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Q1 · Infectious Esophagitis · HSV Histology
A 35-year-old man with HIV (CD4 100 cells/µL) presents with severe dysphagia and odynophagia. Endoscopy reveals multiple shallow ulcers with a herpetic appearance in the mid-esophagus. Biopsy shows intranuclear viral inclusions within squamous epithelial cells at the ulcer margin, with characteristic multinucleated giant cells. Which histologic pattern best describes these viral inclusions?
AMolding, Multinucleation, Margination in squamous cells at ulcer edge
BOwls-eye inclusions in endothelial cells at ulcer base
CPseudohyphae in surface exudate on GMS stain
DPerivascular lymphocytic infiltration with no inclusion bodies
EGranulation tissue with fibrinopurulent exudate
Correct: A — Molding, Multinucleation, Margination in squamous cells at ulcer edge
HSV esophagitis causes shallow herpetic ulcers with characteristic viral cytopathic changes in squamous epithelial cells at the ulcer margin. The classic histologic pattern is the "3 M's": Molding, Multinucleation, Margination — all features of viral inclusions in squamous nuclei. Ground-glass intranuclear inclusions and multinucleated giant cells are hallmarks.
B— Owls-eye inclusions are characteristic of CMV (in endothelial cells/fibroblasts at ulcer base, not squamous margin).
C— Pseudohyphae indicate Candida esophagitis, not HSV.
D, E— Not specific to HSV esophagitis.
Q2 · Infectious Esophagitis · CMV Inclusions
A 55-year-old organ transplant recipient (post-kidney transplant, day 180) develops severe odynophagia with a single large deep esophageal ulcer on endoscopy. Biopsy shows large nuclear and cytoplasmic inclusions within endothelial cells and fibroblasts at the base of the ulcer. Which organism is most likely responsible?
AHerpes simplex virus (HSV)
BCytomegalovirus (CMV) — owls-eye inclusions in endothelial/fibroblasts at ulcer base
CCandida albicans
DHelicobacter pylori
EAchalasia (mechanical obstruction)
Correct: B — CMV with owls-eye inclusions in endothelial cells at ulcer base
CMV esophagitis typically presents with large, deep ulcers (unlike shallow HSV ulcers) in immunosuppressed patients (transplant, AIDS with CD4 <50). The key histologic distinction is large nuclear and cytoplasmic inclusions in endothelial cells and fibroblasts AT THE ULCER BASE (not in squamous cells at margin as in HSV). These inclusions have the characteristic owls-eye appearance.
A— HSV causes shallow ulcers with 3-M pattern in squamous cells at margin.
C— Candida causes white plaques, not deep ulcers with endothelial cell inclusions.
D, E— Not infectious esophagitis causes.
Q3 · Infectious Esophagitis · Candida
A 42-year-old man with newly diagnosed HIV presents with odynophagia and white plaques in the esophagus on endoscopy. He also has oral thrush. Which of the following best describes the histologic findings expected on biopsy?
AIntranuclear multinucleated giant cells
BOwls-eye intracellular inclusions
CPseudohyphae and yeast on GMS stain within fibrinopurulent exudate
DSquamous cell carcinoma with keratinization
EColumnar metaplasia with goblet cells
Correct: C — Pseudohyphae and yeast on GMS stain
Candida esophagitis is the most common fungal esophagitis, especially in diabetic and immunosuppressed patients. Histologically, you see pseudohyphae and yeast organisms in tissue on GMS stain, often within a fibrinopurulent exudate. The characteristic endoscopic appearance is yellow-white plaques that scrape off.
A, B— Viral inclusion patterns; not seen in Candida.
D, E— Not Candida histology.
Q4 · GERD & Barrett's Esophagus · Precancer Risk
A 58-year-old man with long-standing GERD (20+ years) undergoes endoscopy for heartburn and dysphagia. The endoscopist notes irregular "salmon-tongues" of reddish mucosa extending above the gastroesophageal junction. Biopsy shows columnar epithelium with specialized intestinal-type mucosa containing goblet cells. What is the highest-yield Step 1 concept about this diagnosis?
