Gastric anisakiasis presenting as a vanishing tumor.

Gastric anisakiasis might present as a submucosal tumor-like lesion in esophagogastroduodenoscopy. Cautious search is needed when it is suspected in order to avoid misdiagnosis and unnecessary invasive procedures.

A 46‐year‐old man presented with 1 day history of epigastric pain and soft stool after having sushi including mackerel (Scomber japonicus). Physical examination showed epigastric tenderness without rebound tenderness or guarding. Laboratory studies were within normal limit except for an elevated leukocyte count at 10 800/μL (0.5% eosinophil) and a C‐reactive protein level at 3.05 mg/dL. We suspected gastric anisakiasis and thus performed esophagogastroduodenoscopy (EGD), which disclosed a submucosal tumor‐like lesion approximately 6 cm in diameter with geographic ulcer on its surface in the greater curvature of the gastric fundus (Figure 1A). Cautious search revealed an Anisakis larva penetrating into the edematous mucosa posterior to the tumor‐like lesion (Figure 1B, arrow). After removal of the larva with biopsy forceps, the submucosal tumor‐like lesion flattened out immediately, better visualizing the ulcer (Figure 1C). The patient was subsequently treated with oral proton pump inhibitor. Repeat EGD 4 months later showed only an ulcer scar while the patient was asymptomatic (Figure 2).

Figure 1

Esophagogastroduodenoscopy disclosed a submucosal tumor‐like lesion in the greater curvature of the gastric fundus (A). An Anisakis larva was found penetrating into the mucosa posterior to the tumor‐like lesion (B). The submucosal tumor‐like lesion flattened out after removal of the larva, better revealing the ulcer (C)

Figure 2

Repeat esophagogastroduodenoscopy 4 mo later demonstrated an ulcer scar

Anisakiasis is a disease related to infection of Anisakis larvae through consumption of raw seafood. It is particularly popular in Japan but has also been reported in a number of countries. Gastric anisakiasis is caused by gastric mucosal penetration of larvae and can present with a variety of manifestations and endoscopic findings. While epigastric pain is the most frequent complaint, other symptoms including nausea, vomiting, diarrhea, and allergic signs have also been reported.1, 2 EGD could be both diagnostic and therapeutic in gastric anisakiasis patients, by visualizing and removing the larvae. However, penetrating Anisakis larvae are not always immediately seen, as in the present case. Frequent EGD findings include mucosal edema, ulcers, as well as submucosal tumor formation.1, 3

Relevant history such as epigastric pain after recent consumption of raw seafood should warrant watchful investigation for Anisakis larvae as well as supporting findings such as surrounding mucosal edema, in order to avoid misdiagnosis and unnecessary invasive procedures. In cases where Anisakis larvae are not appreciated, serologic tests could be considered. Elevated total and Anisakis‐specific serum IgE levels help diagnose acute anisakiasis but with a low specificity, while Anisakis‐specific serum IgA and IgG levels (especially tested in paired sera) contribute to detection of Anisakis infection with a higher specificity.4, 5 Meanwhile, a physician should always keep a wide differential diagnosis list for gastric submucosal tumor (non‐neoplastic: cysts, ectopic pancreatic tissue, and inflammation such as parasitic infestation by Anisakis; neoplastic: gastrointestinal stromal tumor, lymphoma, carcinoid, leiomyoma, schwannoma, neurofibroma, lipoma, and lymphangioma) in mind.6, 7

CONFLICT OF INTEREST

The authors have stated explicitly that there are no conflicts of interest in connection with this article.