ACTH-producing tumorlets and carcinoids of the lung: clinico-pathologic study of 63 cases and review of the literature

A clinical perspective on ectopic Cushing's syndrome

Cushing's syndrome (CS) refers to the clinical features of prolonged pathological glucocorticoid excess. About 10-20% of individuals with CS have ectopic CS (ECS), that is, an adrenocorticotropin (ACTH)-producing tumour outside the pituitary gland. ACTH-secreting neuroendocrine neoplasia (NENs) can arise from many organs, although bronchial NEN, small cell lung cancer (SCLC), pancreatic NEN, thymic NEN, medullary thyroid cancer (MTC), and pheochromocytoma are the most common. Patients with ECS frequently present with severe hypercortisolism. The risk of life-threatening complications is high in severe cases, unless the hypercortisolism is effectively treated. A good outcome in ECS requires a methodical approach, incorporating prompt diagnosis, tumour localization, control of cortisol excess, and resection of the primary tumour when possible.

Updates on lung neuroendocrine neoplasm classification

Lung neuroendocrine neoplasms (NENs) are a heterogeneous group of pulmonary neoplasms showing different morphological patterns and clinical and biological characteristics. The World Health Organisation (WHO) classification of lung NENs has been recently updated as part of the broader attempt to uniform the classification of NENs. This much-needed update has come at a time when insights from seminal molecular characterisation studies revolutionised our understanding of the biological and pathological architecture of lung NENs, paving the way for the development of novel diagnostic techniques, prognostic factors and therapeutic approaches. In this challenging and rapidly evolving landscape, the relevance of the 2021 WHO classification has been recently questioned, particularly in terms of its morphology-orientated approach and its prognostic implications. Here, we provide a state-of-the-art review on the contemporary understanding of pulmonary NEN morphology and the potential contribution of artificial intelligence, the advances in NEN molecular profiling with their impact on the classification system and, finally, the key current and upcoming prognostic factors.

Heterogeneity of TPIT expression in ACTH-secreting extra-pituitary neuroendocrine tumors (NETs) supports the existence of different cellular programs in pancreatic and pulmonary NETs

Extra-pituitary ACTH secretion is associated with a variety of neoplastic conditions and may cause the so-called ectopic ACTH-dependent Cushing syndrome (CS). The clarification of the mechanisms of extra-pituitary ACTH expression would provide potential therapeutic targets for this complex and severe disease. In the adenohypophysis, the transcription factor TPIT, co-operating with other molecules, induces POMC expression and ACTH production. However, no data are currently available on the presence and role of TPIT expression in extra-pituitary ACTH-producing neoplasms. This study was designed to explore TPIT expression in a series of pulmonary and pancreatic ACTH-producing tumors, either CS-associated or not. Forty-one extra-pituitary ACTH-producing neuroendocrine tumors (NETs) were included in the study, encompassing 32 NETs of the lung (LuNETs), 7 of the pancreas (PanNETs), and 2 pheochromocytomas. Of these, 9 LuNETs, all PanNETs, and the two pheochromocytomas were CS-associated. For comparison, 6 NETs of the pituitary gland (PitNETs; 3 ACTH-secreting and 3 ACTH-negative) and 35 ACTH-negative extra-pituitary NETs (15 Lu-NETs and 20 PanNETs) were analyzed. Immunohistochemistry with specific anti-TPIT antibodies and quantitative real-time PCR (qRT-PCR) were performed using standard protocols. TPIT expression was completely absent (protein and mRNA) in PanNETs, pheochromocytomas, and all ACTH-negative NETs. In contrast, it was expressed in 16/32 LuNETs, although with lower levels than in PitNETs. No definite relationship was found between immunohistochemistry TPIT expression and NET grade or the presence of Cushing syndrome. This study further highlights the clinical and biological heterogeneity of extra-pituitary ACTH secretion and suggests that the differences between ACTH-secreting PanNETs and LuNETs may mirror distinct molecular mechanisms underlying POMC expression. Our results point towards the recognition of a real corticotroph-like phenotype of ACTH-producing LuNETs, that is not a feature of ACTH-producing PanNETs.

