Definitive diagnosis of neuroendocrine tumors using fine-needle aspiration-puncture guided by endoscopic ultrasonography
Diagnóstico definitivo de los tumores neuroendocrinos (TNE) mediante PAAF ecodirigida por ultrasonografía endoscópica (USE)
Joan Gornals1,2,3, Modesto Varas3, Isabel Catalá1, Sandra Maisterra1, Carlos Pons1, Domingo Bargalló2, Teresa Serrano1 and Joan Fabregat1
1Department of Enchoendoscopy. Service of Digestive Diseases, Pathology, and Digestive and General Surgery. Hospital Universitario de Bellvitge. Hospitalet de Llobregat, Barcelona. Spain.
2Department of Echoendoscopy. Centro Médico Delfos. Barcelona, Spain.
3Centro Médico Teknon. Barcelona, Spain
ABSTRACT
Background: the detection and diagnosis of neuroendocrine tumors (NETs) is challenging. Endoscopic ultrasonography (EUS) has a significant role in the detection of NETs suspected from clinical manifestations or imaging techniques, as well as in their precise localization and cytological confirmation using EUS-Fine-needle aspiration-puncture (FNA).
Objective: to assess the usefulness and precision of EUS-FNAP in the differential diagnosis and confirmation of NETs, in a retrospective review of our experience.
Patients and methods: in a total of 55 patients with suspected NETs who underwent radial or sectorial EUS, 42 tumors were detected in 40 cases. EUS-FNA using a 22G needle was performed for 16 cases with suspected functional (hormonal disorders: 6 cases) and non-functional NETs (10 cases). Ki 67 or immunocytochemistry (ICC) testing was performed for all.
There was confirmation in 9 cases (5 female and 4 male) with a mean age of 51 years (range: 41-81 years).
All tumors were located in the pancreas except for one in the mediastinum and one in the rectum, with a mean size of 19 mm (range: 10-40 mm).
Results: there were no complications attributable to FNA. Sensitivity was 100% and both precision and PPV were 89%, as a false positive result suggested a diagnosis with NET during cytology that surgery finally revealed to be a pancreatic pseudopapillary solid tumor. ]]>
Conclusions: EUS-FNA with a 22G needle for NETs has high sensitivity and PPV at cytological confirmation with few complications.
Key words: Fine-needle aspiration-puncture (FNA) guided by endoscopic ultrasonography (EUS) or echoendoscopy, neuroendocrine tumors (NETs). Pancreatic endocrine tumors (PETs). Immunocytochemistry. Immunohistochemistry. Chromogranin. Synaptophysin. Cytokeratin 19. Vimentin. Ki 67. CD56.
RESUMEN
Introducción: la localización y diagnóstico de los tumores neuroendocrinos (TNE) es difícil. La ultrasonografía endoscópica (USE) tiene un papel significativo en la detección de TNE sospechados por la clínica u otras técnicas de imagen, así como en la localización exacta y confirmación citológica mediante USE-PAAF.
Objetivo: valorar la utilidad y precisión de la PAAF-USE en el diagnóstico diferencial y de confirmación de los TNE, en una revisión retrospectiva de la experiencia de nuestro grupo.
Pacientes y métodos: de un total de 55 enfermos con sospecha de TNE a los que se le practicó USE radial o sectorial, se detectaron 42 tumores en 40 casos. En 16 casos con sospecha de TNE funcionantes (trastornos hormonales: 6 casos) y no funcionantes (10 casos), se les practicó USE-PAAF con 22 G. En todos se efectuó Ki 67 o inmunocitoquímica (ICQ).
Hubo confirmación quirúrgica en 9 casos (5 M y 4 V), con una media de edad de 51 años (rango: 41-81 años).
Los tumores se localizaban todos en el páncreas, excepto uno en el mediastino y uno en el recto, con un tamaño medio de 19 mm (rango: 10-40 mm).
Resultados: no hubo complicaciones atribuibles a la PAAF. La sensibilidad fue del 100% (8/8), y la precisión y el VPP fue del 89% (8/9), ya que hubo un falso positivo que en el estudio citológico sugirió el diagnóstico de TNE pero que su resección quirúrgica confirmó el diagnóstico de tumor sólido seudopapilar del páncreas.
