Anisakiasis mimics cancer recurrence: two cases of extragastrointestinal anisakiasis suspected to be recurrence of gynecological cancer on PET-CT and molecular biological investigation.
BACKGROUND
We report two cases of anisakiasis lesions that were initially suspected to be recurrence of gynecological cancer by positron emission tomography-computed tomography (PET-CT). Both cases were extragastrointestinal anisakiasis that is very rare.


METHODS
The first case was a patient with endometrial cancer. At 19 months after surgery, a new low density area of 2 cm in diameter in liver segment 4 was found on follow-up CT. In PET-CT, the lesion had abnormal (18)fluoro-deoxyglucose (FDG) uptake with elevation in the delayed phase, with no other site showing FDG uptake. Partial liver resection was performed. A pathological examination revealed no evidence of malignancy, but showed necrotic granuloma with severe eosinophil infiltration and an irregular material with a lumen structure in the center. Parasitosis was suspected and consultation with the National Institute of Infectious Diseases (NIID) showed the larvae to be Anisakis simplex sensu stricto by genetic examination. The second case was a patient with low-grade endometrial stromal sarcoma (LG-ESS). At 8 months after surgery, swelling of the mediastinal lymph nodes was detected on CT and peripheral T-cell lymphoma was diagnosed by biopsy. A new peritoneal lesion with abnormal FDG uptake was detected on pre-treatment PET-CT and this lesion was increased in size on post-treatment PET-CT. Tumorectomy was performed based on suspected dissemination of LG-ESS recurrence. The findings in a pathological examination were similar to the first case and we again consulted the NIID. The larvae was identified as Anisakis pegreffi, which is a rare pathogen in humans. Having experienced these rare cases, we investigated the mechanisms of FDG uptake in parasitosis lesions by immunohistochemical staining using antibodies to glucose transporter type 1 (GLUT-1) and hexokinase type 2 (HK-2). While infiltrated eosinophils were negative, macrophages demonstrated positive for both antibodies. Therefore, mechanisms behind FDG uptake may involve macrophages, which is common among various granulomas. This is the first report to investigate parasitosis in such a way.


CONCLUSIONS
These cases suggest that anisakiasis is a potential differential diagnosis for a lesion with FDG uptake in PET-CT, and that it is difficult to distinguish this disease from a recurrent tumor using PET-CT alone.
Department of Obstetrics and Gynecology, Keio University School of Medicine, Shinanomachi 35 Shinjuku-ku, Tokyo, 160-8582, Japan.
Yuya
Y
Nogami
Department of Pathology, Keio University School of Medicine, Shinanomachi 35 Shinjuku-ku, Tokyo, 160-8582, Japan.
Yoko
Y
Fujii-Nishimura
Department of Obstetrics and Gynecology, Keio University School of Medicine, Shinanomachi 35 Shinjuku-ku, Tokyo, 160-8582, Japan. kbanno@z7.keio.jp.
Kouji
K
Banno
Department of Obstetrics and Gynecology, Keio University School of Medicine, Shinanomachi 35 Shinjuku-ku, Tokyo, 160-8582, Japan.
Atsushi
A
Suzuki
Department of Obstetrics and Gynecology, Keio University School of Medicine, Shinanomachi 35 Shinjuku-ku, Tokyo, 160-8582, Japan.
Nobuyuki
N
Susumu
Department of Surgery, Keio University School of Medicine, Shinanomachi 35 Shinjuku-ku, Tokyo, 160-8582, Japan.
Taizo
T
Hibi
Department of Radiology, Keio University School of Medicine, Shinanomachi 35 Shinjuku-ku, Tokyo, 160-8582, Japan.
Koji
K
Murakami
Division of Diagnostic Pathology, Keio University School of Medicine, Shinanomachi 35 Shinjuku-ku, Tokyo, 160-8582, Japan.|Department of Pathology, Saitama Medical University, Moroyama-machi 38, Iruma-gun, Saitama, 350-0495, Japan.
Taketo
T
Yamada
Department of Parasitology, National Institute of Infectious Diseases, Toyama 1-23-1 Shinjuku-ku, Tokyo, 162-8640, Japan.
Hiromu
H
Sugiyama
Department of Parasitology, National Institute of Infectious Diseases, Toyama 1-23-1 Shinjuku-ku, Tokyo, 162-8640, Japan.
Yasuyuki
Y
Morishima
Department of Obstetrics and Gynecology, Keio University School of Medicine, Shinanomachi 35 Shinjuku-ku, Tokyo, 160-8582, Japan.
Daisuke
D
Aoki
D000328:Adult; D017129:Anisakiasis / Q000175:diagnosis*; D003937:Diagnosis, Differential; D016889:Endometrial Neoplasms / Q000473:pathology / Q000628:therapy; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000469:parasitology*; D008198:Lymph Nodes / Q000469:parasitology*; D008875:Middle Aged; D064847:Multimodal Imaging; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000378:metabolism; D018203:Sarcoma, Endometrial Stromal / Q000473:pathology / Q000628:therapy; D014057:Tomography, X-Ray Computed / Q000379:methods*
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
Anisakis; Extragastrointestinal anisakiasis; Genetic examination; Glucose transporter type 1; Gynecological cancer; Hexokinase type 2; PCR; PET-CT