AThe patient has a benign condition with no cancer risk and requires no surveillance
BBarrett's esophagus (intestinal metaplasia with goblet cells) is precancerous; progresses to adenocarcinoma; requires surveillance endoscopy
CThe squamous epithelium will regenerate with PPIs alone and no metaplasia will occur
DThis is esophageal squamous cell carcinoma requiring chemotherapy
EH. pylori is the primary cause and eradication reverses the condition
Correct: B — Barrett's esophagus is a precancerous precursor
Barrett's esophagus occurs in ~10% of patients with symptomatic GERD. It represents metaplasia of the normal squamous epithelium to columnar epithelium WITH GOBLET CELLS (intestinal metaplasia). This is a precancerous lesion — the single most important risk factor for esophageal adenocarcinoma. Dysplasia develops in the metaplastic tissue and may progress to adenocarcinoma. Patients require chronic surveillance endoscopy.
A— Barrett's IS precancerous.
C— Once metaplasia develops, it does not reverse.
D— This is adenocarcinoma risk, not current SCC.
E— GERD (not H. pylori) causes Barrett's esophagus.
Q5 · Esophageal SCC · Risk Factors & Location
A 65-year-old man with a 40-year history of heavy smoking and alcohol use presents with progressive dysphagia and weight loss. Endoscopy reveals an ulcerating lesion in the mid-esophagus with raised, irregular margins and submucosal infiltration. Biopsy shows squamous cell carcinoma with keratinization. Which is the most likely location for this tumor?
ADistal esophagus at the gastroesophageal junction
BMiddle third of esophagus (associated with smoking, alcohol, achalasia)
CUpper esophagus (cervical region)
DDiffuse throughout entire esophagus
ELower esophageal sphincter only
Correct: B — Middle third of esophagus
Esophageal SCC is most common in the middle third of the esophagus and is strongly associated with smoking, alcohol, and achalasia. The ulcerating type with overhanging margins is classic. SCC represents the majority of esophageal malignancies globally. Prognosis is poor (<10% 5-year survival) due to late diagnosis.
A— Distal esophagus/GE junction is the location for adenocarcinoma (associated with GERD/Barrett's), not SCC.
C, D, E— Not typical locations for esophageal SCC.
Q6 · Acute Gastritis · NSAID Mechanism
A 72-year-old woman taking ibuprofen daily for arthritis develops acute epigastric pain and hematemesis. She has melena and a drop in hemoglobin. Endoscopy shows acute hemorrhagic gastritis in the body of the stomach with multiple erosions. Which mechanism best explains NSAID-induced gastric injury?
AIncreased gastric acid secretion via G-cell stimulation
BInhibition of protective prostaglandins (COX inhibition) → reduced mucus, ↓HCO3 secretion, ↓ blood flow
CDirect toxic effect from H. pylori colonization
DAutoimmune destruction of parietal cells
EStress-induced Cushing ulcer from hypergastrinemia
Correct: B — COX inhibition → reduced mucosal protection
NSAIDs are a leading cause of acute gastritis and erosions/ulcers. They work by inhibiting COX enzymes, which blocks protective prostaglandin synthesis. Prostaglandins maintain mucosal blood flow, mucus secretion, and HCO3 secretion. Without them, the stomach loses its defense against acid and pepsin, leading to acute injury. This is a decrease in mucosal PROTECTION, not an increase in acid.
A— NSAIDs do not increase acid secretion.
C, D, E— Not mechanisms of NSAID gastritis.
Q7 · Gastric Pathology · Erosion vs. Ulcer
A pathologist examines gastric biopsies from two patients. Patient A shows a focal defect limited to the mucosa (not extending through the muscularis mucosae). Patient B shows a focal defect that penetrates the full thickness of the mucosa, extends into the submucosa, and involves the muscularis propria. Which histologic distinction best separates erosion from ulcer?
AErosion is larger; ulcer is smaller
BErosion has raised edges; ulcer has flat edges
CErosion is partial mucosal loss; ulcer is full-thickness mucosal defect extending into submucosa/muscularis
DErosion is from H. pylori; ulcer is from NSAIDs
EErosion leads to scarring; ulcer does not
Correct: C — Erosion = partial loss; Ulcer = full-thickness through submucosa/muscularis
This is a fundamental pathologic distinction:
Erosion = partial focal loss of mucosa; does NOT extend through muscularis mucosae; can heal without scarring
Ulcer = focal area of full-thickness destruction that extends into submucosa and may involve muscularis propria; can perforate; heals with scarring (4-layer: exudate, necrosis, granulation, scar)
A— Size alone does not distinguish them.
