|Year : 2012 | Volume
| Issue : 1 | Page : 126-128
Lymphadenopathy resulting from acute toxoplasmosis mimicking relapse of non-Hodgkin's lymphoma on fluorodeoxyglucose positron emission tomography/computed tomography
Prathamesh Joshi1, Vikram Lele1, Pravin Mahajan2
1 Department of Nuclear Medicine and PET-CT, Jaslok Hospital and Research Centre, Worli, India
2 Department of Histopathology, Raheja Hospital (A Fortis associate), Mahim, Mumbai, India
|Date of Web Publication||19-Apr-2012|
Department of Nuclear Medicine and PET-CT, Jaslok Hospital and Research Centre, Worli, Mumbai
Source of Support: None, Conflict of Interest: None
We report a case documenting fluorodeoxyglucose (FDG) accumulation in cervical, supraclavicular and axillary lymph nodes resulting from acute toxoplasmosis. A 50-year-old Indian female with history of non-Hodgkin's lymphoma (NHL) of left breast, postchemotherapy status, was found to have hypermetabolic right cervical, supraclavicular and axillary lymph nodes on a surveillance FDG positron emission tomography/computed tomography (PET/CT) scan. Her previous two PET/CT scans were unremarkable with no evidence of metabolically active disease. Therefore, a differential diagnosis of relapse of NHL versus infectious/inflammatory pathology was raised in the report. Biopsy of axillary lymph node demonstrated features characteristic of toxoplasmosis. The serological test results were also compatible with acute toxoplasmosis infection. Infective and inflammatory diseases are known to accumulate FDG, resulting in false positives for malignancy. This case demonstrates lymph nodal toxoplasmosis as a potential cause of false positive FDG PET/CT findings in patients with known malignancy and highlights the importance of histopathological and laboratory correlation for the accurate interpretation of FDG PET/CT scans.
Keywords: FDG PET/CT, infection, lymph nodes, NHL, relapse, toxoplasmosis
|How to cite this article:|
Joshi P, Lele V, Mahajan P. Lymphadenopathy resulting from acute toxoplasmosis mimicking relapse of non-Hodgkin's lymphoma on fluorodeoxyglucose positron emission tomography/computed tomography. J Can Res Ther 2012;8:126-8
|How to cite this URL:|
Joshi P, Lele V, Mahajan P. Lymphadenopathy resulting from acute toxoplasmosis mimicking relapse of non-Hodgkin's lymphoma on fluorodeoxyglucose positron emission tomography/computed tomography. J Can Res Ther [serial online] 2012 [cited 2018 Aug 17];8:126-8. Available from: http://www.cancerjournal.net/text.asp?2012/8/1/126/95192
| > Introduction|| |
F-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) is a valuable non-invasive technique for staging, assessing response to treatment and detecting recurrent disease in various malignancies. However infectious and inflammatory pathologies also accumulate FDG and hence are responsible for false positive scans for malignancy. We present a case of acute toxoplasmosis infection of lymph nodes mimicking relapse of non-Hodgkin's lymphoma (NHL).
| > Case Report|| |
A 50-year-old Indian female with history of NHL of left breast presented for a surveillance F-18 FDG PET/CT scan in 2011. In 2007, she presented with lump in left breast, which on FNAC was suspicious of carcinoma. Patient underwent modified radical mastectomy (MRM) and final histopathology, immunohistochemistry result revealed NHL. Six cycles of chemotherapy were given and the post-therapy F-18 FDG PET-CT scan in 2008 and surveillance scans in 2010 showed no evidence of metabolically active disease. After a period of complete remission of almost three years, during her routine follow up visit, she was found to have right cervical, supraclavicular and axillary lymphadenopathy. F-18 FDG PET/CT was advised to characterize the lymphadenopathy.