Renal neuroendocrine tumors: clinical and molecular pathology with an emphasis on frequent association with ectopic Cushing syndrome

Renal neuroendocrine tumors (RenNETs) are rare malignancies with largely unknown biology, hormone expression, and genetic abnormalities. This study aims to improve our understanding of the RenNETs with emphasis of functional, hormonal, and genetic features. Surgically resected RenNETs (N = 13) were retrieved, and immunohistochemistry and next-generation sequencing (NGS) were performed in all cases. In addition, all published RenNETs were systematically reviewed. Our cohort (4 men and 9 women, mean age 42, mean tumor size 7.6 cm) included 2 patients with Cushing syndrome (CS). WHO grade (23% G1, 54% G2, and 23% G3) and tumor progression did not correlate. CS-associated RenNETs (CS-RenNETs) showed a solid and eosinophilic histology and stained for ACTH, while the remaining non-functioning tumors had a trabecular pattern and expressed variably hormones somatostatin (91%), pancreatic polypeptide (63%), glucagon (54%), and serotonin (18%). The transcription factors ISL1 and SATB2 were expressed in all non-functioning, but not in CS-RenNETs. NGS revealed no pathogenic alterations or gene fusions. In the literature review (N = 194), 15 (8%) of the patients had hormonal syndromes, in which CS being the most frequent (7/15). Large tumor size and presence of metastasis were associated with shorter patients' survival (p < 0.01). RenNETs present as large tumors with metastases. CS-RenNETs differ through ACTH production and solid-eosinophilic histology from the non-functioning trabecular RenNETs that produce pancreas-related hormones and express ISL1 and SATB2. MEN1 or DAXX/ARTX abnormalities and fusion genes are not detected in RenNETs, indicating a distinct yet unknown molecular pathogenesis.

[Infectious pneumonia favored by paraneoplastic Cushing syndrome in a pulmonary carcinoid tumor]

INTRODUCTION

Ectopic Cushing's syndrome (CS) is a rare condition nevertheless well-known to endocrinologists. The pneumologist may be called upon to treat CS not only because bronchial carcinoid tumors are the most frequent source of ectopic ACTH secretion, but also due to the fact that the immunosuppression induced by hypercorticism favors lower respiratory tract infections.

CASE REPORT

We report the case of a female patient presenting with acute respiratory failure secondary to Enterobacter cloacae pneumonia exacerbated by SC. Further investigations confirmed ectopic ACTH secretion and revealed a right upper lobe pulmonary nodule. After appropriate antibiotic therapy, the patient received preoperative adrenolytic treatment. Management by right upper lobectomy resulted in the extraction of a 12mm tumor. Pathological analysis was consistent with the diagnosis of a typical carcinoid tumor. Immunohistochemistry confirmed ACTH secretion by the tumor. Even though the postoperative course showed CS regression, the patient developed adrenal insufficiency.

CONCLUSION

Ectopic CS induces immunosuppression, which aggravates lower respiratory tract infections. Search for a pulmonary neuroendocrine tumor should be systematic. Following control of the secretory syndrome by adrenolytic treatment, and if the diagnosis of carcinoid tumor is confirmed, surgical treatment is the preferred option.

Diagnostic, Prognostic, and Predictive Role of Ki67 Proliferative Index in Neuroendocrine and Endocrine Neoplasms: Past, Present, and Future

The introduction of Ki67 immunohistochemistry in the work-up of neuroendocrine neoplasms (NENs) has opened a new approach for their diagnosis and prognostic evaluation. Since the first demonstration of the prognostic role of Ki67 proliferative index in pancreatic NENs in 1996, several studies have been performed to explore its prognostic, diagnostic, and predictive role in other neuroendocrine and endocrine neoplasms. A large amount of information is now available and published results globally indicate that Ki67 proliferative index is useful to this scope, although some differences exist in relation to tumor site and type. In gut and pancreatic NENs, the Ki67 proliferative index has a well-documented and accepted diagnostic and prognostic role and its evaluation is mandatory in their diagnostic work-up. In the lung, the Ki67 index is recommended for the diagnosis of NENs on biopsy specimens, but its diagnostic role in surgical specimens still remains to be officially accepted, although its prognostic role is now well documented. In other organs, such as the pituitary, parathyroid, thyroid (follicular cell-derived neoplasms), and adrenal medulla, the Ki67 index does not play a diagnostic role and its prognostic value still remains a controversial issue. In medullary thyroid carcinoma, the Ki67 labelling index is used to define the tumor grade together with other morphological parameters, while in the adrenal cortical carcinoma, it is useful to select patients to treated with mitotane therapy. In the present review, the most important information on the diagnostic, prognostic, and predictive role of Ki67 proliferative index is presented discussing the current knowledge. In addition, technical issues related to the evaluation of Ki67 proliferative index and the future perspectives of the application of Ki67 immunostaining in endocrine and neuroendocrine neoplasms is discussed.

