Definition/General
Introduction:
Gastric carcinoid tumors are neuroendocrine neoplasms arising from enterochromaffin-like (ECL) cells
They represent 1-2% of gastric tumors
Three distinct types based on pathogenesis
Cytological diagnosis requires recognition of neuroendocrine features.
Origin:
Arise from ECL cells in gastric mucosa
Type I: Associated with chronic atrophic gastritis
Type II: Associated with MEN-1, Zollinger-Ellison syndrome
Type III: Sporadic, most aggressive.
Classification:
WHO 2019 classification: Grade 1 (G1), Grade 2 (G2), Grade 3 (G3)
Type I (70%): Hypergastrinemia, multiple small tumors
Type II (5%): MEN-1 associated
Type III (25%): Sporadic, large solitary.
Epidemiology:
Peak age 50-60 years
Female predominance (Type I)
Equal gender distribution (Type III)
Increasing incidence
Associated with PPI use.
Clinical Features
Presentation:
Often asymptomatic
Dyspepsia
Abdominal pain
GI bleeding
Carcinoid syndrome (rare)
Incidental finding.
Symptoms:
Epigastric discomfort
Nausea
Early satiety
Anemia
Flushing (rare)
Diarrhea (rare).
Risk Factors:
Chronic atrophic gastritis
H
pylori infection
Pernicious anemia
MEN-1 syndrome
Long-term PPI use.
Screening:
Chromogranin A levels
Gastrin levels
Endoscopic surveillance
MEN-1 screening.
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Gross Description
Appearance:
Small polypoid lesions (Type I, II)
Large solitary mass (Type III)
Yellow-brown color
Smooth surface
Multiple lesions (Type I).
Characteristics:
Firm consistency
Well-circumscribed
Homogeneous cut surface
No necrosis (G1, G2)
Central necrosis (G3).
Size Location:
Fundus and body (Type I, II)
Any location (Type III)
Size <1 cm (Type I)
Size >3 cm (Type III).
Multifocality:
Multiple tumors (Type I, II)
Single tumor (Type III)
Synchronous lesions
Metachronous development.
Microscopic Description
Histological Features:
Uniform round cells
"Salt and pepper" chromatin
Moderate cytoplasm
Organoid pattern
Trabecular arrangement
Nested pattern.
Cellular Characteristics:
Round to oval nuclei
Finely granular chromatin
Inconspicuous nucleoli
Eosinophilic cytoplasm
Cellular uniformity
Neuroendocrine granules.
Architectural Patterns:
Organoid nests
Trabecular cords
Rosette formation
Solid sheets
Ribbon pattern
Perivascular arrangement.
Grading Criteria:
Grade 1: <2 mitoses/10 HPF, Ki-67 <3%
Grade 2: 2-20 mitoses/10 HPF, Ki-67 3-20%
Grade 3: >20 mitoses/10 HPF, Ki-67 >20%.
Immunohistochemistry
Positive Markers:
Chromogranin A
Synaptophysin
CD56
Neuron-specific enolase
Somatostatin receptor 2
Ki-67 (grading).
Negative Markers:
Cytokeratins (usually)
TTF-1
CDX2
Calcitonin
Insulin.
Diagnostic Utility:
Confirms neuroendocrine differentiation
Grading assessment
Differential diagnosis
Therapeutic targeting.
Molecular Subtypes:
Type I: Well-differentiated
Type II: Well-differentiated
Type III: Variable grade.
Molecular/Genetic
Genetic Mutations:
MEN1 mutations (Type II)
TP53 mutations (high-grade)
RB1 mutations
ATRX mutations
DAXX mutations.
Molecular Markers:
Chromogranin A
Somatostatin receptors
mTOR pathway
Notch signaling.
Prognostic Significance:
Grade most important
Size and invasion
Type classification
Lymph node status.
Therapeutic Targets:
Somatostatin analogs
mTOR inhibitors
PRRT
Chemotherapy (high-grade).
Differential Diagnosis
Similar Entities:
Adenocarcinoma
Lymphoma
Stromal tumors
Metastatic NET
Reactive changes.
Distinguishing Features:
NET: Neuroendocrine markers positive
Adenocarcinoma: Glandular features
Lymphoma: Hematopoietic markers.
Diagnostic Challenges:
Small biopsy specimens
Crush artifacts
Grade assessment
Type classification.
Rare Variants:
Mixed adenoneuroendocrine carcinoma
Large cell neuroendocrine carcinoma
Small cell carcinoma.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
Gastric cytology, adequate for evaluation
Diagnosis
Neuroendocrine tumor (Carcinoid)
Neuroendocrine Features
Uniform cells with [salt and pepper chromatin] and [organoid pattern]
Grading
Grade: [G1/G2/G3] based on mitotic count and Ki-67
Type Classification
Type: [I/II/III] gastric NET
Special Studies
Neuroendocrine markers: [Chromogranin A+, Synaptophysin+]
Ki-67 index: [percentage]
Final Diagnosis
Gastric cytology: Neuroendocrine tumor, Grade [1/2/3]