Pulmonary carcinoid presenting in pregnancy with an unusual radiological feature

Abstract

Pulmonary carcinoid tumours are a rare form of malignancy that often present with clinical heterogeneity and are challenging to diagnose. Diagnosis during pregnancy is further complicated by delays in imaging and procedures to minimise harm to the fetus. This case describes a primigravid healthcare worker who was diagnosed with pulmonary carcinoid in her first trimester of pregnancy, with particular focus on the unique radiological findings of subpleural blebs as a feature.

Background

Pulmonary carcinoid tumours are a rare type of primary lung malignancy that are classified into typical carcinoid (TC) and atypical carcinoid (AC), depending on mitotic rate and features of necrosis histologically, as per WHO classification.

Clinically, these tumours can present broadly; ranging from often asymptomatic, to wheeze, shortness of breath and recurrent pneumonias. Carcinoid syndrome, Cushing’s syndrome and acromegaly are uncommon.¹ This can be more difficult to recognise in pregnancy, as shortness of breath may be due to physiological changes in pregnancy.

TC has a better prognosis than AC. Ferolla et al described the overall survival for patients with TC as 98.2%, 95.8% and 83.9% at 5, 10 and 15 years, respectively, compared with those with AC, which was 71.6%, 57.3% and 24%.² Metastatic disease is more commonly seen in AC. In a retrospective review, metastatic disease was seen in 16/80 (20%) of patients with AC compared with 13/220 (6%) of patients with TC.³

Gallium-68 DOTATATE positron emission tomography (PET) is the main imaging modality for staging. Radiation exposure is undoubtedly a concern for the fetus. The estimated effective dose of a gallium-68 DOTATATE PET is approximately 1.4 mSv.⁴ The procedure also includes a low-dose CT, with an estimated dose of 5.8 mSv, with an overall dose of 6.2 mSV. This is well below the 100 mSv threshold, above which adverse events, such as spontaneous abortion, congenital malformation and brain maldevelopment, can be seen.⁵ The radiation from a CT pulmonary angiogram is approximately 9.0 mSv.⁶

Surgery may be curative for resectable disease. Surgery during pregnancy is associated with an increase in fetal loss rates as a risk from the anaesthesia.⁷

Case presentation

A 32-year-old primigravid healthcare worker presented at 16 weeks’ gestation with a single episode of large volume haemoptysis associated with shortness of breath and wheeze. There was no chest pain or fevers, and no prior history of venous thromboembolism. She was a never-cigarette smoker and had a prior diagnosis of asthma, manifesting as intermittent wheeze and dyspnoea.

On examination, she had decreased air entry at the left upper zone. She had a sinus tachycardia of 120 beats/min, saturating at 98% on room air and was afebrile.

An initial chest X-ray was performed showing left upper lobe consolidation. A CT pulmonary angiogram demonstrated a tumour mass arising from the distal left main bronchus, measuring 35×25 mm with invasion into the mediastinum and complete collapse of the left upper lobe. There was attenuated vasculature of the hyperexpanded left lower lobe, multiple left-sided subpleural blebs and a left small loculated medial pneumothorax. There was thickening and irregularity of the left visceral pleura. The right lung was normal and there was no pulmonary embolism (CT images—figures 1 and 2).

Figure 1.

Axial view CT chest showing left upper lobe collapse, subpleural blebs and small loculated medial pneumothorax.

Figure 2.

Coronal view CT chest showing left endobronchial lesion and partial view of left upper lobe collapse.

She had a bronchoscopy showing a large globular mass at the distal left main bronchus, which was completely occluding the lumen (figure 3). The lesion was partially debulked and biopsy showed typical pulmonary carcinoid with a proliferation index (Ki-67)<2%. A gallium-68 DOTATATE PET scan was delayed until postdelivery.

Figure 3.

Endobronchial view of large obstructive globular mass arising from the distal left main bronchus.

During the pregnancy, she had a further therapeutic debulking bronchoscopy with re-expansion of the left lower lobe. A repeat inspection bronchoscopy showed stable intraluminal disease at 22 weeks’ gestation. There were no further episodes of haemoptysis and the patient remained well throughout pregnancy. She had an uncomplicated induced vaginal delivery at 38 weeks’ gestation and gave birth to a healthy baby boy.

Postdelivery, gallium-68 DOTATATE PET scan showed an intensely avid left upper lobe mass with no nodal or metastatic disease (figure 4). She had a left upper lobe sleeve lobectomy. There was no lymph node involvement on sampling. Histology confirmed TC, with a mitotic rate of less than 2/2 mm² and no evidence of necrosis (figure 5). Macroscopic findings from the upper lobe showed multiple pleural blebs, corresponding to the CT findings (figure 6).