B— Peptic ulcers have flat sharp edges (not raised).
D— Both H. pylori and NSAIDs can cause erosions and ulcers.
E— Ulcers scar; erosions typically do not.
Q8 · H. pylori vs. Autoimmune Gastritis · Location
A 45-year-old man with chronic dyspepsia has a gastric biopsy showing chronic inflammation with neutrophils in the antrum. H. pylori organisms are identified on Warthin-Starry stain. Which statement best characterizes H. pylori-associated chronic gastritis?
AGastritis is limited to the fundus and body (antrum-sparing)
BH. pylori typically colonizes the antrum initially; can progress to pangastritis with atrophy and intestinal metaplasia
CSerology shows antibodies to intrinsic factor and parietal cell H⁺/K⁺-ATPase
DLeads to pernicious anemia and ECL cell hyperplasia
EAssociated with elevated gastrin and increased acid production
Correct: B — H. pylori antral gastritis; can progress to pangastritis
H. pylori is found in the antral mucosa on histology (Warthin-Starry stain shows spiral bacteria in surface mucus). Initially causes antral gastritis, but can progress to pangastritis (involving fundus and body as well), leading to atrophy and intestinal metaplasia with increased gastric cancer and MALT lymphoma risk.
A— Autoimmune gastritis is antrum-sparing; H. pylori is antral.
C, D, E— These are features of autoimmune gastritis (parietal cell antibodies, pernicious anemia, ECL hyperplasia), NOT H. pylori.
Q9 · PUD · Duodenal vs. Gastric Ulcer Pain Pattern
A 38-year-old man with a positive H. pylori test presents with epigastric pain that awakens him at 2 AM and is relieved 30 minutes after eating breakfast or taking antacids. Which type of peptic ulcer is most consistent with this pain pattern?
AGastric ulcer (pain worse with eating)
BDuodenal ulcer (pain relieved by food/antacids; nocturnal awakening classic)
CStress ulcer (acute onset post-trauma)
DZollinger-Ellison syndrome ulcer (refractory to standard therapy)
EGERD-related ulcer (burning substernal pain)
Correct: B — Duodenal ulcer with classic nocturnal pain pattern
Duodenal ulcers have a characteristic pain pattern:
• Pain relieved by food or antacids (buffer acid)
• Nocturnal awakening (acid secretion peaks at night)
• More related to hyperacidity + H. pylori
Gastric ulcers have a different pattern:
• Pain WORSENED by eating (food stimulates acid)
• More related to mucosal weakness + NSAIDs
C, D, E— Not consistent with this pain pattern.
Q10 · PUD Treatment · H. pylori Triple Therapy
A 52-year-old woman with H. pylori-positive duodenal ulcer is prescribed omeprazole (PPI), amoxicillin, and clarithromycin for 14 days. Which best describes the mechanism by which this therapy heals the ulcer and prevents recurrence?
AOmeprazole alone neutralizes existing acid in the duodenum
BTriple therapy eradicates H. pylori (bacteria are removed) + PPI reduces acid secretion to allow healing
CAntibiotics strengthen the mucosal barrier to acid
DPPIs permanently destroy parietal cells to stop acid production forever
EAmoxicillin and clarithromycin repair the ulcer by stimulating epithelial regrowth
Correct: B — H. pylori eradication + acid suppression
Triple therapy (PPI + 2 antibiotics) is the cornerstone of H. pylori-positive PUD treatment. The antibiotics eradicate the bacteria (addressing the root cause), while the PPI reduces acid secretion to allow mucosal healing. H. pylori eradication is curative — the ulcer heals and does not recur (unlike the chronic relapsing course before antibiotics were available).
A— Antacids neutralize; PPIs suppress synthesis.
C, D, E— Incorrect mechanisms of action.
Q11 · Precancerous Lesions · Atrophic Gastritis & Metaplasia
A 62-year-old woman with long-standing H. pylori infection (untreated for 30 years) develops chronic atrophic gastritis with intestinal metaplasia (goblet cells in gastric glands) on biopsy. Which best describes the significance of this finding?