Ectopic adrenocorticotropic hormone-secreting carcinoid with solitary cryptococcosis in the lungs

BACKGROUND

Carcinoid tumors can on rare occasions ectopically produce adrenocorticotropic hormone (ACTH), causing Cushing's syndrome, and patients could become immunocompromised. Care must therefore be taken regarding infectious complications. In particular, ACTH-producing pulmonary carcinoid is not easy to diagnose by itself, and when combined with pulmonary nodules as infectious foci, each is very difficult to diagnose.

CASE

The patient was a 71-year-old woman with refractory diabetes. She showed clinical symptoms of Cushing's syndrome during treatment for diabetes and ectopic ACTH production was suspected based on biochemical and imaging tests. Nodules were identified in the left lung apex and lingual segment. Examination of resected nodules revealed that the nodule in the apex was pulmonary cryptococcosis, while the nodule in the lingual segment represented typical carcinoid. After surgery, clinical symptoms, laboratory findings, and diabetes all improved.

CONCLUSION

We present this very instructive case in terms of the difficulty of diagnosing ACTH-producing tumors, the possibility of infection complicating the immunodeficiency caused by ACTH-producing tumors, and the surgical strategy.

Ectopic Cushing's syndrome due to thymic neuroendocrine tumours: a systematic review

Knowledge of ectopic Cushing's syndrome (CS) due to thymic neuroendocrine tumours (NETs) comes from short series or single cases. Our aim is to perform a systematic review using PubMed, Embase, Scopus, Ovid Medline and Biosis Previews of all cases with ectopic CS due to thymic NETs reported in the last 40 years and describe one illustrative patient attended in our institution. Search of literature: From 162 patients, 58.6% were male and mean age was 34.6 ± 13.9 years-old. Median of symptoms until diagnosis was 6 [2-24] months and 62% had aggressive CS. Imaging was positive in 93.7% (chest X-ray), 97.8% (computed tomography), 80.7% (somatostatin receptor scintigraphy) and median tumour size was 47 [25-68.5] mm. At presentation, 18% had localized disease, 26.2% locally invasive and 55.7% advanced. Eighty-eight present underwent surgery and histological subtypes were atypical (46.7%), typical (30.4%) and carcinoma (21.7%). Tumour persisted or recurred in 70.1%, 63% received radiotherapy and 45.2% chemotherapy. Follow-up median was 26.6 [14.5-57.5] months and mortality was reported in 35.8% with median survival of 38 [19-60] months. MEN-1 mutation was referred in 3.1%. Comparatively, carcinomas had aggressive CS more frequently while atypical showed advanced disease more often. In conclusion, thymic NETs causing ectopic CS are presented as aggressive hypercortisolism in the middle aged population. The disease is commonly extended at diagnosis and persists or recurs after surgery in most patients with a short term high mortality.

Use of 18F-FDG PET/CT to Differentiate Ectopic Adrenocorticotropic Hormone-Secreting Lung Tumors From Tumor-Like Pulmonary Infections in Patients With Ectopic Cushing Syndrome

Background

Ectopic adrenocorticotropic hormone (ACTH)-secreting lung tumors represent the most common cause of ectopic Cushing syndrome (ECS). Pulmonary opportunistic infections are associated with ECS. The present study aimed to evaluate the usefulness of ¹⁸F-FDG PET/CT for differentiating ectopic ACTH-secreting lung tumors from tumor-like pulmonary infections in patients with ECS.

Methods

We retrospectively reviewed the imaging data of 24 patients with ECS who were suspected to have ACTH-secreting lung tumors and underwent ¹⁸F-FDG PET/CT between 2008 and 2019. Eleven patients with lung tumors and 4 with pulmonary infections also had additional somatostatin receptor imaging (^99mTc-HYNIC-TOC SPECT/CT or ⁶⁸Ga-DOTATATE PET/CT).

Results

In total, 18 patients had lung tumors and six had pulmonary infections. The primary source of ECS remained occult in the six patients with pulmonary infections. The maximum standardized uptake value (SUV_max) for pulmonary infections was significantly higher than that for tumors (P = 0.008). Receiver operating characteristic analysis revealed that a cut-off SUV_max of 4.95 helped in differentiating ACTH-secreting lung tumors from infections with 75% sensitivity and 94.4% specificity. For the 11 patients with ACTH-lung tumors, somatostatin receptor imaging (SRI) was positive in 6; while for the 4 with pulmonary infections, SRI was positive in 2. The sensitivity and specificity of somatostatin receptor imaging (SRI) for detecting ACTH-secreting lung tumor was 54.5% and 50%.

Conclusions

Our findings suggest that pulmonary infections exhibit significantly higher FDG uptake than ACTH-secreting lung tumors in ¹⁸F-FDG PET/CT. An SUV_max cut-off value of 4.95 may be useful for differentiating the two conditions. Our results also suggested that SRI may not be an effective tool for differentiating the two conditions given the relatively low specificity.

