Intrathoracic Tumors: Current Status and Classification

Dong-Seok Lee, Raja Flores

Abstract

Thoracic oncology encompasses a large spectrum of diseases. Between the various anatomic spaces and the different organ systems, there are a large variety of benign and malignant tumors that can develop within the chest. This chapter will focus primarily on the surgical management of the most commonly encountered thoracic malignancies.

Keywords

common thoracic malignancies; surgical management; lung cancer; esophageal cancer; mesothelioma; thymoma

Introduction

General Diagnostic Principles

Aside from a thorough history and examination, certain radiographic studies are essential tools for the thoracic surgeon. A standard chest x-ray provides a good overview—it can show larger lesions and may even show sequelae of smaller lesions such as effusions or postobstructive atelectasis. Different projections can offer additional information. Computed tomography (CT) enables visualization of smaller lesions and helps determine size, location, depth, and relation to other structures. Magnetic resonance imaging (MRI) is limited to assessing neural involvement or differentiating mediastinal structures; it does not usually offer more information than a CT. It is more often used for the evaluation of brain metastases. Positron emission tomography (PET) has become the standard for staging thoracic malignancies because it is more accurate than conventional imaging in detecting metastatic disease.¹

Lung Cancer

Tumors within the lung parenchyma may arise from primary lung etiologies or because of metastatic disease. The focus of this section will remain on primary lung cancers, for which nonsmall cell and small cell cancers account for over 90%. Smoking remains the single most important risk factor for the development of lung cancer, increasing risk 20-fold compared with nonsmokers. Other risk factors include radiation, other environmental toxins, and pulmonary fibrosis that have synergistic effects.²

Most patients are asymptomatic and develop symptoms once locally advanced or metastatic disease is present. Typicalsymptoms can include cough, hemoptysis, chest pain, or dyspnea. Involvement of local structures can result in specific symptoms, such as hoarseness (because of recurrent laryngeal nerve invasion), superior vena cava (SVC) syndrome (facial and upper extremity swelling because of SVC obstruction), and Pancoast syndrome (shoulder pain and Horner syndrome because of superior sulcus tumor invasion).

CT imaging has revolutionized the detection of lung cancer, allowing the discovery of smaller tumors and, consequently, enabling the treatment of earlier stage disease. The International Early Lung Cancer Action Program showed that 85% of patients diagnosed with lung cancer during screening were clinical stage I disease, and that those patients who underwent surgical resection within 1 month of diagnosis had an estimated 10-year survival of 92%.³ As a result, lung cancer screening has been deemed essential in the diagnosis and treatment of lung cancers such that it is recommended for patients aged 55 to 80 years with a 30-pack-year smoking history by the U.S. Preventive Services Task Force.

Diagnosis can only be confirmed with a tissue biopsy. Surgical biopsy has historically been performed, but, in more recent times, an initial biopsy is performed less invasively with a needle via either a transbronchial or transthoracic approach. Once a malignant diagnosis is obtained, decision on appropriate therapy is driven by the clinical stage. Lung cancer staging is based on the tumor node metastasis (TNM) classification (Table 4.1). In addition to PET imaging and MRI when clinically indicated to evaluate the presence of tumor spread, mediastinal staging may be necessary. This has classically been achieved with mediastinoscopy, but endobronchial ultrasound has seen increased utilization because of its less invasiveness and its ability to assess N1 nodes as well.

Table 4.1

Lung Cancer Staging Tumor Node Metastasis Classification (8th Edition)
4.1A
T/N/M Classification
T (Primary Tumor)
T0	No primary tumor
Tis	Carcinoma in situ (squamous or adenocarcinoma)
T1	Tumor ≤3 cm
T1mi	Minimally invasive adenocarcinoma
T1a	Superficial spreading tumor in central airways^a
T1a	Tumor ≤1 cm
T1b	Tumor >1 but ≤2 cm
T1c	Tumor >2 but ≤3 cm
T2	Tumor >3 but ≤5 cm or tumor involving: visceral pleura,^b main bronchus (not carina), atelectasis to hilum^b
T2a	Tumor >3 but ≤4 cm
T2b	Tumor >4 but ≤5 cm
T3	Tumor >5 but ≤7 cm or invading chest wall, pericardium, phrenic nerve; or separate tumor nodule(s) in the same lobe
T4	Tumor >7 cm or tumor invading: mediastinum, diaphragm, heart, great vessels, recurrent laryngeal nerve, carina, trachea, esophagus, spine; or tumor nodule(s) in a different ipsilateral lobe
N (Regional Lymph Nodes)
N0	No regional node metastasis
N1	Metastasis in ipsilateral pulmonary or hilar nodes
N2	Metastasis in ipsilateral mediastinal or subcarinal nodes
N3	Metastasis in contralateral mediastinal, hilar, or supraclavicular nodes
M (Distant Metastasis)
M0	No distant metastasis
M1a	Malignant pleural or pericardial effusion‡ or pleural or pericardial nodules or separate tumor nodule(s) in a contralateral lobe
M1b	Single extrathoracic metastasis
M1c	Multiple extrathoracic metastases (1 or >1 organ)
4.1B
Subcategories
T/M	Subcategory	N0	N1	N2	N3
T1	T1a	IA1	IIB	IIIA	IIIB
	T1b	IA2	IIB	IIIA	IIIB
	T1c	IA3	IIB	IIIA	IIIB
T2	T2a	IB	IIB	IIIA	IIIB
	T2b	IIA	IIB	IIIA	IIIB
T3	T3	IIB	IIIA	IIIB	IIIC
T4	T4	IIIA	IIIA	IIIB	IIIC
M1	M1a	IVA	IVA	IVA	IVA
	M1b	IVA	IVA	IVA	IVA
	M1c	IVB	IVB	IVB	IVB

