Neuroendocrine tumors of the bronchopulmonary tract: a reappraisal of their classification after 20 years

Added value of spectral parameters for the assessment of lymph node metastasis of lung cancer with dual-layer spectral detector computed tomography

Background

Lymph node (LN) metastasis is an important factor affecting the treatment of lung cancer. The purpose of this article was to investigate the benefits of dual-layer spectral detector computed tomography (SDCT) for the evaluation of metastatic LNs in lung cancer.

Methods

Data from 93 patients with lung cancer who underwent dual-phase enhanced scanning with SDCT were retrospectively analyzed. According to the pathological findings, 166 LNs were grouped as metastatic (n=80) or non-metastatic (n=86). LNs in station 4 (n=80) and station 7 (n=35) accounted for the majority of the LNs (approximately 69.23%). The short-axis diameter of the LN, arterial enhancement fraction (AEF), normalized iodine concentration (NIC), and the slope of the spectral Hounsfield unit curve (λ_HU) during the arterial phase (AP) and venous phase (VP) were measured. The Mann-Whitney U test was used to statistically compare these quantitative parameters. Receiver operating characteristic (ROC) curves were plotted to identify the cutoff values, and decision curve analysis (DCA) was performed to determine the net benefit of each parameter. The diagnostic performance, obtained by combining the short-axis diameter with each of the above parameters, was also studied.

Results

The short-axis LN diameter, AEF, NIC, and λ_HU during the AP and VP all showed significant differences between the metastatic and non-metastatic groups (P<0.05). Of the parameters, the AEF had the greatest diagnostic efficiency for metastatic LNs [area under the ROC curve (AUC)_AEF =0.885] with a threshold of 86.40%. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and 95% confidence interval were 90.00%, 89.53%, 88.89%, 90.59%, and 0.830-0.944, respectively. When the quantitative parameters were combined with the short-axis diameter, the AUCs of the parameters, except the AEF, were significantly improved (P<0.05).

Conclusions

The iodine quantitative parameters from SDCT, such as the AEF, demonstrated high diagnostic performances in the differentiation of metastatic and non-metastatic LNs.

[Multidetector computed tomography assessment of the degree of differentiation of bronchial carcinoid tumors]

OBJECTIVE

To define the CT findings for bronchial carcinoid tumors and to determine whether these findings enable these tumors to be classified as typical or atypical.

MATERIAL AND METHODS

We reviewed the chest CT studies performed between 1 January 2001 and 31 December 2009 in patients at our hospital diagnosed with bronchial carcinoid tumors. The sample consisted of 52 patients (23 women and 29 men) with a mean age of 47 years (range 11-77 years). The 52 cases were classified as typical or atypical on the basis of the following radiological findings: size, location, focality, type of growth, calcifications, signs secondary to bronchial obstruction, and the presence of significant lymph node enlargement or metastases. These findings were then compared with the histological findings.

RESULTS

Typical carcinoid tumors were the most prevalent (46 cases). The variables associated with atypical tumors were: male sex, advanced age at onset, and size >3cm. The accuracy of CT in classifying atypical tumors correctly increased with the number of variables indicative of atypical carcinoid tumors. A negative result for atypical nature made it possible to rule out an atypical carcinoid tumor in 95% of the cases.

CONCLUSION

CT is useful for defining and characterizing carcinoid tumors into typical or atypical, although a precise formula for differentiating between the two types remains to be defined.

[Trends in prognostic factors for neuroendocrine lung tumors]

OBJECTIVE

The aim of this study was to analyze trends in a variety of prognostic factors for neuroendocrine lung carcinomas through analysis of 2 groups of surgically treated patients.

PATIENTS AND METHODS

Group A contained the first 361 patients, treated between 1980 and 1997. That group was analyzed retrospectively and contained 261 patients with typical carcinoid tumors, 43 with atypical carcinoid tumors, 22 with large-cell neuroendocrine carcinoma, and 35 with small-cell neuroendocrine carcinoma. Group B contained 404 patients enrolled prospectively between 1998 and 2002: 308 with typical carcinoid tumors, 49 with atypical carcinoid tumors, 18 with large-cell neuroendocrine carcinoma, and 29 with small-cell neuroendocrine carcinoma. The following clinical variables were considered: sex, mean age, tumor site, tumor size, lymph node involvement, stage, metastasis, and local recurrence. The 1997 TNM classification was used for staging of lung cancer and survival analysis was performed along with assessment of factors influencing survival. Statistical analysis of the data involved univariate and multivariate analysis.

