Two cases of pulmonary paragonimiasis on FDG-PET CT imaging

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1 CASE REPORT Annls of Nucler Medicine Vol. 20, No. 4, , 2006 Two cses of pulmonry prgonimisis on FDG-PET CT imging Ie Ryung YOO, Hyun Jin PARK, Joo HYUN O, Yong An CHUNG, Hyung Sun SOHN, Soo Kyo CHUNG nd Sung Hoon KIM Deprtment of Rdiology, The Ctholic University of Kore, College of Medicine, Kngnm St. Mry s Hospitl, Seoul, Repulic of Kore Positron emission tomogrphy (PET) using 18 F-fluorodeoxyglucose (FDG) is useful in cncer dignosis owing to its sensitivity to the differences in glucose metolic rte etween enign nd mlignnt diseses, especilly in the lung. One pitfll in PET imging of lung disese, however, is the overlp in metolic rte of inflmmtory nd neoplstic entities. Prgonimisis is foodorne prsitic disese tht cuses the pulmonry nd pleurl inflmmtion. We present two cses of pulmonry prgonimisis tht showed high uptke suggestive of tumor on FDG-PET CT imges, oth confirmed on histopthology y visuliztion of Prgonimus westermni eggs in the involved tissues. Key words: prgonimisis, Prgonimus westermni, lung, positron-emission tomogrphy CASE REPORT PET using 18 F-FDG is frequently used to chrcterize pulmonry lesions suspicious for mlignncy. However, incresed 18 F-FDG uptke in enign pulmonry lesions is not uncommon, nd cn e seen in ctive grnulomtous diseses such s tuerculosis, fungl infection, srcoidosis, nd other inflmmtory entities. Prgonimisis is reltively rre cuse of pulmonry disese; there hve een only few reported cses of pulmonry prgonimisis s cuse of flse-positive results on FDG-PET exmintions. We hve found two cses of pulmonry prgonimisis which were flse-positive for mlignncy on FDG-PET CT scn. Cse 1 A 49-yer-old mn ws referred to us from locl clinic in June 2004 for left upper qudrnt dominl pin nd solitry pulmonry nodule (SPN) in the left lung. The ptient hd 30 pck-yer smoking history. Routine Received Octoer 11, 2005, revision ccepted Jnury 6, For reprint contct: Sung Hoon Kim, M.D., Deprtment of Rdiology, Kngnm St. Mry s Hospitl, The Ctholic University of Kore, Seocho-gu, Bnpo-dong, #505, Seoul, , Repulic of Kore. E-mil: sghnk@ctholic.c.kr lortory tests were positive only for mild eosinophili of 8.4% (norml, less thn 5%). Blood nd urine cultures, s well s sputum cultures for cteri nd cid-fst orgnisms, were negtive. Chest X-ry showed ptchy left upper loe opcity ner the ortic rch. Chest CT (Fig. 1) showed 28 mm 26 mm irregulr cvitry nodule in the nterior segment of the left upper loe, nd severl enlrged medistinl nodes djcent to the ortic rch. FDG-PET CT (Biogrph LSO: Siemens Medicl Solutions, Knoxville, Tenn.) demonstrted FDG uptke with SUV of 4.0 in the cvitry lesion, nd slightly incresed uptke in the medistinl lymph nodes (Fig. 2, ). Becuse inflmmtory uptke tends to decrese nd mlignnt uptke tends to increse over time, two-hour delyed imges were susequently otined. The pek SUV of the cvitry lesion t 2 hours ws 4.1, n insignificnt increse of 2.5%. The ptient ws trnsferred to the deprtment of thorcic surgery for open lung iopsy, nd then underwent left upper loe segmentectomy. The pthologic dignosis from oth frozen nd permnent sections ws prgonimisis. Microscopic imges (Fig. 3) showed eggs of Prgonimus westermni (rrowheds) surrounded y chronic inflmmtion nd firosis. Cse 2 A 56-yer-old mn ws referred from locl clinic in April 2004 with one-month history of lood-tinged Cse Report 311

2 Fig. 1 A 49-yer-old mn presenting with left upper qudrnt dominl pin nd SPN of the left lung in June Chest CT depicted n irregulr cvitry nodule in the nterior segment of left upper loe (rrow), nd few enlrged medistinl nodes djcent to the ortic rch (short rrow). Fig. 3 Photomicrogrph (H&E, 40) revels operculted, ovl yellowish colored eggs of Prgonimus westermni (rrowheds), surrounded y chronic inflmmtion nd firosis. Bronchil mucos is eroded. Fig. 2 Axil PET () nd xil PET CT fusion () imges demonstrted modertely incresed FDG uptke in the cvitry lesion of the left upper loe (rrows), nd mild FDG ctivity in enlrged lymph nodes in the prortic nodl sttion (short rrows). 312 Ie Ryung Yoo, Hyun Jin Prk, Joo Hyun O, et l Fig. 4 A 56-yer-old mn presenting with lood tinged sputum during 1 month in April Chest CT (&) demonstrted n irregulr nodule with tiny cvity nd surrounding ground-glss opcity in the left lower loe (rrow), nd enlrged left hilr denopthy (short rrow). Smll mount of fluid collection ws noted. Annls of Nucler Medicine