^aSuperficial spreading tumor of any size but confined to the tracheal or bronchial wall. ^‡Atelectasis or obstructive pneumonitis extending to hilum; such tumors are classified as T2a if >3 and ≤4 cm, T2b if >4 and ≤5 cm.

^b Pleural effusions are excluded that are cytologically negative, nonbloody, transudative, and clinically judged not to be because of cancer.

From Detterbeck FC. The eighth edition TNM stage classification for lung cancer: what does it mean on main street? J Thorac Cardiovasc Surg. 2018;155(1):356–359.

Surgery offers the best chance for cure in patients with resectable nonsmall cell lung cancer. For patients who are not surgical candidates or who refuse surgery, local therapy such as stereotactic body radiation therapy can be offered. It is important to differentiate between operability and resectability. Operability refers to the patient’s comorbidities and ability to undergo surgery. Resectability refers to the extent of parenchymal resection required and the patient’s ability to tolerate it in light of their pulmonary functional status. For example, the patient may have a relatively small cancer centrally located such that a pneumonectomy would be required, but the patient would only be able to tolerate a lobectomy.

Clinical stage 1 and stage 2 cancers should proceed directly to surgery. Stage 3 cancers encompass a wide spectrum. N3 disease stage 3 cancers are not surgical candidates. A multidisciplinary approach is the best strategy for non-N3 disease stage 3 cancers and treatment can range from prompt surgery to induction therapy, followed by surgery to definitive chemotherapy with or without radiation therapy. Induction therapy may consist of either chemotherapy alone or chemoradiation therapy and is usually determined by institutional or surgeon practices. There are currently investigations in the role of immunotherapy into the neoadjuvant setting. Pembrolizumab (KEYTRUDA) recently approved by the FDA, is a sample of a drug that presumably stimulates the immune system to attack the cancer cells. Stage 4 cancers are referred for systemic therapy, and surgery is reserved for palliation of symptoms.

Once the decision to proceed with surgery has been made, the extent of resection and surgical approach must be considered. Lobectomy has been considered the gold standard technique for resection. The Lung Cancer Study Group reported increased locoregional recurrence rate and a trend toward decreased survival with limited resection versus lobectomy in 1995 ⁴ (Fig. 4.1). However, with the advent of lung cancer screening and the discovery of smaller cancers, this is being challenged, as more recent studies suggest no significant differences in recurrence rates and overall survival.⁵ The authors consider performing a sublobar resections in patients with small (<2 cm), anatomically feasible cancers with low standardized uptake value (Fig. 4.2). Extended resections may be required in the setting of locally advanced disease, such as chest wall invasion (Fig. 4.3) or invasion of the great vessels.

• Fig. 4.1 A 70-year-old male with 3-cm left upper lobe mass. He underwent left upper lobectomy. Pathology was a 4-cm T2aN0 adenosquamous carcinoma.

• Fig. 4.2 A 37-year-old male with a 2-cm right upper lobe mass. He underwent video-assisted thoracoscopic surgery right upper lobe posterior segmentectomy. Pathology was a 1.7-cm pT1bN0 adenocarcinoma.

• Fig. 4.3 A CT scan of a 73 years-old male (left) with hypermetabolic 4.2 cm right upper lobe on PET scan (right). Chest wall invasion was noted, and he underwent right upper lobectomy with chest wall resection and reconstruction. Pathology was a 7-cm T3N0 pleomorphic carcinoma.

Thoracotomy is the standard approach for lung resection. However, minimally invasive techniques such as video-assisted thoracoscopic surgery (VATS) and robotic surgery are increasingly being used. Minimally invasive surgery offers short-term benefits, such as less pain, shorter hospital stays, and fewer complications.⁶^,⁷ VATS also appears to offer improved long-term outcomes.⁸

Morbidity after lung cancer surgery is approximately 35%,⁹^,¹⁰ with the risk of major adverse events 9.1%.¹¹ Cardiac and pulmonary events are the predominant complications seen. Several risk models have been developed to try to predict perioperative risk for patients.¹² Perioperative mortality is 1.5% to 2.5%.