AIntestinal metaplasia is a benign finding with no cancer risk
BIntestinal metaplasia is a precancerous condition associated with increased gastric adenocarcinoma risk
CThis lesion is reversible with H. pylori eradication alone
DGastric ulcer is the immediate next step in progression
EMALT lymphoma will definitely develop within 5 years
Correct: B — Intestinal metaplasia is precancerous
Intestinal metaplasia (replacement of gastric glands with goblet cells resembling intestinal mucosa) is a precancerous condition in chronic atrophic gastritis. It is associated with gastric carcinoma at the population, patient, and topographic level. Similar to Barrett's esophagus, intestinal metaplasia represents a field change that increases adenocarcinoma risk.
A— Intestinal metaplasia IS associated with cancer risk.
C— Once metaplasia develops, it does not fully reverse.
D, E— Ulcer is not the immediate next step; MALT lymphoma is not certain.
Q12 · Gastric Cancer · Diffuse Type & Signet Ring Cells
A 42-year-old woman presents with weight loss and early satiety. Endoscopy shows thickening and rigidity of the entire gastric wall without a discrete mass ("leather bottle stomach"). Biopsy reveals individual cells with central mucous droplets and peripherally displaced nuclei diffusely infiltrating the gastric wall. Which histologic feature and Lauren classification type is this?
AIntestinal type with gland-forming adenocarcinoma; associated with intestinal metaplasia precursor
BDiffuse type with signet ring cells; linitis plastica appearance; occurs in young patients; NOT associated with intestinal metaplasia
CMixed adenocarcinoma with mucinous and squamous differentiation
DSmall-cell carcinoma (neuroendocrine)
ELymphoma with CD20+ B-cell phenotype
Correct: B — Diffuse type with signet ring cells & linitis plastica
The diffuse (or infiltrative) type of gastric carcinoma is characterized by:
• Individual poorly differentiated cells spreading diffusely through the wall
• Signet ring cell morphology — central mucous droplet, displaced nucleus like a signet ring
• Linitis plastica ("leather bottle stomach") — stomach becomes rigid, non-distensible
• Occurs in young patients
• NOT strongly associated with intestinal metaplasia precursor (unlike intestinal type)
• Uniform worldwide distribution
• Poor prognosis
A— Intestinal type has gland formation and goblet cells, with intestinal metaplasia precursor.
C, D, E— Not diffuse gastric adenocarcinoma.
Q13 · GIST · c-KIT Tyrosine Kinase & Imatinib
A 55-year-old man presents with GI bleeding and is found to have a submucosal mass in the stomach on endoscopy. Biopsy shows spindle cells with c-KIT immunohistochemical staining positive. What is the most likely diagnosis and treatment?
ASmooth muscle leiomyosarcoma; treat with chemotherapy only
BGIST (gastrointestinal stromal tumor) with c-KIT mutation; treat with imatinib (tyrosine kinase inhibitor)
CLymphoma with CD20 expression; treat with rituximab
DAdenocarcinoma with signet ring cells; treat with 5-FU
ECarcinoid tumor; treat with octreotide
Correct: B — GIST with c-KIT mutation; treat with imatinib
GISTs are mesenchymal tumors of the GI tract, most commonly in the stomach. Key features:
• c-KIT positive on immunohistochemistry (CD117+)
• Associated with c-KIT tyrosine kinase gain-of-function mutations
• Spindle cell morphology
• Treatment: Imatinib (Gleevec) — a c-KIT tyrosine kinase inhibitor
• Highly effective even in metastatic disease
A— Leiomyosarcoma is c-KIT negative.
C, D, E— Different diagnoses with different markers and treatments.
Q14 · MALT Lymphoma · H. pylori Association
A 50-year-old woman is found to have gastric MALT lymphoma (mucosa-associated lymphoid tissue) on biopsy. H. pylori is identified in gastric tissue. Which statement best describes the relationship between H. pylori and MALT lymphoma?
AH. pylori is unrelated to MALT lymphoma; it is a sporadic malignancy
BH. pylori drives MALT lymphoma development; eradication of H. pylori often leads to lymphoma regression
CMALT lymphoma is unresponsive to any treatment
DNSAIDs cause MALT lymphoma, not H. pylori
EChemotherapy is immediately required; H. pylori eradication is not effective
Correct: B — H. pylori drives MALT lymphoma; eradication causes regression
MALT lymphoma (extranodal marginal zone B-cell lymphoma) is strongly associated with H. pylori infection. The bacterium drives chronic antigenic stimulation, leading to malignant transformation of gastric MALT. H. pylori eradication with triple therapy often leads to complete regression of MALT lymphoma — this is one of the few examples in oncology where treating an infection cures a malignancy.
