A 59-year-old Japanese man was referred to our hospital in March 1998 due to an acute
onset of upper abdominal pain, which had occurred a few hours after ingesting raw
mackerel. The physical examination showed epigastric tenderness. Upper endoscopy identified
a reddish tumor, 65 mm in its largest diameter, in the gastric fundus (Figure [1]). The tumor had a smooth surface, with irregular and shallow ulcers covered by blood
coagula. The patient’s abdominal pain subsided immediately, without any treatment.
An upper endoscopic examination carried out two weeks later revealed that the tumor
had regressed (Figure [2]). At this time, the patient’s serum IgGI-A antibody titer to Anisakis larvae increased to 2.09 (normal: < 1.50). On the basis of these findings, a diagnosis
of gastric anisakiasis was established. The patient has been free of any gastrointestinal
symptoms during a subsequent follow-up period of 26 months.
Gastric anisakiasis is a condition characterized by infestation of Anisakis larvae in the gastric mucosa after the ingestion of raw or undercooked fish. The
clinical, radiological, and endoscopic features of the disease have been well documented
[1]. Yamasaki et al. [2] were the first to report a gastric protrusion of obscure origin that rapidly regressed,
and described these lesions as “vanishing tumor.” It is presumed that the lesion is
caused by penetration of the Anisakis larvae into the gastric wall [3]
[4]
. The common endoscopic feature of the tumors is a smooth protrusion. As in the case
described here, vanishing tumors caused by anisakiasis have also previously been observed
in the gastric fundus [3]
[4]
.
Vanishing tumor is easily diagnosed by endoscopy. However, Anisakis larvae have rarely been confirmed by the procedure [5]. In the present case, increased antibody to Anisakis larvae was the key to the diagnosis. Vanishing tumors should not be misdiagnosed
as neoplastic lesions, and serological testing for Anisakis larvae should be considered when there are similar findings.
Figure 1Upper endoscopy reveals a reddish tumor in the gastric fundus. The tumor has a smooth
surface and shallow ulcers
Figure 2Upper endoscopy two weeks later shows that the tumor has regressed