Esophageal Cancer

Esophageal cancer is the most common primary esophageal malignancy. Squamous cell carcinoma is more prevalent worldwide, with its strong association with smoking and alcohol, but adenocarcinoma is more common in the United States, with the rise of obesity, gastroesophageal reflux disease, and Barrett metaplasia. Because the esophagus traverses through three anatomic domains—the neck, chest, and abdomen—determining the location of the cancer is essential in guiding treatment. Cervical esophageal cancers are primarily treated with chemotherapy and radiation. Middle and lower esophageal cancers are offered multimodality therapy consisting of surgery, chemotherapy, and radiation.

Patients commonly present with dysphagia and weight loss. Diagnosis is obtained with endoscopy. Direct visualization provides information, such as size and location of the mass, and tissue diagnosis is obtained with biopsy forceps. Once the diagnosis is confirmed, clinical stage must be determined (Table 4.2). In esophageal cancer, depth of radial invasion is more important than size in staging. Therefore determining T and N staging is best achieved with endoscopic ultrasound (EUS). Tissue biopsy via ultrasound-guided fine needle aspiration (FNA) can also be performed on suspicious lymph nodes. EUS and EUS-FNA have high sensitivity and specificity in accurately diagnosing T stage and N stage, respectively.¹³ However, T2 lesions remain notoriously challenging with an accuracy of approximately 30% because both tumor upstaging and downstaging can occur¹⁴ (Fig. 4.4). Bronchoscopy may be necessary to rule out airway invasion.

Table 4.2

Esophageal Cancer Staging TNM Classification (8th Edition)
4.2A
Category	Criteria
T category
TX	Tumor cannot be assessed
T0	No evidence of primary tumor
Tis	High-grade dysplasia, defined as malignant cells confined by the basement membrane
T1	Tumor invades the lamina propria, muscularis mucosae, or submucosa
T1a^a	Tumor invades the lamina propria or muscularis mucosae
T1b^a	Tumor invades the submucosa
T2	Tumor invades the muscularis propria
T3	Tumor invades adventitia
T4	Tumor invades adjacent structures
T4a^a	Tumor invades the pleura, pericardium, azygos vein, diaphragm, or peritoneum
T4b^a	Tumor invades other adjacent structures, such as aorta, vertebral body, or trachea
N category
NX	Regional lymph nodes cannot be assessed
N0	No regional lymph node metastasis
N1	Metastasis in 1–2 regional lymph nodes
N2	Metastasis in 3–6 regional lymph nodes
N3	Metastasis in 7 or more regional lymph nodes
M category
M0	No distant metastasis
M1	Distant metastasis
Adenocarcinoma G Category
GX	Differentiation cannot be assessed
G1	Well differentiated, >95% of tumor is composed of well-formed glands
G2	Moderately differentiated, 50% to 95% of tumor shows gland formation
G3^b	Poorly differentiated. Tumors composed of nest and sheets of cells with <50% of tumor demonstrating glandular formation.
Squamous cell carcinoma G category
GX	Differentiation cannot be assessed
G1	Well differentiated. Prominent keratinization with pearl formation and a minor component of nonkeratinizing basal-like cells. Tumor cells are arranged in sheets, and mitotic counts are low.
G2	Moderately differentiated. Variable histologic features, ranging from parakeratotic to poorly keratinizing lesions. In general, pearl formation is absent.
G3^c	Poorly differentiated. Consist predominantly of basal-like cells forming large and small nests with frequent central necrosis. The nests consist of sheets or pavement-like arrangements of tumor cells, and occasionally are punctuated by small numbers of parakeratotic or keratinizing cells.
Squamous cell carcinoma L category^d
LX	Location unknown
Upper	Cervical esophagus to lower border of azygos vein
Middle	Lower border of azygos vein to lower border of inferior pulmonary vein
Lower	Lower border of inferior pulmonary vein to stomach, including esophagogastric junction
4.2B
cStage Group	cT	cN	cM
Squamous cell carcinoma
0	Tis	N0	M0
I	T1	N0-1	M0
II	T2	N0-1	M0
	T3	N0	M0
III	T3	N1	M0
	T1–3	N2	M0
IVA	T4	N0–2	M0
	T1–4	N3	M0
IVB	T1–4	N0–3	M1
Adenocarcinoma
0	Tis	N0	M0
I	T1	N0	M0
IIA	T1	N1	M0
IIB	T2	N0	M0
III	T2	N1	M0
	T3–4a	N0–1	M0
IVA	T1–4a	N2	M0
	T4b	N0–2	M0
	T1–4	N3	M0
IVB	T1–4	N0–3	M1

^aSubcategories.^bIf further testing of “undifferentiated” cancers reveals glandular components, categorize as adenocarcinoma G3.^cIf further testing of “undifferentiated” cancers reveals squamous cell components, or if after further testing they remain undifferentiated, categorize as squamous cell carcinoma G3.^dLocation is defined by epicenter of esophageal tumor.

From Rice TW, Patil DT, Blackstone EH. 8^th edition AJCC/UICC staging of cancers of the esophagus and esophagogastric junction: application to clinical practice. Ann Cardiothorac Surg. 2017;6(2):119–130.

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