3 d e Fig. 5 Mximum intensity projection PET (), xil PET (&d) nd xil PET CT (c&e) imges reveled mild to moderte FDG uptke in the lung lesion (rrows) nd enlrged left hilr denopthy (short rrows). c sputum. Routine lortory results, including exmintion for cteri nd cid-fst orgnisms, were nonspecific except for n elevted eosinophil count of 12.3%. Chest X-ry showed ill-defined consolidtion in the left lower loe. A chest CT showed n irregulr cvitry nodule surrounded y ground-glss opcity in the lterl sl segment of the left lower loe, nd smll left pleurl effusion (Fig. 4). Significnt left hilr denopthy ws lso identified (Fig. 4). The initil pthologic results from oth trnsronchil nd trnsthorcic needle iopsies were of chronic inflmmtion without evidence of mlignnt cells. However, FDG-PET CT demonstrted SUVs in the nodule nd the lymphdenopthy of 3.9 nd 4.1, respectively (Fig. 5, e). Becuse mlignncy ws still suspected, repet iopsies were performed, nd prgonimus infection ws eventully dignosed. The ptient egn prziquntel therpy, nd follow-up chest CT performed 2 weeks lter showed mrked diminution in size of the nodule with thinning of the cvity wlls (Fig. 6). Cse Report 313

4 Fig. 6 Two weeks follow-up chest CT depicted mrkedly diminished size of the nodule with thinning of the cvity wlls (rrow). DISCUSSION PET using FDG is highly ccurte in evluting pulmonry lesions, iding in the noninvsive preopertive stging of lung cncer in the pst decde. 1,2 Although nodules less thn 1 cm cnnot e evluted ccurtely, the overll sensitivity nd specificity of FDG-PET for the dignosis of pulmonry lesions re high. 3 FDG-PET imging tkes dvntge of the higher metolic rte of tumor cells to show incresed ccumultion of FDG in mlignnt lesions. However, n incresed metolic rte is lso oserved in inflmmtion. 4 Mny reports hve demonstrted incresed FDG uptke in inflmmtory, infectious nd grnulomtous lung diseses including prsite infesttions, cteril, nd fungl infections, nd tuerculosis In recent met-nlysis y Could et l., 1 the estimted sensitivity of PET for identifying lung mlignncies is 96.8% nd its specificity is 77.8%. It is well known tht most lung mlignncies hve greter uptke of FDG thn norml tissue. Of the vrious cutoff vlues, threshold for single time point SUV of hs een recommended s the optiml threshold for differentiting enign from mlignnt pulmonry lesions, despite considerle overlp of enign nd mlignnt in this rnge Recently, scnners comining functionl nd ntomicl modlities hve een developed. Of these, use of PET CT hs rpidly incresed worldwide. It offers significnt dvntges in loclizing FDG uptke, distinguishing pthologic from physiologic uptke, nd monitoring disese progression. Especilly in non-smll cell lung cncer, PET CT hs proven to e superior over PET lone or CT lone in disese stging. 17 We use PET CT scnning routinely in our hospitl. Zhung et l. 18 reported tht dul-time-point FDG-PET my e useful in distinguishing enign from mlignnt lesions y exploiting the erly pek nd erly wshout FDG from inflmmtory tissues. Kuot et l. 19 showed improved per-ptient sensitivity from 78% with imging t 1 hour to 94% with imging t 2 hours. Mtthies et l. 20 reported tht dul-time-point scnning with threshold vlue of 10% increse from 70 min to 123 min chieved sensitivity of 100% with specificity of 89%. In one of our cses, the uptke incresed y only 2.5% etween the two time points, suggesting enignity. Despite the ove mentioned efforts, the specificity of FDG-PET is still lower in geogrphic regions with high prevlence of grnulomtous disese due to n incresed rte of flse positives. Goo et l. 5 reported tht 9 of 10 tuerculoms demonstrted FDG uptke with men pek SUV of 4.2 ± 2.2. Croft et l. 6 concluded tht the low specificity of their results in differentiting non-smll cell lung cncer from enign SPNs might e relted to high endemic rte of histoplsmosis. Prgonimisis is food-orne prsitic disese common in Southest Asi, especilly in Jpn, Kore, the Philippines, Tiwn, nd prts of Chin. The high endemic rtes of prgonimisis re relted to dietry hits nd methods of food preprtion common to these res. The rdiologic findings of this prsite infesttion when it involves the lung re quite vrile, mking dignosis difficult with imging lone. Dignosis egins with thorough history, nd the operculted eggs of Prgonimus in sputum is the most specific indictor of the disese. Alterntively, if the clinicl history is suspicious ut the sputum negtive for eggs, the dignosis cn e mde with n enzyme-linked immunosorent ssy (ELISA). 7,21,22 Therefore, we suggest tht in the setting of ptient with lung lesion with equivocl imging findings, history of hndling nd/or eting freshwter cr or cryfish in n endemic re, nd eosinophili, prsitic disese needs to e included in the differentil dignosis. In conclusion, positive results on n FDG-PET scn must e interpreted with cution in geogrphic regions with high prevlences of prsites, tuerculosis, nd fungl disese. REFERENCES 1. Could MK, Mclen CC, Kuschner WG, Rydzk CE, Owens DK. Accurcy of positron emission tomogrphy for dignosis of pulmonry nodules nd mss lesions. JAMA 2001; 285: Kelly RK, Trn T, Holmstrom A, Murr J, Segurol RJ Jr. Accurcy nd cost-effectiveness of [ 18 F]-2-fluoro-deoxy- D-glucose positron emission tomogrphy scn in potentilly resectle non-smll cell lung cncer. Chest 2004; 125: Nomori H, Wtne K, Ohtsuk T, Nruke T, Suemsu K, Uno K. Evlution of F-18 fluorodeoxyglucose (FDG) PET scnning for pulmonry nodules less thn 3 cm in dimeter, with specil reference to the CT imges. Lung Cncer 2004; 45: Ie Ryung Yoo, Hyun Jin Prk, Joo Hyun O, et l Annls of Nucler Medicine

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