Figure 4.

Axial view of gallium-68 DOTATATE positron emission tomography scan showing intensely GaTate avid left upper lobe lung mass.

Figure 5.

H&E-stained microscopic section (original magnification 400×) confirming typical carcinoid tumour without evidence of necrosis and a mitotic rate of less than 2/2 mm². The tumour has a trabecular and organoid growth pattern, with uniform tissue cytomorphology.

Figure 6.

Serial sections of the left upper lobe from superior to inferior. Cut sections 13–16 show a rounded, firm, tan tumour measuring 20×20×20 mm. Multiple pleural blebs are seen in sections 9 (IC), 14 and 15 (IH).

Investigations

Admission blood tests:

Normal complete blood count, electrolytes, liver function and inflammatory markers.

CT pulmonary angiogram:

Distal left main bronchus tumour measuring 35×25 mm with invasion into the mediastinum and associated left upper lobe collapse.

Gallium-68 DOTATATE PET:

Intensely avid left upper lobe mass, with no evidence of nodal or metastatic disease.

Bronchoscopy:

Large globular mass at the distal left main bronchus, which was completely occluding the lumen. Biopsy showed typical pulmonary carcinoid.

Pulmonary function tests (postdelivery):

Spirometry, lung volumes and diffusion capacity within normal limits with no acute bronchodilator response.

Treatment

An uncomplicated left upper lobe sleeve lobectomy was performed. There was no lymph node involvement on sampling.

Outcome and follow-up

The patient was discharged 3 days postoperatively with good recovery. She will be followed up by the respiratory team with serial chest imaging. Baby and mother are doing well at 4 months.

Discussion

Six reports of pulmonary carcinoid during pregnancy were found in the literature between 1984 and 2016.⁸ One patient had tracheal carcinoid, needing an emergency caesarean section and subsequent surgical resection at 29 weeks’ gestation. There were no complications to the infant. Another patient had an emergency caesarean section at term followed by a pneumonectomy with fetal survival. All other cases had uncomplicated elective caesarean sections at term with fetal survival.

The effect of carcinoid on pregnancy is not known. Certainly, in the pulmonary carcinoid series, there was no evidence of disease progression during pregnancy with favourable maternal and fetal outcomes. Other sites of carcinoid, particularly primary uterine and metastatic hepatic carcinoid disease, were associated with fetal loss, possibly due to the effects of hormones, such as serotonin, adrenocorticotropic hormone and cortisol on the smooth muscle and placenta.⁸

The CT findings of this case are unique. Pneumothoraces as a presenting feature of pulmonary carcinoid have been described in multiple case reports.^{9 10} The specific finding of subpleural blebs has not been documented in the literature. Radiologically, the appearance of bronchial carcinoid is largely dependent on the location. Endobronchial lesions can be associated with features of bronchial obstruction.¹¹ Obstructive lesions can cause air trapping and overinflation secondary to the ‘expansile check valve’ effect first described by Chevalier Jackson in 1950.¹² It was proposed that dynamic airway changes during respiration result in inspiration causing an opening past the obstruction that is closed by expiration, leading to distal air trapping. Over time, focal hyperinflation and emphysematous changes may develop. Expiratory and other respiratory manoeuvres that increase intrathoracic pressure increase alveolar pressure causing rupture and pneumothorax.¹³ Subpleural blebs are small intrapleural airspaces measuring around 1–2 cm in diameter and are formed by subpleural alveolar rupture due to increases in alveolar pressure and stretching of the alveolar wall. They are mostly found in the apices of the lungs and their outer walls are contiguous with the visceral pleura. Subpleural blebs can be seen in up to 6% of healthy individuals.¹⁴ In this case, they were present only on the side of the pathology, thus unlikely to be an incidental finding. It is postulated that the presence of an endobronchial obstruction resulted in air trapping and focal hyperinflation due to the ‘expansile check valve’ effect. This resulted in an increase in alveolar pressures, stretching of the alveolar wall and the subsequent formation of subpleural blebs. This can be seen on the CT pulmonary angiogram and the corresponding macroscopic slices of the resected lobe (figure 5).

Learning points.

• Pulmonary carcinoid presenting in pregnancy is rare and challenging to diagnose and manage.

• The effect of pulmonary carcinoid on pregnancy is unclear; however, literature has reported generally favourable maternal and fetal outcomes.

• Subpleural blebs are an unusual radiological finding in association with pulmonary carcinoid, and it is postulated that their formation is a postobstructive phenomenon resulting from the ‘check valve’ effect.

• Chronic air trapping and hyperinflation can lead to rupture of subpleural blebs and cause pneumothorax.