Utility of EBUS-TBNA in PET-positive mediastinal lymph nodes in subjects with extra-thoracic malignancy

Abstract

Background/AimPatients with primary extra-thoracic malignancy (ETM) often have hyper-metabolic mediastinal lymph nodes (HM-MLN) in the PET-scan done for initial staging or post treatment follow-up. There is scant data on the etiology of HM-MLN in such patients, which can also be due to non-malignant causes. We used endobronchial ultrasound (EBUS) guided sampling to determine the etiology of HM-MLN in patients with ETM and study the relationship between PET-SUV values and a diagnosis of malignancy in this population.Materials and methods65 consecutive patients, from March 2013 to March 2017 with either known ETM for primary staging or post-treatment follow-up, with PET CT showing HM-MLN (SUV > 2.5) were included in the study.Results65 patients with ETM had EBUS-TBNA for HM-MLN. 20/65 (30.7%) were malignant, 45/65 (69.23%) were benign MLN. In patients with benign etiology of HM-MLN, 6/45 (13.3%) had necrotising granulomatous, 24/45 (53.3%) had non- necrotising granulomatous MLN and 15/45 (33.3%) had reactive MLN. We found discordance (i.e. primary ETM responded to treatment and a new HM-MLN was detected) in 21/65 (32.3%) patients with PET-CT done for initial ETM staging, and 44/65 (67.7%) with a post-treatment PET-CT. showed. Correlating SUV with diagnoses, the SUV values in EBUS-proven malignant MLN were 8.9 ± 4.1, while they were 10.2 ± 5.57 in benign MLN. There was no statistically significant difference between the SUV of benign and malignant MLNs.ConclusionThis study shows a significant incidence of EBUS-TBNA proven benign diagnoses 45/65 (69.2%) in ‘SUV-deemed-malignant MLN’ and a poor relationship between high SUV and malignant MLN, in patients with known ETM. The ETM related HM-MLN have a significant chance of being benign, and a tissue diagnosis is imperative as it impacts on the treatment plan and prognosis.

Importance of mediastinal granulomatous/sarcoid‐like lymphadenopathy in extrathoracic malignancies

“…The frequency of granulomatous MLN in patients with ETM differs between 5.2% and 36.9% 1,8–12 . It was 13.8% in our study.…”

“…Discriminating between granulomatous inflammation and malignancy based on CT and/or PET‐CT findings is difficult. Both are FDG avid 8 and SUV values are similar 11 . However, unilateral or asymmetrical enlargement, presence of coalescence, blurred margins, or necrosis suggest metastasis, lymphoma, or tuberculosis 19,20 .…”

Endobronchial ultrasound-guided transbronchial needle aspiration in intrathoracic lymphadenopathy with extrathoracic malignancy

“…Primary lung cancer with nodal involvement accounts for the majority of mediastinal and hilar lymphadenopathy cases[ 20 ], but Mehta et al [ 13 ] showed a high frequency of benign diagnoses. EBUS-TBNA is considered safe and feasible for tissue sampling with access to both mediastinal and hilar lymph nodes, which is recommended by both the American College of Chest Physicians and European Society of Thoracic Surgeons in primary lung cancer[ 7 , 8 ].…”

“…EBUS-TBNA is also of value for the diagnosis of mediastinal lymphoma[ 11 ]. In clinical practice, EBUS-TBNA could be considered the first-line examination for suspicious mediastinal lymph nodes in patients with extrathoracic cancer, preventing surgery in 50% of them[ 12 ]; in contrast, the use of EBUS-TBNA in intrathoracic lymphadenopathy in patients with extrathoracic solid organ malignancy is a relatively less investigated topic[ 13 , 14 ].…”

An assessment about the adequacy of EBUS in mediastinal lymph nodes accompanying extrathoracic malignancies

“…Previous studies have reported mediastinal and hilar LN showing high metabolic activity associated with sarcoidosis and tuberculosis in patients with ETM (6). There can be a high level of confusion between a primary tumor and mediastinal and hilar LN with increasing activity, or which emerge as a response to malignancy treatment.…”