RESULTS

In both groups, significant differences were observed between patients with typical and atypical carcinoid tumors in terms of mean age, tumor size, node involvement, and recurrence. In group A, female sex, node involvement, and recurrence differed between patients with atypical carcinoid tumors and those with large-cell neuroendocrine carcinoma; the same was true for group B, with the exception of lymph node involvement. Node involvement differed between patients with small-cell versus large-cell neuroendocrine carcinoma in group A but not group B. Both groups displayed significant differences in overall survival and survival of patients with lymph node involvement between patients with typical and atypical carcinoid tumors and between patients with atypical carcinoid tumors and those with large-cell neuroendocrine carcinoma; no differences were observed between patients with large-cell versus small-cell neuroendocrine carcinoma. Histological type and lymph node involvement had the greatest influence on prognosis in the multivariate analysis.

CONCLUSIONS

A well-defined trend is observed in prognostic factors for neuroendocrine lung tumors. Histological type and lymph node involvement show the greatest influence on survival.

The role of somatostatin analogues in the treatment of neuroendocrine tumours

Neuroendocrine tumours belong to a heterogeneous family of neoplasms, originating in endocrine glands (such as the pituitary, parathyroid or the neuroendocrine adrenal glands), in endocrine islets (within the thyroid or pancreas) as well as in endocrine cells dispersed between exocrine cells throughout the digestive or respiratory tracts. The clinical behaviour of neuroendocrine tumours is variable; they may be functioning or not functioning, ranging from well-differentiated slow growing neuroendocrine tumours to poorly differentiated neuroendocrine tumours, which are highly aggressive malignant tumours. The development of somatostatin analogues as important diagnostic and treatment tools have revolutionised the clinical management of patients with neuroendocrine tumours. However, although symptomatic relief and stabilisation of tumour growth for various periods of time are observed in many patients treated with somatostatin analogues, tumour regression is rare. Development of new somatostatin analogues and new drug combination therapies should further improve the clinical management of these patients.

Neuroblastoma and other neuroendocrine tumors

Neuroblastoma is the most common extracranial solid tumor of childhood. It commonly presents in children younger than 2 years of age, with 90% being younger than 5 years of age. There is marked variability in clinical behavior ranging from spontaneous regression or differentiation into benign tumors to rapid and progressive fatal disease. Approximately 50% of patients will have metastases at presentation. The management is dependent on age, stage of disease, and biological and biochemical markers. Nuclear medicine plays an important role in the initial staging, as a prognostic indicator, for assessment of response to treatment, and also in therapy. The most common nuclear medicine diagnostic studies are (99m)Tc-disphosphonate bone scintigraphy and (123)I-MIBG (metaiodobenzylguanidine) scintigraphy. Bone scintigraphy has been the main investigational modality to diagnose skeletal metastases. Whole body imaging with (123)I-MIBG has become the preferred diagnostic test because this agent accumulates in neuroblastoma in 90% to 95% of cases and will accumulate in the primary tumor and metastases particularly in bone, bone marrow, lymph nodes, and soft tissues. MIBG can be used to assess therapy response and is a significant prognostic indicator. Other diagnostic techniques include positron emission tomography (PET)/computed tomography, mainly using (18)F-fluorodeoxyglucose. Other more experimental PET agents, as well as radiolabeled antibodies and octreotide, also are being investigated. Therapy has mainly focused on palliation and has been used alone or in combination with chemotherapy in high-risk refractory or relapsed patients. Major attention is being placed on stratification of patients to try and reduce the side effects associated with intensive megatherapy in the low to intermediate risk patients. Neuroendocrine tumors (NETs) are rare in childhood, but nuclear medicine techniques, mainly using MIBG and somatostatin receptor agents, have a role in diagnosis, staging, and a limited role in therapy. Newer radiopharmaceuticals, including PET agents, are being evaluated for the assessment of NET. Nuclear medicine techniques play a major role in the management of neuroblastoma and NET.