A— H. pylori is a key driver, not unrelated.
C, E— MALT lymphoma IS responsive to H. pylori eradication.
D— H. pylori (not NSAIDs) is the primary association.
Q15 · H. pylori Diagnosis · Urease Breath Test
A 48-year-old man with peptic ulcer disease undergoes testing for H. pylori. He is given oral labeled urea (C13 or C14) and breath samples are collected before and after ingestion. The urease enzyme from H. pylori breaks down the labeled urea, producing labeled CO2 that is absorbed and exhaled. Which diagnostic method is this?
ASerology (antibody detection against H. pylori)
BUrease breath test — detects H. pylori urease enzyme; non-invasive; highly sensitive and specific
CGastric biopsy with histologic examination only
DStool antigen detection (ELISA)
ECulture on chocolate agar medium
Correct: B — Urease breath test
The urease breath test (UBT) is a non-invasive, highly sensitive and specific test for H. pylori infection. It exploits the fact that H. pylori produces urease enzyme, which breaks down urea to ammonia and CO2. When the patient ingests labeled urea (C13 or C14), the labeled CO2 is produced by H. pylori, absorbed into blood, and exhaled in breath. Detection of labeled CO2 in breath samples confirms infection.
A— Serology detects antibodies; does not reflect current infection (antibodies persist).
C— Biopsy is invasive (requires endoscopy); can use Warthin-Starry or immunostain.
D— Stool antigen test exists but is less sensitive than UBT.
E— Culture is difficult; H. pylori is fastidious.
Q16 · H. pylori Histology · Warthin-Starry Stain
A gastric biopsy from a patient with chronic gastritis is processed with Warthin-Starry silver stain. The pathologist identifies spiral-shaped, darkly stained bacteria within the surface mucus layer and gastric pits of the antrum. Which organism is this, and what is its morphology?
ACandida albicans — rod-shaped with pseudohyphae
BHelicobacter pylori — spiral-shaped (gram-negative bacillus); requires urease enzyme for colonization
CVibrio cholerae — comma-shaped curved rod
DClostridium difficile — gram-positive rod with spores
ETreponema pallidum — very thin spirochete (not visible on standard stains)
Correct: B — H. pylori spiral-shaped on Warthin-Starry stain
H. pylori is a gram-negative, microaerophilic bacterium with a spiral (S or comma) shape characteristic of curved gram-negative rods. On Warthin-Starry silver stain, it appears as darkly stained spiral organisms in the antral surface mucus and gastric pits. The organism requires urease enzyme to survive in the acidic stomach (urease produces ammonia, neutralizing acid).
A— Candida is fungal, not bacterial; forms pseudohyphae.
C— V. cholerae is curved but associated with diarrhea, not gastritis.
D— C. difficile is gram-positive.
E— T. pallidum is a spirochete but causes syphilis, not gastritis.
Q17 · Esophageal Adenocarcinoma · Barrett's Precursor
A 60-year-old man with a 15-year history of GERD undergoes surveillance endoscopy for known Barrett's esophagus. The endoscopist notes nodular mucosa and performs targeted biopsies. Histology shows back-to-back glandular adenocarcinoma with mucin production and extensive submucosal invasion. What is the most important risk factor that led to this cancer?
ASmoking and alcohol use
BChronic GERD → Barrett's esophagus (intestinal metaplasia with goblet cells) → dysplasia → adenocarcinoma
CH. pylori infection causing chronic esophagitis
DAchalasia and mechanical obstruction
ENSAIDs causing chronic ulceration
Correct: B — GERD → Barrett's → dysplasia → adenocarcinoma
Esophageal adenocarcinoma arises almost exclusively in patients with Barrett's esophagus. The progression is:
GERD → reflux damage → intestinal metaplasia (Barrett's with goblet cells) → low-grade dysplasia → high-grade dysplasia → adenocarcinoma
Most esophageal adenocarcinomas occur in the distal esophagus/GE junction and are associated with GERD, obesity, and Barrett's esophagus — NOT smoking/alcohol (which associate with SCC, middle third).