F-18 FDG PET/CT demonstrated hypermetabolism in multiple right cervical, supraclavicular and axillary lymph nodes [Figure 1] which were new compared with her previous two negative PET/CT studies. A differential diagnosis of relapse of lymphoma versus infective/inflammatory pathology was given in our report.
|Figure 1: A 50-year-old woman with history of non-Hodgkin's lymphoma of left breast presented for a follow-up FDG PET/CT scan. Maximum intensity projection (MIP) image (A) demonstrating multiple hypermetabolic foci in right cervical region (red arrow) and right axillary region (black arrow) mimicking relapse. (B) Hypermetabolic right cervical (arrow). (C) Axillary lymph nodes (arrow). All the lesions were new compared with her previous two negative FDG PET/CT studies|
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Biopsy of the right axillary lymph node showing maximum metabolic activity (maximum standardized uptake value- 6.5 g/ml) was performed. The histopathology [Figure 2] was characteristic of toxoplasmosis. To confirm, acute infection serological test was ordered. Enzyme-linked fluorescent assay showed 'immunoglobulin M index' of 1.64 (> 0.65 positive) and immunoglobulin G level of > 300 IU/ml (> 8 IU/ml positive);consistent with acute toxoplasmosis infection. For the patient who presents with lymphadenopathy only, a positive IgM titer is an indication of acute infection and an indication for therapy, so she has been started on anti-toxoplasmosis therapy.
|Figure 2: Biopsy of the hypermetabolic right axillary lymph node revealed features characteristic of toxoplasmosis. Photomicrograph of the lymph node reveals (H&E stain, 10×) follicular hyperplasia (arrows in a) and small epithelioid granulomas (arrowheads in b), commonly seen in toxoplasmosis. To confi rm acute toxoplasmosis, serological tests were advised, which were compatible with acute toxoplasmosis infection|
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| > Discussion|| |
Wider utilization of FDG PET in oncologic clinical practice has increasingly led to the realization that inflammatory and infectious processes accumulate FDG, occasionally resulting in false-positives for malignancy. ,, FDG uptake is considered to be due to increased expression of glucose transporters in activated inflammatory cells. In addition, in inflammatory conditions, the affinity of glucose transporters for deoxyglucose is apparently increased by various cytokines and growth factors, a phenomenon that has not been observed in tumors. ,,, This may be the first case documenting FDG accumulation in multiple lymph nodes due to acute toxoplasmosis infection.
Toxoplasmosis is a zoonotic infection in humans caused by the protozoal intracellular parasite Toxoplasma gondii.Toxoplasmic lymphadenitis or glandular toxoplasmosis is the most frequently observed clinical form of acquired toxoplasmosis. Accurate diagnoses of this form of toxoplasmasis is especially important in two groups- pregnant women, who may transmit the infection to their offspring and in patients in whom the clinical picture and lymph node enlargement are suggestive of Hodgkin's disease or other lymphomas. T. gondii is a recognized infection which can be fatal in patients with lymphomas and leukemia. 
Most of the published data on use of FDG PET in toxoplasmosis is in the setting of central nervous system (CNS) complications of acquired immune deficiency syndrome (AIDS). Both toxoplasmosis and lymphoma are frequent CNS complications of AIDS, and it is not always possible to distinguish between the two at CT and magnetic resonance (MR) imaging. FDG PET is considered very useful in this setting.  CNS lymphoma is highly metabolically active, whereas toxoplasmosis is not. Quantitative assessment has shown that the standardized uptake values (SUV) of toxoplasmosis are significantly lower than those of lymphoma, with virtually no overlap between the uptake values of the two conditions. , Considering these findings, we find it important to report that in our case neither the SUV nor visual interpretation of involved lymph nodes was a useful marker to differentiate the lesions as infective (toxoplasmosis) or malignant (lymphoma), illustrating different metabolic behavior from that of toxoplasmosis of CNS.
In conclusion, we present a case of hypermetabolic lymphadenopathy secondary to toxoplasmosis infection mimicking relapse of lymphoma. This case highlights the importance of histopathological and laboratory correlation for the accurate interpretation of FDG PET, PET/CT scans.
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