Primary lung tumour invading the chest wall

Abstract

Introduction

This case study describes a primary lung tumour invading the chest wall, that clinically was thought likely to be a lipoma, and was imaged first using ultrasound.

Case Report

A 67 year old male presented to his GP with a six month history of a lump increasing in size on the left upper chest wall. The ultrasound scan demonstrated a hypoechoic and hypervascular soft tissue mass, extending out of the chest into the subcutaneous tissue and starting to erode the overlying rib. The appearances were highly suspicious for a chest malignancy. Further imaging and an ultrasound guided biopsy confirmed the diagnosis of a squamous cell carcinoma.

Discussion

The majority of patients who present to their general practitioner with a soft tissue mass commonly have benign abnormalities such as a lipoma or epidermoid cyst. Tumours of the chest wall are varied and are divided into benign and malignant tumours, and those that arise from the rib cage. Primary lung tumours are uncommonly seen on ultrasound. Lung cancers account for around 20% of all cancer deaths and the chest wall is involved in around 5% of primary lung tumours.

Conclusion

This case highlights the need for prompt investigation of enlarging superficial masses. Ultrasound imaging offers excellent detail for superficial structures and in this case, due to the location of the mass, identified a primary lung tumour.

Introduction

Lung cancers account for around 20% of all cancer deaths, and the chest wall is involved in around 5% of primary lung tumours. The symptoms of lung cancer can be varied, although the most common include unexplained weight loss, a long-standing cough, breathlessness and haemoptysis. Traditionally, the first line test is a chest radiograph followed by computed tomography (CT) to assess the lungs in greater detail. This case study reports on a lung squamous cell carcinoma that was initially detected on ultrasound, which clinically was thought to represent a lipoma. A detailed assessment of patient history, clinical care pathway, diagnostic imaging and discussion on lung cancer are presented.

Case study

A 67-year-old male presented to his general practitioner (GP) with a palpable left upper chest wall lump and was subsequently referred for a soft tissue ultrasound scan of this area. Clinically, this was thought to represent a lipoma but ultrasound was deemed necessary for clarification.

During the examination, the patient reported that the mass had been present for six months. The mass was increasing in size and was not painful. The patient did not report a history of trauma although had unintentionally lost weight over the last 12 months. He did not have any underlying health conditions and was a smoker. The ultrasound scan showed a well-defined hypoechoic and irregular soft tissue mass extending out of the chest cavity. The mass was also infiltrating the chest wall musculature and subcutaneous tissue (Figure 1). As the dermis and subdermal tissues were preserved, this indicated that the mass was arising from the chest cavity and invading surrounding soft tissue structures rather than a superficial mass infiltrating the chest cavity. The mass demonstrated internal vascularity on colour Doppler imaging (Figure 2). There was cortical irregularity of the overlying rib, suggesting the mass was also eroding the rib. The appearances were suspicious for a lung malignancy with local invasion of surrounding structures and rib erosion. The patient had a chest radiograph, which confirmed an opacity in the left upper zone (Figure 3), and was referred to the Chest multidisciplinary team (MDT) for further management. Following discussion, the patient was sent for a staging CT scan, which confirmed the ultrasound findings of a lung malignancy invading surrounding tissues and rib erosion (Figure 4). The CT scan also identified mediastinal lymphadenopathy, demonstrating this was an aggressive malignancy with local metastatic spread. The patient had an ultrasound-guided biopsy, and the histology gave a definitive diagnosis of squamous cell carcinoma. As the cancer was diagnosed at an advanced stage, the patient was given palliative treatment of a combination of both radiotherapy and chemotherapy.

Figure 1.

Longitudinal ultrasound image of the upper chest wall, showing a well-defined hypoechoic mass extending out of the chest wall with a rib erosion (arrow).

Figure 2.

Transverse ultrasound image of the upper chest wall mass demonstrating internal vascularity with the appearances suspicious for malignancy.

Figure 3.

Chest radiograph with an opacity in the left upper zone (arrow).

Figure 4.

CT scan showing an anterior left upper lobe mass (red arrow) with chest wall infiltration and erosion of left anterior third rib (red arrowhead). Local lymphadenopathy (blue arrowheads) can also be identified.

