Ectopic spleen presenting as a slowly enlarging lung nodule in the right lower lobe following gastric pull up operation

Abstract

This is a case report of an elderly man who was investigated at our respiratory clinic for slowly enlarging right lower lobe lung nodule on the background of oesophageal cancer diagnosed more than 11 years ago with gastric pull up. CT guided biopsy confirms the diagnosis of intrathoracic ectopic spleen.

Background

As far as we are aware this is the first case report of ectopic spleen in the right lower lobe (unusual site of intrathoracic ectopic spleen) following gastric pull up. Ectopic spleen should be considered in the differential diagnosis of a lung nodule for any patient with history of upper abdominal operation which involves manipulation of the spleen.

Case presentation

A 78-year-old white man was referred to the respiratory clinic for the management of recurrent exacerbation of bronchiectasis in 2019 presenting as productive cough with purulent sputum requiring several courses of antibiotics with no history of haemoptysis. He has a background of bronchiectasis and moderately severe COPD. He was diagnosed with oesophageal cancer in 2008 for which he underwent radical oesophagectomy and gastric pull up (with no chemotherapy or radiotherapy). He is an ex-smoker for the last 15 years with 20-pack year history. He is a retired builder with possible exposure to asbestos and used to work in a dusty environment. Performance status was around 2. Patient lives independently.

Medications wise the patient was on tiotropium respimate, trimbow inhaler, salbutamol inhaler, carbocisteine, diazepam, clopidogrel, gaviscon, lansoprazole and pregabalin. Sputum sample isolated Haemophilis influenzae which was fully sensitive.

On examination during clinical review in the respiratory clinic, his oxygen saturation was 97% on air, respiratory rate 18/min, blood pressure 130/70 mmHg and heart rate 84/min. On there is no finger clubbing and no cervical lymphadenopathy with equal air entry on chest examination with no wheezes or crackles; heart sounds normal and calves soft, non-tender with no leg swelling.

Investigations

CT chest done in April 2019 showed an incidental 14 mm solid lung nodule in the right lower lobe adjacent to the gastric pull through (figure 1). Review of previous images showed slow and progressive enlargement of this nodule since 2009 (figure 2). Repeat CT chest in September 2019 and January 2020 showed increase in lung nodule size by 35% using volumetric studies.

Figure 1.

CT chest April 2019.

Figure 2.

CT chest 2009.

Pulmonary function test done and showed mild obstructive airway disease. Autoimmune screen including vasculitic screen were negative. CT guided biopsy was done in February 2020 which went uneventfully (figure 3).

Figure 3.

CT guided biopsy of right lower lobe lung nodule.

Histopathological examination demonstrated splenic tissue with normal architecture with red and white pulp. There was no obvious extramedullary haematopoiesis or evidence of malignancy (figures 4 and 5). Diagnosis of ectopic spleen was made.

Figure 4.

Histopathological slide showing splenic tissue with normal architecture of the red pulp with congested sinuses separated by splenic cords and the white pulp constituted by a nodule of small lymphocytes with no germinal centre. H&E 100×.

Figure 5.

Network of venous sinuses highlighted by CD8 reaction. White pulp in the upper right. CD8 100×.

Differential diagnosis

Differential diagnosis of the lung nodule includes lung cancer, either primary or metastasis. In this case oesophageal cancer recurrence or metastasis is considered but this was unlikely given the slow progression of the lung nodule and long-time interval between the diagnosis of previous oesophageal cancer and the appearance of the lung nodule. Other important differential diagnoses include lymphoma, localised fibrous tumour of the pleura, mesothelioma, haemangioma, carcinoid tumour and teratoma.

Treatment

Conservative approach was followed and no further intervention is planned for the patient.

Outcome and follow-up

The patient was reassured regarding the diagnosis of ectopic spleen and no further intervention or radiological follow-up is need.

Discussion

Ectopic spleen results from autotransplantation of the splenic tissue usually following splenic trauma or splenectomy and occurs in intra-abdominal or extra-abdominal sites.¹ In ectopic spleen, the spleen leaves its normal anatomic position and implants in other locations such as a serosal surface, deriving a local blood supply and developing into nodules of differentiated splenic tissue.²

As per Pérez-Legaz et al the first description of ectopic spleen was reported by Van Horne in 1667 as an incidental autopsy finding. The real incidence of this problem is not known, but its rareness has been documented in a series of 1413 splenectomies where the incidence was 0.16%. It usually presents in middle aged adults and is more common in women in a proportion of 20:1.³

The most common site for ectopic spleen is in the abdomen or pelvis with seeding of the peritoneum, omentum or mesentery. In 18% of patients the ectopic spleen is localised to the thorax; the most common ectopic site in the later case is the pleural surface or sub pleural area of the left lung (usually left lower lobe).⁴ Thoracic ectopic spleen is usually preceded by a history of traumatic injury to the spleen associated with traumatic rupture of the left hemidiaphragm.⁴ Since the first case report in 1937, Kim et al documented that over 57 case reports of thoracic ectopic spleen have been published⁵ but as far as we are aware our case is the first case to report ectopic spleen in the right lower lung following gastric pull up operation. In our patient, this likely to have occurred after small part of the spleen was attached to the stomach wall and transferred to the chest during gastric pull up operation. Other possible way is through haematogenous transfer of the splenic cells and implantation in the pleural surface. Blood supply of the ectopic spleen is established either though a small blood vessel originating from the gastric blood supply or small pleural surface bases blood vessel.

In the majority of patients, thoracic ectopic spleen is usually asymptomatic and diagnosed incidentally during CT imaging as a slowly enlarging pleural based (or subpleural) lung nodule. History of splenic trauma should alert the clinician to the possibility of the diagnosis. Rarely the patient might present with cough, haemoptysis or pleuritic chest pain.⁴ Imaging modality of choice is Technetium Tc 99m heat-damaged erythrocytes scintigraphy scan.⁴ If the scintigraphy scan is not available or not diagnostic then biopsy would be the next step.

Histology of ectopic spleen is the same as a normal spleen and shows normal splenic tissue with white and red pulps. The splenic sinus endothelial cells characteristically immunostain for CD8 (figures 4 and 5).

The usual approach to thoracic ectopic spleen is conservative approach (which we have done in this case) especially for small and asymptomatic ectopic spleen¹; although surgical approach could be an option for a large ectopic spleen causing agonising symptoms.⁶ Histopathological confirmation of the diagnosis is usually required prior to consideration of surgery (though CT guided biopsy).

Given the splenic implants can be partially or even fully functioning tissue with beneficial effect for the immune system of the patient, especially for patients with history of splenectomy, it has been advocated that ectopic spleen should not be removed and aim to follow conservative approach as much as possible.

Learning points.

• Ectopic spleen is a rare entity.

• Ectopic spleen should be considered in the differential diagnosis of any lung nodule in a patient with history of splenic manipulation (most common is splenic trauma or splenectomy).

• Conservative approach is sensible in most of the cases of ectopic spleen.