Lymph Nodes Involvement and Lymphadenectomy in Thymic Tumors: Tentative Answers for Unsolved Questions

Abstract

Thymic tumors are the most common primary neoplasms of the anterior mediastinum, although, when compared with the entire thoracic malignancies, they are still rare. Few studies addressed the questions about lymph node involvement pattern in thymic neoplasms, about which subgroup of patients would be appropriate candidates for lymph node dissection or about the extent of lymphadenectomy or which lymph nodes should be harvested. The aim of this review is to collect evidence from the literature to help physicians in designing the best surgical procedure when dealing with thymic malignancies. A literature review was performed through PubMed and Scopus in May 2021 to identify any study published in the last 20 years evaluating the frequency and the extent of lymph node dissection for thymic tumors, its impact on prognosis and on postoperative management. Fifteen studies met the inclusion criteria and were included in this review, with a total of 9452 patients with thymic cancers; lymph node metastases were found in 976 (10.3%) patients in total. The current literature is heterogeneous in the classification and reporting of lymph node metastases in thymic carcinoma, and data are hardly comparable. Surgical treatment should be guided by the few literature-based pieces of evidence and by the experience of the physicians.

Continuing challenges of primary neuroendocrine tumours of the thymus: A concise review

“…It has been shown to be effective in localizing extent of disease and it is useful as a prognostic predictor of response to therapy [30]. However, because 111 In-DTPA-OC also accumulates in thymomas and thymic metastases, its specificity can be poor, both for the primary tumour and for bone metastases, and therefore its use has mostly been superseded by 68 Gallium -DOTATATE PET/CT. Data on the use of 123 MIBG scintigraphy in NETTs is limited, but its performance may be similar to that in other neuroendocrine tumours, with several cases of NETT that were appearing negative on 111 In-DTPA-OC being identified with 123 I-MIBG [37,38].…”

“…As mentioned, 68 Gallium -DOTATATE PET/CT now tends to be the first-line nuclear imaging method for NETTs, due to its high sensitivity and specificity [40]. Although data is scarce, some have stated that 68 Gallium -DOTATATE PET/CT may detect additional NETTs not identified on 18 F-FDG PET/CT [41].…”

“…Conversely than for 18 F-FDG PET/CT, well differentiated NETTs are likely to be more avid than poorly differentiated tumours. Furthermore, high 68 Gallium -DOTATATE PET/CT uptake is needed for peptide receptor radionuclide therapy to be effective [42].…”

“…Newer nuclear medicine imaging agents, such as 68 Ga-fluorodopa(F-D)PA), or 1,4,7,10-tetraazacyclododecane-1,4,7,10tetraacetic acid peptide, as well as radiolabelled ligands such as 64 Cu-DOTA-peptides, which interact with other receptors (GLP-1, bombesin, cholecystokinin, gastric inhibitory polypeptide, integrin, chemokines) have overall shown promising results [43]. Additionally, ( 11 C)-5-hydroxy-tryptophan PET seems to be a promising, imaging modality, yet difficult to apply due to the short half-life of 11 C(28).…”

“…Additionally, ( 11 C)-5-hydroxy-tryptophan PET seems to be a promising, imaging modality, yet difficult to apply due to the short half-life of 11 C(28). Although 18 F-fluoro-L-4-dihydroxyphenylalanine, gallium-68 ( 68 Ga)-tetraazacyclododecanetetraacetic acid-Tyr3-octreotide, 68 Ga-tetraazacyclododecanetetraacetic acid-1-Nal3-octreotide, and 18 F-(1-deoxy-D-fructosyl)-N-(2-[ 18 F]fluoropropionyl)-Lys 0 -Tyr 3octreotate (Gluc-Lys) are available, clinical experience with these agents for their use in NETTs is small [44]. The rates of sensitivity for these various modalities differs widely per study, while patient numbers are limited.…”