An ectopic Cushing's syndrome as a cause of severe refractory hypokalemia in the ICU

Background: Ectopic Cushing's syndrome is a very rare condition caused by an ACTH-secreting tumor outside the pituitary or adrenal glands, and the majority of these cases are encountered in the context of paraneoplastic syndromes. The ectopic source of ACTH secretion is not always obvious to detection and can be challenging. We report a rare case, in which a hidden ACTH-secreting carcinoid tumor of the lung caused a severe refractory hypokalemia, leading us to a race against time to locate the tumor.Case presentation: A 33-year-old young male was admitted to the ICU for the management of a severe hypokalemia, and complains from several months of depression, increased weight, disabling non-radiating dorsal lower back pain and refractory arterial hypertension. The physical examination immediately suggested a Cushing's syndrome. The 24-h cortisoluria confirmed hypercortisolism and the increased ACTH level was oriented towards ACTH-dependent Cushing's syndrome. Thereafter, a dexamethasone suppression test was negative, indicating in favor of ectopic ACTH secretion. The etiological assessment via imaging and isotopes revealed a solitary pulmonary nodule at the right lower lobe estimated at 18 mm, the resection and anatomopathological analysis of which led to the diagnosis of carcinoid pulmonary tumor, and resolved hypercortisolism and its complications.Conclusion: A delayed diagnosis of Cushing's syndrome result in a consequent morbi-mortality, mainly due to cardiovascular events. The optimal treatment for ectopic Cushing's syndrome is surgical resection, thus making the localization of the tumor a key element.

Pituitary neuroendocrine tumors: a model for neuroendocrine tumor classification

The classification of adenohypophysial neoplasms as "pituitary neuroendocrine tumors" (PitNETs) was proposed in 2017 to reflect their characteristics as epithelial neuroendocrine neoplasms with a spectrum of clinical behaviors ranging from small indolent lesions to large, locally invasive, unresectable tumors. Tumor growth and hormone hypersecretion cause significant morbidity and mortality in a subset of patients. The proposal was endorsed by a WHO working group that sought to provide a unified approach to neuroendocrine neoplasia in all body sites. We review the features that are characteristic of neuroendocrine cells, the epidemiology and prognosis of these tumors, as well as further refinements in terms used for other pituitary tumors to ensure consistency with the WHO framework. The intense study of PitNETs has provided information about the importance of cellular differentiation in tumor prognosis as a model for neuroendocrine tumors in different locations.

Morphologic and molecular classification of lung neuroendocrine neoplasms

Neuroendocrine neoplasms (NENs) of the lung encompass neuroendocrine tumors (NETs) composed of typical (TC) and atypical (AC) carcinoids and full-fledged carcinomas (NECs) inclusive of large cell neuroendocrine carcinoma (LCNEC) and small cell carcinoma (SCLC). NETs and NECs are thought to represent distinct and separate lesions with neither molecular overlap nor common developmental continuum. Two perspectives were addressed regarding the morphologic and molecular classification of lung NENs: (i) a supervised approach by browsing the traditional classification, the relevant gene alterations, and their clinical implications; and (ii) an unsupervised approach, by reappraising neoplasms according to risk factors and natural history of disease to construct an interpretation model relied on biological data. We herein emphasize lights and shadows of the current classification of lung NENs and provide an alternative outlook on these tumors focused on what we currently know about the biological determinants and the natural history of disease.

Glucocorticoid Receptor Antagonism Upregulates Somatostatin Receptor Subtype 2 Expression in ACTH-Producing Neuroendocrine Tumors: New Insight Based on the Selective Glucocorticoid Receptor Modulator Relacorilant