Conclusiones: la USE-PAAF con 22 G de los TNE posee una alta sensibilidad y VPP en la confirmación citológica de estos pacientes, con muy escasas complicaciones.
Introduction
The preoperative diagnosis and precise localization of neuroendocrine tumors (NETs), particularly pancreatic NETs (PNETs), is challenging, and vital for a definitive cure of patients (1). For non-functioning cases, confirmation by histology is most necessary because of potential differential diagnoses. PNETs share histological properties with carcinoids: both are considered to derive from the diffuse endocrine cell system; they unusually exhibit mitotic features (assessable using the Ki-67 -index); they usually show electrodense granules that contain hormones and various peptides, chromogranins (A, B, C), neuron-specific enolase (NSE), and synaptophysin (2,3).
PNETs are clinically classified as functional (Zollinger-Ellison syndrome, etc.) and non-functional. The clinical diagnosis of functional PNETs is relatively straightforward.
Most are benign (no metastases) and small, and may be associated with multiple endocrine neoplasia (MEN). Non-functional tumors are most common among PNETs, and have a high incidence of metastatic disease.
Their precise localization in the pancreas is difficult. Echoendoscopy or endoscopic ultrasonography (EUS) is a rather recently introduced diagnostic technique, and may diagnose tumors smaller than 1 cm (up to 3 mm) in the pancreas head and body with a sensitivity above 85% (93% in the larger series), whereas those in the tail are harder to assess (1).
EUS allows fine-needle aspiration-puncture (FNA) under ultrasound (US) guidance (4), and the collection of material for cytology and histology with a yield nearing 90%. In addition, immunocytochemistry (ICC) and immunohistochemistry (IHC) tests may be performed on obtained samples for chromogranin (C-A), synaptophysin, cytokeratin 19, and various hormones or peptides, with diagnoses that may reach 100% for cystic PNETs (5).
A recent classification proposed by WHO (2) assigned three categories to NETs: well-differentiated tumor, well-differentiated carcinoma, and poorly differentiated carcinoma based on histology, size (limit: 2 cm), and proliferation index (Ki-67 = 2%).
A TNM (tumor, node, and metastasis) classification has also been suggested for PNETs based on the WHO classification (3).
]]>Objective
To assess the usefulness and precision of EUS-FNA in the differential and confirmatory diagnosis of NETs using a retrospective review of our team's experience.
Patients and method
For a total of 55 patients with suspected PNETs who underwent radial or sectorial EUS, 42 tumors were identified in 40 patients. Inclusion criteria for EUS-FNA: patients with presumed NET diagnosis with EUS, uncertain or non-functional.
For 16 cases (8 women and 8 men with a mean age of 56, range: 41-92 years with suspected functional (6 cases) and non-functional (10 cases) tumors, none of them cystic, EUS-FNA was performed using a 22 G needle (Echotip Ultra, Cook Medical) with conventional technique. All cases underwent Ki67 testing or immunocytochemistry for chromogranin, synaptophysin, and various hormones or peptides.
There was surgical confirmation (the gold standard) in 9 patients; in the remaining cases imaging techniques and 12-month follow-up (the gold standard) were used to reach a definitive diagnosis.
From all 16 patients 9 (5 women, 4 men) were selected with a mean age of 51 years (range: 41-81 years).
All tumors were in the pancreas, and one was in the mediastinum and one in the rectum, with a mean size of 19 mm (range: 10 to 40 mm) (Table I).
]]> Regarding pancreatic tumors, three were in the head, two in the tail, and two in the body. Only two patients had metastases.All examinations (EUS-FNA) were performed after collecting an informed consent, with prior coagulation testing, and using sedation (propofol) by an anesthetist.
A cytologist was in all cases present in the examination room where EUS-FNA procedures were carried out.
Diagnostic precision (P), sensitivity (S), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) were all analyzed using standard formulas.
Results
There were no EUS-FNA-related complications (hemorrhage and perforation).
In the total series (16 cases) S was 100% with a Sp of 67%, P and PPV of 93 and 92%, respectively.
In patients with surgical confirmation (9 cases) sensitivity (S) was 100%, and precision (P) and PPV were 89%, as cytology yielded a false positive result that was eventually diagnosed as a solid pancreatic pseudopapillary tumor following surgical excision and tail pancreatectomy plus IHC.
