pericardial dissemination IVa期：胸膜或心包扩散

Stage IVb:Lymphogenous or hematogenous metastasis IVb期：淋巴或血液转移

 

> Prognosis

> 预后

The prognosis of feline thymomas that are non-invasive, non-metastatic and amenable to complete surgical excision is favourable.On the other hand, feline thymomas associated with paraneoplastic syndromes that cannot be controlled have a more guarded prognosis.

猫胸腺瘤的预后是非侵入性的，非转移性的，可达到完全手术切除。另一方面，猫胸腺瘤伴有无法控制的副肿瘤综合征，预后更谨慎。

 

However, in a few cases with myasthenia gravis and exfoliative dermatitis, the syndrome resolved following a thymectomy. The main prognostic factors associated with survival are shown in Table 4.Median survival for cats treated with thymectomy was reported to be 41 months.

然而，在少数有重症肌无力和表皮剥脱性皮肤病的病例中，该综合征在胸腺切除术后得到恢复。与生存相关的主要预后因素见表4。据报道，接受胸腺切除术的猫的中位生存期为41个月。

 

 

Table 4. Prognostic indicators for feline thymoma

表4：猫胸腺瘤预后指标

年龄

肿瘤侵袭性

组织病理学检查中的有丝分裂区域

肿物的淋巴细胞占比

 

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