Somatostatin exhibits an inhibitory effect on pituitary hormone secretion, including inhibition of growth hormone and adrenocorticotropic hormone (ACTH), and it can have antisecretory and antitumor effects on neuroendocrine tumors (NETs) that express somatostatin receptors. Although the precise mechanism remains unclear, the finding that glucocorticoids downregulate somatostatin receptor subtype 2 (SSTR2) expression has been used to explain the lack of efficacy of traditional SSTR2-targeting analogs in patients with ACTH-secreting NETs. Glucocorticoid receptor (GR) antagonism with mifepristone has been shown to reverse the glucocorticoid-induced downregulation of SSTR2; however, the effects of GR modulation on SSTR2 expression in ACTH-secreting NETs, particularly corticotroph pituitary tumors, are not well known. The current study presents new insight from in vitro data using the highly selective GR modulator relacorilant, showing that GR modulation can overcome dexamethasone-induced suppression of SSTR2 in the murine At-T20 cell line. Additional data presented from clinical case observations in patients with ACTH-secreting NETs suggest that upregulation of SSTR2 via GR modulation may re-sensitize tumors to endogenous somatostatin and/or somatostatin analogs. Clinical, laboratory, and imaging findings from 4 patients [2 ACTH-secreting bronchial tumors and 2 ACTH-secreting pituitary tumors (Cushing disease)] who were treated with relacorilant as part of two clinical studies (NCT02804750 and NCT02762981) are described. In the patients with ectopic ACTH secretion, SSTR2-based imaging (Octreoscan and ⁶⁸Ga-DOTATATE positron emission tomography) performed before and after treatment with relacorilant showed increased radiotracer uptake by the tumor following treatment with relacorilant without change in tumor size at computed tomography. In the patients with Cushing disease who received relacorilant prior to scheduled pituitary surgery, magnetic resonance imaging after a 3-month course of relacorilant showed a reduction in tumor size. Based on these findings, we propose that GR modulation in patients with ACTH-secreting NETs upregulates previously suppressed SSTR2s, resulting in tumor-specific antisecretory and anti-proliferative effects. The effect of relacorilant on pituitary corticotroph tumors is being investigated in an ongoing phase 3 study (NCT03697109; EudraCT 2018-003096-35).

Neuroendocrine syndrome in bronchial carcinoid tumors

Pulmonary carcinoid tumors represent bronchopulmonary neuroendocrine neoplasms which might synthetize serotonin, histamine, bombesin or other types of hormones responsible for the development of a broad spectrum of signs and symptoms, known as carcinoid syndrome. Data of 98 patients submitted to surgery for bronchial carcinoid tumors in the Thoracic Surgery Clinic of the 'Marius Nasta' Institute of Pneumophtisiology between 2014 and 2018 were retrospectively reviewed. All patients were submitted to paraclinical tests, imagistic studies (computed tomography or magnetic resonance imaging), bronchoscopy and biopsy in order to have a positive diagnostic of pulmonary carcinoid. The most common clinical symptoms at the time of presentation were: Persistent cough followed by dyspnea and recurrent pulmonary infections. The main neuroendocrine syndromes found were Cushing and Carcinoid Syndrome. All patients were submitted to surgery with curative intent consisting of wedge resection (in 4 cases, 4.08%), lobectomy (in 79 cases, 80.61%), bilobectomy (in 5 cases, 5.1%) and pneumonectomy respectively (in 10 cases, 10.2%). In all cases neuroendocrine specific symptoms disappeared once the carcinoid tumor was removed. In conclusion, bronchial carcinoid tumors have a positive outcome in most cases. Specific neuroendocrine markers as well as neuroendocrine syndrome disappears once the tumor is removed.

Carcinoid Tumorlets Co-Existing with Chronic Pulmonary Inflammatory Processes: Imaging Findings and Histological Appearances

Background

Pulmonary carcinoid tumorlets (PCT) are incidental histologic or radiologic discoveries that are localized neuroendocrine tumors whose proliferation is associated with chronic pulmonary inflammatory processes. This study assessed the imaging findings and histological appearances of PCT co-existing with chronic pulmonary inflammatory processes.

Material/Methods

We performed a retrospective study of 14 patients with incidentally-found PCT with co-existing chronic pulmonary inflammatory processes who underwent preoperative X-rays and CT between 1 January 2003 and 31 December 2012. The clinical symptoms, X-rays, CT imaging findings, and histological appearances were retrospectively evaluated.

Results

Twelve women and 2 men were found to have PCT, with a mean age of 55.29±13.90 years (range 25–74 years) at diagnosis. Among these 14 patients, hemoptysis, cough, chest pain, expectoration, and chest tightness were found in 9 (64.3%), 5 (35.7%), 4 (28.6%), 3 (21.4%), and 1, respectively. For most patients, we could not find any small nodules on the X-ray or CT images. However, indirect imaging findings of bronchiectasis (85.7%, 12/14), atelectasis (57.1%, 8/14), inflammation (92.8%, 13/14), tuberculosis (7.1%, 1/14), and lung cancer (7.1%, 1/14) were found in all 14 patients.

Conclusions

PCT occurs most commonly in middle-aged women who have chronic pulmonary inflammatory processes such as bronchiectasis, atelectasis, and inflammation. Although there are no specific symptoms or direct imaging findings in these patients, our results showed that patients who have bronchiectasis, atelectasis, or recurrent pulmonary infection are at increased risk for PCT.