A— Smoking/alcohol are risk factors for SCC (middle third), not adenocarcinoma (distal).
C, D, E— Not major risk factors for esophageal adenocarcinoma.
Q18 · Stress Ulcers · Curling vs. Cushing
A 28-year-old man is admitted to the ICU following a severe thermal burn covering 40% of his body surface area. Within 48 hours, he develops acute gastric erosions with hemorrhage. Which stress ulcer syndrome is this, and what is its mechanism?
ACurling ulcer — stress from burns → gastric vasospasm → ischemic necrosis of mucosa
BCushing ulcer — stress from burns causing increased acid secretion
CH. pylori-induced ulcer from secondary infection
DZollinger-Ellison syndrome from stress-induced gastrinoma
EGERD-induced ulcer from reflux
Correct: A — Curling ulcer from burn-induced ischemia
Curling ulcer occurs in the setting of severe thermal burns. Mechanism: stress → splanchnic vasoconstriction → gastric mucosal ischemia → necrosis and ulceration. Multiple acute erosions/ulcers develop in the stomach and duodenum, often with hemorrhage.
Cushing ulcer (in contrast) occurs with cerebral lesions (head trauma, tumor, hypothalamic damage) and is mediated by vagal stimulation → increased acid secretion → ulceration.
Key distinction:
• Curling = burns → ischemia
• Cushing = cerebral lesion → hypersecretion
B— Cushing (cerebral lesion), not Curling (burn), involves acid hypersecretion.
C, D, E— Not stress ulcers.
Q19 · Gastric Cancer Spread · Metastatic Signs
A 68-year-old woman presents with a palpable, hard supraclavicular lymph node and ascites. Imaging and biopsy reveal metastatic gastric adenocarcinoma. Which eponymous sign represents metastatic gastric cancer to the supraclavicular (left) node?
AVirchow node — right supraclavicular metastasis from left upper quadrant cancer
BVirchow node — left supraclavicular metastasis (sentinel node from stomach/pancreas/biliary cancers)
CSister Mary Joseph node — umbilical nodule from peritoneal metastasis
DKrukenberg tumor — solitary ovarian metastasis from gastric cancer in women
EAll of the above are seen in disseminated gastric cancer
Correct: B — Virchow node (left supraclavicular)
Three key metastatic manifestations of gastric cancer:
Virchow node = enlarged LEFT supraclavicular (sentinel) node from gastric, pancreatic, or biliary cancers; represents metastasis via the thoracic duct
Sister Mary Joseph node = hard nodule at the umbilicus from peritoneal metastasis; represents disseminated intra-abdominal disease
Krukenberg tumor = metastatic gastric cancer (usually signet ring type) to both ovaries in women; often occurs bilaterally
A— Right supraclavicular is not the classic Virchow presentation.
C, D— These ARE seen in gastric cancer, but B is the answer to this question about the supraclavicular node.
Q20 · PUD Hemorrhage · Endoscopic & Medical Management
A 65-year-old man on aspirin for CAD presents with melena and hemodynamic instability. Endoscopy reveals a bleeding duodenal ulcer. After hemostasis is achieved endoscopically (clipping), he is started on high-dose IV omeprazole. Which best explains why PPI therapy reduces rebleeding risk after endoscopic intervention?
APPIs directly clot blood at the ulcer site
BPPIs suppress gastric acid secretion → raise gastric pH → promote clot stability and wound healing
CPPIs eradicate H. pylori infection
DPPIs increase mucosal blood flow to the ulcer
EPPIs are only effective if H. pylori is eradicated first
Correct: B — PPI suppresses acid; raises pH to promote clot stability
After endoscopic hemostasis (mechanical intervention like clipping or cautery), high-dose PPI therapy is critical to prevent rebleeding. PPIs work by suppressing gastric acid secretion via the H⁺/K⁺-ATPase, raising the gastric pH. Higher pH:
• Stabilizes fibrin clots at the ulcer base
• Prevents peptic digestion of forming granulation tissue
• Promotes epithelial wound healing
This combination of endoscopic intervention + acid suppression significantly reduces rebleeding risk.
A— PPIs do not directly clot; endoscopy does.
C— Acid suppression reduces rebleeding independent of H. pylori status.
D, E— Not the primary mechanisms of PPI benefit in acute bleeding.