Two cases of pulmonary paragonimiasis on FDG-PET CT imaging

Colonic Parasitic Infection Mimicking Peritoneal Seeding on 18F-FDG PET/CT

A 77-year-old man with anorexia and weight loss for 6 months received a diagnosis of gastric cancer by endoscopy and referred for F-FDG PET/CT for initial staging. F-FDG PET/CT showed multiple foci of increased FDG uptake with diffuse wall thickening and multiple diverticula. The differential diagnoses were peritoneal seeding and multiple diverticulitis. The patient underwent curative total gastrectomy, and the lesion was diagnosed as poorly differentiated adenocarcinoma by histological examination. He underwent anterior resection of the sigmoid colon for exploration. The nodular lesions of the sigmoid colon were diagnosed by histopathologic examination as chronic diverticulitis caused by a parasitic infection.

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.

CASE PRESENTATION

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.

CONCLUSION

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.

Breast Sparganosis Incidentally Detected by FDG PET/CT

Sparganosis is a rare, parasitic infection that is caused by the plercercoid tapeworm larvae of the genus Spirometra. Sparganosis is transmitted by ingestion of larvae-containing water or intermediate hosts, such as raw amphibians, and usually presented with a subcutaneous nodule in the abdominal wall, extremities, and genital organs. Among the various involved organs, the breast is a seldom encountered site for sparganosis. However, breast sparganosis has clinical importance, since it is generally presented with an indolent palpable mass that mimics malignancy, even without evidence of inflammation. Herein, we report a case of breast sparganosis that was detected incidentally by FDG PET/CT during staging work ups in a patient with gall bladder cancer.

Chest CT features of North American paragonimiasis

OBJECTIVE

The purpose of this study was to characterize the chest CT findings of North American paragonimiasis due to Paragonimus kellicotti in the largest (to our knowledge) case series reported to date and to compare the findings with those reported for paragonimiasis infections in other regions.

MATERIALS AND METHODS

A retrospective review was performed of chest CT examinations of eight patients with North American paragonimiasis treated at our institution between 2006 and 2010. Findings were characterized by site of involvement, including lungs and pleura, heart and pericardium, lymph nodes, and upper abdomen.

RESULTS

The most common chest CT findings in this case series were pleural effusions and internal mammary and cardiophrenic lymphadenopathy. Pulmonary parenchymal findings included peripheral lung nodules of 1-3.5 cm in size with surrounding ground-glass opacity; many nodules had a linear track to the pleural surface that may correspond to the worm's burrow tunnel. Pericardial involvement (5/8 patients) and omental inflammation (5/7 patients), which are uncommon in Asian paragonimiasis, were common in this series.

CONCLUSION

Pleural and pulmonary features of North American paragonimiasis are generally similar to those reported from Asia. The presence of a track between a pulmonary nodule and the pleura may help distinguish paragonimiasis from mimickers, including chronic eosinophilic pneumonia, tuberculosis, fungal infection, or malignancy. Pericarditis, lymphadenopathy, and omental inflammation were more common in our series than in reports on paragonimiasis from other regions. These differences may be related to the infecting parasite species or to the fact that radiologic examinations in the present series were performed relatively early in the course of infection.

A pulmonary paragonimiasis case mimicking metastatic pulmonary tumor

Pulmonary paragonimiasis is a relatively rare cause of lung disease revealing a wide variety of radiologic findings, such as air-space consolidation, nodules, and cysts. We describe here a case of pulmonary paragonimiasis in a 27-year-old woman who presented with a 2-month history of cough and sputum. Based on chest computed tomography (CT) scans and fluorodeoxyglucose positron emission tomography (FDG-PET) findings, the patient was suspected to have a metastatic lung tumor. However, she was diagnosed as having Paragonimus westermani infection by an immunoserological examination using ELISA. Follow-up chest X-ray and CT scans after chemotherapy with praziquantel showed an obvious improvement. There have been several reported cases of pulmonary paragonimiasis mimicking lung tumors on FDG-PET. However, all of them were suspected as primary lung tumors. To our knowledge, this patient represents the first case of paragonimiasis mimicking metastatic lung disease on FDG-PET CT imaging.

Radiation dosimetry and biodistribution of (99m)Tc-ethylene dicysteine-deoxyglucose in patients with non-small-cell lung cancer

Purpose

To assess the radiation dosimetry and biodistribution of ^99mTc-labeled ethylene dicysteine deoxyglucose (^99mTc-EC-DG) in patients with non-small-cell lung cancer (NSCLC).

Methods

Serial whole-body scans were acquired 0, 2, 4, 6 and 24 h after injection of ^99mTc-EC-DG (925 MBq) in seven NSCLC patients. Radiation dosimetry, blood clearance and SPECT imaging of the primary tumor were assessed.

Results

The critical organ was the bladder wall, with average radiation absorbed dose over all seven patients of 2.47×10⁻² mGy/MBq. The average effective dose equivalent and effective dose were 6.20×10⁻³ mSv/MBq (6.89 mSv/1,110 MBq) and 5.90×10⁻³ mSv/MBq (6.54 mSv/1,110 MBq), respectively. The primary tumor was visualized with SPECT in six patients. On final pathology, one patient had a granuloma, which did not enhance with ^99mTc-EC-DG.

Conclusion

^99mTc-EC-DG has acceptable dosimetric and biodistribution properties as a diagnostic tumor-imaging agent. Future studies are planned to evaluate its diagnostic potential.