Bronchial typical carcinoid tumors

The current WHO classification of lung tumors recognizes bronchial typical carcinoid as low-grade neuroendocrine tumors. These tumors grow slowly but can metastasize to regional nodes (4 to 20%) and more rarely to extrathoracic sites. Symptoms are usually related to local compression and obstruction of the bronchial tree. Paraneoplastic syndrome can be present (carcinoid syndrome, Cushing's syndrome, acromegaly). Preoperative diagnosis is usually obtained with bronchoscopic biopsy. Computed tomography and somatostatin receptor scintigraphy are useful in the preoperative staging. Only selected cases can be treated endoscopically with laser resection. The complete surgical resection remains the only therapy with curative intent in the majority of patients. Parenchyma-sparing resections are indicated whenever possible. Overall survival after surgery is excellent (5-year rate, 87 to 100%) with low recurrence rate (2 to 11%). N-status and type of resection seem not to affect prognosis. Local relapse can be treated successfully with surgery, whereas distant metastases have a poor prognosis even after chemotherapy.

Well-Differentiated Neuroendocrine Carcinomas: The Spectrum of Histologic Subtypes and Various Clinical Behaviors

The term "well-differentiated neuroendocrine carcinoma" was coined to describe a variety of demonstrably neuroendocrine tumors which were more aggressive (both with respect to their histologic appearance and their clinical course) than (typical) bronchial carcinoids but were also clearly distinguishable from small cell neuroendocrine carcinomas. This umbrella term encompasses a variety of tumors previously described by a variety of terms including "atypical" carcinoids, "malignant tumorlets," peripheral stage I small-cell carcinoma, as well as neoplasms described simply as "undifferentiated carcinoma" (prior to the recognition of their neuroendocrine properties). As such, this term is a broad term and is not simply synonymous with "atypical carcinoid." Over time, at least 3 subtypes have been identified based upon their histologic appearance and mitotic index, with correspondingly aggressive clinical courses.

Neuroendocrine tumors of the lung: clinical, pathologic, and imaging findings

Neuroendocrine tumors of the lung arise from Kulchitzky cells of the bronchial mucosa and comprise typical carcinoid, atypical carcinoid, large cell neuroendocrine carcinoma (LCNEC), and small cell lung cancer (SCLC). At histopathologic analysis, these tumors demonstrate a progressive increase in the number of mitotic figures per 10 high-power fields of viable tumor and in the extent of necrosis, with typical carcinoid having the lowest values and SCLC having the highest. Typical carcinoid is less aggressive than atypical carcinoid, although these tumors have similar gross pathologic and radiologic features; LCNEC has a prognosis between that of atypical carcinoid and that of SCLC. SCLC is the most aggressive pulmonary neuroendocrine tumor and has the most specific imaging feature: mediastinal or hilar lymphadenopathy. At CT, carcinoid tumors appear as a spherical or ovoid nodule or mass with a well-defined and slightly lobulated border. When nonspherical, the tumor is elongated with its long axis parallel to adjacent bronchi. Calcification or ossification is seen in up to 30% of cases. The CT findings of LCNEC are nonspecific and are similar to those of other non-small cell lung cancers. Although there are some overlapping features between these tumors, integration of the clinical and imaging features may be helpful in differentiation of pulmonary neuroendocrine tumors.

Pulmonary carcinoid tumors

Carcinoid tumors of the lung are an uncommon group of neoplasms of neuroendocrine origin. Pulmonary carcinoid tumors are typically benign and slow growing. However, more aggressive subtypes may develop early nodal and distant metastases. Although several histologic classification strategies have been proposed to distinguish benign from more aggressive subtypes, the lack of uniformity in terminology has resulted in increased ambiguity and confusion. Because these tumors are generally resistant to chemotherapy, complete surgical resection is the primary form of therapy. Long-term survival for patients with typical carcinoid is excellent but is decreased in those with the atypical subtype. Complete tumor resection with preservation of uninvolved pulmonary parenchyma remains the fundamental goal in the surgical treatment of this unusual clinical entity.