Virtual Library

Abstract:
In the WHO 2015 classification, neuroendocrine tumors (NETs) have become one of the 4 major histological types of lung cancer. NET includes typical carcinoid (TC), atypical carcinoid (AC), small cell lung carcinoma (SCLC) and large cell neuroendocrine carcinoma (LCNEC). In this presentation, I’ll talk about problems of diagnosis of SCLC, and challenge “common knowledges” of NETs as follows: 1. SCLC is highly malignant and only very rarely the patients survive after 5 years. What are pathological characteristics of tumors with longer survival? 2. There are no subtypes of SCLC, only combined SCLC is described in the WHO 2015. Isn’t subtyping of pure SCLC needed? Also, is SCLC a hilar-type cancer? 3. Diagnosis of SCLC doesn’t require immunohistochemistry (IHC) although IHC is used to diagnose even adenocarcinoma and squamous cell carcinoma. Isnt’ IHC useful for SCLC? 4. NET includes TC, AC, SCLC and LCNEC. Is this a spectrum of NET, showing progression of NET? In other words, does AC progress to LCNEC? 5. For adenocarcinoma diagnosis, transcription factor TTF-1 is useful even when the tumor doesn’t express glandular phenotypes such as mucin and CEA. In case of NET, we usually pay attention to NE phenotypes such as synaptophysin and NCAM, not to transcription factors. Aren’t transcription factors such as ASCL1 and INSM 1 useful for SCLC diagnosis? 6. Is the Kulchitsky an origin of SCLC? I’d like to answer these questions, mainly based on our own experiences.

Abstract:
Neuroendocrine tumors (NETs) are a distinct subgroup of neoplasms arising from the neuroendocrine cells. Due to the peculiar morphological, immunohistochemical and molecular characteristics, NETs are usually classified as a separate group of tumors among solid malignancies. Thoracic NETs include the pulmonary and the thymic NET. Pulmonary NETs (PNETs) comprise well-differentiated neuroendocrine tumors (typical carcinoid), moderately-differentiated neuroendocrine tumors (atypical carcinoid), the latter two grouped as Bronchial Carcinoids (BCs); large cell neuroendocrine carcinoma (LCNEC) and small-cell lung carcinoma (SCLC). There are also two preneoplastic conditions, the Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia (DIPNECH) and the tumorlets whose role in the neuroendocrine carcinogenesis are yet to be fully clarified. PNETs represent about 25% of all lung cancers, most of them represented by SCLC. Thymic NETs (NeuroEndocrine Thymic Tumors, NETT) are considered as a subgroup of thymic carcinoma, although in most series they are classified separately, and are further classified as well-differentiated NETT (typical carcinoid), moderately-differentiated NETT (atypical carcinoid) and poorly-differentiated NETT (Large cell and small cell neuroendocrine carcinoma). NETTs are exceedingly rare and represent about 5% of all thymic tumors. The present lecture will focus on PNETs and NETTs, with a particular insight in the surgical management of these tumors. 1, Pulmonary NETs. The most recent TNM staging classifications of lung cancer (7[th] and 8[th] edition) suggest that PNETs should be staged similarly to Non-Small Cell Lung Cancer (NSCLC). Surgical indications largely depend on histology and stage. Bronchial carcinoids (BCs) represent about 10% of PNETs. The vast majority are typical carcinoids (TC, well-differentiated neuroendocrine tumors); they are usually located centrally in the lung parenchyma/airways (70%), and they are frequently confined to the lung without evidence of loco-regional or distant spread, which occur in about 5-10% of the cases. Atypical carcinoids (AT) share most of the characteristics of typical carcinoids, although they present a higher rate of mytoses and necrosis. They are more aggressive than TCs and they present with lymphnodal metastatic involvement in 30%-50% of the cases. LCNEC are usually diagnosed after resection, since a preoperative characterization on small biopsies is challenging. They are aggressive tumors, and more than 50% of the patients present with an advanced disease at diagnosis, for whom surgery is not indicated. As for SCLC, the vast majority of the patients present at an advanced stage, with hematogenous spread. The role of surgery in the treatment of PNETs is similar to what is currently employed for NSCLC. BCs are often amenable to surgery, due to the early stage at presentation. Anatomical resections (segmentectomy, lobectomy or more extended resections) offer the best outcome, while sublobar wedge resection should be avoided in fit patients, and should be reserved only for patients not amenable to anatomical resections. Parenchymal-sparing techniques (bronchial/vascular sleeve resection) should be employed whenever possible to avoid pneumonectomy in centrally-located tumors. Lymphadenectomy should be carried out according to the current guidelines (IASLC/ESTS), including a minimum of 6 nodes/stations of which 3 mediastinal including the subcarinal one. Endoscopic resection may have a role only in case of lobar/lung atelectasis to restore the bronchial patency before definite surgical resection Endobronchial resection is also employed with palliative intent in unresectable disease. Survival after resection of BCs is excellent, with more than 90% of the patients with typical carcinoids alive at 10 years, and 70% and 50% with atypical carcinoids alive at 5 and 10 years. The role of adjuvant therapy after complete resection of BCs is not fully determined and it is often discussed on an individual basis in a multidisciplinary tumour board setting. LCNEC are poor candidates for surgery, because of the loco-regional and distant spread at presentation. Anatomical resections, including extended resection to neighboring organs are needed in order to achieve a complete resection. Despite this, local recurrence and distant metastases are frequent after surgery. Adjuvant therapy (chemotherapy or chemoradiotherapy) is almost always needed after surgery for the disease control. SCLC has customarily been considered nonsurgical because of the high aggressiveness and the chemosensitivity of this neoplasm. However, in carefully selected patients with limited disease (T1-T2N0) surgery as part of a multidisciplinary protocol (chemoradiotherapy) may be proposed after a careful assessment of loco-regional (including mediastinal) and distant spread. 2, Thymic NETs. Thymic NETs (NETTs) are usually aggressive thymic tumors, very often presenting atypical features (atypical carcinoid). They express somatostatin receptors which may justify the use of Octreotide scintigraphy for the diagnosis and follow-up. About 30-40% have metastases at presentation and in some cases they are associated with endocrinopaties (Cushing syndrome, MEN-1 syndrome, etc). The staging system for NETTs has traditionally been the Masaoka system. The 7[th] edition of the TNM of thymic tumors included also the NETTs. As for other thymic malignancies, surgery is the treatment of choice for local and loco-regional disease (Stage I/II and selected Stage III). The resectability rate for NETTs is far lower than that of thymoma, ranging between 30% and 100% in most series. Complete (R0) resection is the most important prognostic factor. Median sternotomy and open surgical approaches are the optimal accesses for NETTs. The role of minimally-invasive techniques (MIT) in the treatment of NETT is extremely limited, due to the aggressive nature of the tumor. The role of induction and adjuvant treatments (radiotherapy or chemotherapy) has not been established yet, due to the rarity of the condition. 3, The collaborative effort. As for many rare diseases, also for NETs a collaborative, multi-Institutional, society-based effort is the single most important factor that can provide a real advancement in the research and management of this condition. The European Society of Thoracic Surgeons (ESTS) launched in 2012 a Neuroendocrine Tumors Working Group with the aim of collecting data from interested Institutions across the world. An amazing database collating more than 2100 patients has been designed which represents a tremendous opportunity for the study of these rare conditions. A number of studies have been published so far which constitute a solid backbone for the management of NETs.

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