]]> Discussion
EUS-FNA has been performed for PNETs for slightly over 10 years now. In earlier works both sensitivity and precision were low, with a specificity of 100% (6); however, they gradually increased, and sensitivity reached about 90% (94% in the most extensive series in the literature) (6-22) (Table II).
Our findings are consistent with those in the literature (S: 100%).
Typical EUS findings include homogeneous pancreatic nodules or lesions that are hypoechogenic, solid, hypervascular, and encapsulated with well-delimited borders (1,22,29), even non-functional ones (most of them) (22). NFPETs show the greatest sizes and are more advanced (Fig. 1).
The use of ICC techniques (chromogranin, synaptophysin, etc.) (cytokeratin 19) (23) considerably improves sensitivity on cytology material (Fig. 2).
The Ki 67 index (24-26) and microsatellite instability have also been assessed in samples (27,28) to establish the benign or malignant nature of tumors, and hence their prognosis.
Algorithms are similar for PNETs and pancreatic cancers (PCs) (4,29) (Fig. 3).
When a tumor is resectable according to computed tomography plus EUS, and both clinical and morphological features are consistent, laparoscopic or open surgery may be readily performed. For uncertain or non-functioning tumors EUS-FNA may be used to confirm diagnostic suspicion.
Sometimes a histological differential diagnosis is -difficult between pancreatic endocrine tumors, solid pseudopapillary tumor, acinar cell carcinomas, mucinous tumors, and lymphoma/plasmocytoma. In recent years various cases of solid pseudopapillary tumor have been described where ICC reached the right diagnosis on EUS-FNA-collected samples (30-33): most were vimentin+ and cytokeratin+, whereas chomogranin and NSE were negative (they may be focally positive though) (34).
]]> In this multicenter study in 28 patients with pseudopapillary tumors (34) a preoperative diagnosis was reached for 21 cases (75%); vimentin, alfa1-antitrypsin, CD10, and beta-catenin were positive in all cases, whereas chromogranin was positive in just 1/20 (5%) and synaptophysin in 10/17 (59%); however, the best marker to tell endocrine -tumors from solid pseudopapillary tumors was E-cadherin/B-catenin/CD10 according to a recent study (35).In our case with a solid pancreatic pseudopapillary tumor IHC was key for a definitive diagnosis. False positive results have been described in other series (12,18).
A recent Japanese study (36) reviewed 455 pancreatic FNA procedures: 28 were rare pancreatic tumors (no ductal adenocarcinomas). EUS-FNA with cytology, cell-block, and immunocytochemistry correctly diagnosed tumor type in 19 patients 19 (68%).
In differentiating benign from malignant tumors it had a sensitivity of 69%, a specificity of 100%, a PPV of 100%, a NPV of 79%, and a precision of 86%. None of the three malignant pancreatic endocrine tumors was diagnosed as such. EUS-FNA changed the presumed diag-nosis in 11 cases (39%).
Four cases have been recently reported (37) where small (8-16 mm), non-functioning pancreatic endocrine tumors were found together with intraductal papillary mucinous neoplasms. PNETs remained undetected by common imaging techniques (CT and MRI); 3/4 were diag-nosed using EUS, and only 1/3 using EUS-FNA.
To conclude, ICC on cytology samples collected by EUS-FNA is key for a definitive diagnosis of PNETs. Our study (S: 100%) (PPV: 89%) confirmed the findings in the literature (mean sensitivity of 94%, mean specificity of 95%) (Table II).
Notwithstanding, the diagnostic panel is increasingly greater, and novel markers emerge including SERPINB8 (38), which is as sensitive as C-A and synaptophysin, or CDX-2, PDX-1, NESP-55 and TTF-1, which may help in the differential diagnosis between gastrointestinal and pulmonary carcinoids, and pancreatic endocrine tumors (39), with CK 19 being an independent prognostic factor for PNETs, particularly non-insulinomas according to a recent review (40). However, chromogranin and synaptophysin remain the key markers since many years ago (43) to this day (44).
Thus, believe that ICC is key for a definitive diagnosis of NETs (45), a statement not fully shared by other teams (44).
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Correspondence:
M. Varas Lorenzo.
C. M. Teknon.
C/ Marquesa de Vilallonga 12.
08017 Barcelona, Spain.
e-mail: varas@dr.teknon.es
Received: 19-07-10.
Accepted: 30-09-10.