Discussion

There are around 47,800 cases of lung cancer in the UK every year, with 86% of cases linked with smoking. ¹ In this case study, the patient was a smoker and had lost weight unintentionally over the last 12 months, although had no other underlying health conditions. Other risk factors include occupational exposure, diet, air pollution, previous lung disease and genetic and immunological factors. ² In 2015, 35,000 people died from lung cancer in the UK. ³ Around 54% of lung cancer deaths in the UK are in males and 46% in females. Lung cancer is strongly linked with age with incidence rates rising steeply from around age 45–49 and peak incidence in females is 80 to 84 years and in males is 85 to 89 years. ¹

Lung cancer is classified as non-small cell lung cancer and small cell lung cancer. Non-small cell lung cancer accounts for around 80% of all lung cancers. ² Non-small cell lung cancers are divided into three main subgroups, which are adenocarcinoma, squamous cell carcinoma and large cell carcinoma. ⁴ Within these subgroups, squamous cell carcinomas account for around 25–30% of all non-small cell lung cancers. ⁵ Squamous cell carcinomas are more aggressive lung cancers with local spread. ⁶ In this case, the lung cancer had locally invaded the chest wall musculature and subcutaneous tissue with mediastinal lymphadenopathy.

Only 5% of all primary lung cancers involve tumour infiltration of the chest wall. ⁷ There is a paucity of evidence with regard to the effectiveness of ultrasound assessment of chest wall infiltration. A study of 114 patients reported that ultrasound detected signs of chest wall invasion in 68.42% patients whereas CT detected changes in 72.8%. ² Another smaller study of 54 patients reported there was no significant difference in identifying chest wall invasion with ultrasound detecting changes in 20.8% patients whereas CT detected this in 11.3% patients. ⁸ Ultrasound in this case could not identify the mediastinal lymphadenopathy, and the full staging and assessment of lung cancers should be made with CT. When scanning soft tissue masses, it is important to not only assess the soft tissues but also assess bony structures. This case demonstrated cortical irregularity and a defect in a rib caused by the lung tumour. This additional feature increased the suspicion for malignancy. In practice, bony metastases can also be identified on ultrasound although this should be confirmed on cross-sectional imaging such as CT. ⁹

Non-small cell lung cancers are commonly diagnosed at an advanced stage. ² This explains why the five-year survival rate is low, recorded at around 16% although this is dependent on how early the disease is detected. ¹⁰ The most common symptoms of lung cancer include a long-standing cough, weight loss and haemoptysis. ¹¹ In this case, the only symptoms were weight loss and a painless lump that was increasing in size. Due to this lack of symptoms, unfortunately the diagnosis of lung squamous cell carcinoma was made at a late stage and therefore only palliative treatment was the option for the patient. For patients with a suspected lung cancer, the first-line test is a chest radiograph. In this case, the chest radiograph identified an opacity in the left upper zone but only after initial analysis of the lump using ultrasound. Most lung cancers, as in this case, are diagnosed and staged using CT. CT is important, as it guides clinicians on treatment options available to patients on an individual basis. Treatment options include surgical excision for cancers diagnosed at an early stage. Those at an advanced staged are offered commonly a palliative combination of chemotherapy and radiotherapy. The patient in this case was offered palliation due to the late presentation and diagnosis.

Clinically, the soft tissue mass on the chest wall was suspected to represent a lipoma and the GP requested an ultrasound scan for clarification. The National Institute for Health and Care Excellence (NICE) advises that a direct access ultrasound scan should be performed within two weeks to assess adults presenting with an unexplained lump. ¹² The majority of these lumps will be lipomas but this patient had a chest wall mass that was increasing in size and was a smoker, which are risks enough to be referred onto a cancer care pathway. In departments with high waiting times, delays whilst waiting for an ultrasound scan may have detrimental effects on patient management. Fortunately in this case, the patient had ultrasound and chest radiography on the same day and was referred to the Chest MDT to investigate further without delay.

Conclusion

This case study demonstrates the ultrasound features of an advanced lung cancer infiltrating the chest wall, which was thought to be a common benign subcutaneous lipoma. The importance of an early diagnosis of lung cancer is fundamental, as this significantly impacts on the treatment options available for patients. Ultrasound is a useful first-line test for patients presenting with a soft tissue mass. Patients with a suspected malignancy must be referred directly onto a cancer care pathway.