Unexpected complication in a patient submitted to pulmonary radiofrequency ablation

Clinical History

A 53-year-old male patient with a pulmonary nodule (3cm) histologically proven as non-small-cell-lung-cancer (NSCLC) underwent Radiofrequency-Ablation (RFA) under CT guidance (Fig.1a-b). No acute complications occurred (Fig.2a-b). During 18th postprocedural-day patient suffered from sudden dyspnoea, fever, thoracic pain, swollen chest and presented crunchy feeling on palpation. Biochemical tests revealed low oxygen-saturation (88%) and respiratory acidosis.

Imaging Findings

CT performed at admittance to our Centre showed the needle-tract connecting a bronchus through the treated lesion with the pleural space (Fig.3a) and also with the subcutaneous tissue (Fig.3b), creating massive subcutaneous emphysema (Fig.3c). CT demonstrated also the presence of antero-superior pneumomediastinum deriving from air along the course of internal mammary vessels (Fig.3d-e).
Due to the worsening of clinical condition, a further CT evaluation was performed revealing the appearance of pneumothorax (Fig.4a-c).
A transthoracic drainage was then successfully performed (Fig.5a). However, the patient died from septic complications.

Discussion

RFA is a minimally invasive technique which involves inserting a needle through the chest wall into the lesion and administering electromagnetic radiation which is absorbed by the tissue as heat and results in necrosis; it is an alternative to radiation for palliative cancer therapy with relatively minimal procedure-related complications [1, 2].
RFA is indicated in patients with early-stage (T1–T2, N0, M0) NSCLC who are not eligible for surgery because of coexisting morbidity; in patients with late-stage NSCLC; in patients who underwent surgical treatment for NSCLC and in whom tumour has recurred; and in patients with metastatic lung disease [3].
On the immediate post-treatment CT, the hypodense area representing the necrotic tumour is generally surrounded by a ground-glass area, which seems to correspond to a thin layer of heat-damaged normal lung parenchyma [4].
Follow-up CT images are obtained to evaluate the changes in the enhancement pattern, lesion size, lymph node metastasis, and complications.
Possible reported complications include: pneumothorax not requiring a chest tube (9%-57%), pneumothorax requiring a chest tube (3%-20%), pleural effusion (13%-19%), bronchopleural fistula (<1%), needle-tract seeding (<1%), brachial nerve injury (<1%), pulmonary artery pseudoaneurysm (<1%) [5, 6]. These complications might be divided in major and minor according to the Society of Interventional Radiology (SIR) classification [7]. Any event associated with high morbidity and mortality or requiring an increase in treatment or prolonged hospitalisation is considered a major complication.
Moreover blood transfusion and the necessity of drainage define a complication as major. All other complications are minor ones.
The presence of massive subcutaneous emphysema of the chest wall associated with pneumomediastinum and hypertensive pneumotorax,as in our case, is a very rare complication: in particular, the association of chest wall massive subcutaneous emphysema and pneumomediastinum is mentioned only in one case in literature[2].
The pathological processes which might cause pneumomediastinum and subcutaneous emphysema are mainly two: the destruction of the tumour lesion, which allows air to track through the damaged interstitium, dissect through the connective tissue planes and involve both the mediastinum and subcutaneous tissue; the creation of a fistula between the cavitary mass and the pleural cavity, communicating with the subcutaneous tissue and mediastinum through the needle tract, as in our case [2].
The area within internal mammary vessels run is a least resistance way: this "locus minoris resistentiae" is probably the reason why the air ploughes through this area, reaching the mediastinum and creating pneumomediastinum.

Differential Diagnosis List

Final Diagnosis

Pneumothorax, subcutaneous emphysema and pneumomediastinum in patient submitted to pulmonary-RFA.

URL:	https://www.eurorad.org/case/9717
DOI:	10.1594/EURORAD/CASE.9717
ISSN:	1563-4086