papillary thyroid carcinoma being the most common type of differentiated thyroid malignancy has a predilection for spread through the lymphatic system and thus commonly involves the central and lateral compartmental lymph nodes of the cervical region .
soft tissue metastasis is even rarer and amenable to radioiodine treatment similar to metastatic lesions in the lung and bones when they concentrate iodine .
the concerned case is unique in the sense that the involvement simultaneously of three soft tissue organs is present with different iodine - concentrating abilities , whereas a review of the literature did not find the simultaneous presence of iodine - concentrating metastasis in one organ , iodine - nonconcentrating metastasis in another organ , and multiorgan soft tissue metastasis in the same patient .
the case report also emphasizes possible hematogenous route of metastasis which is rare in papillary thyroid malignancy .
a 42-year - old male patient with a history of total thyroidectomy and bilateral cervical nodal dissection positive for papillary carcinoma thyroid was referred to our department for a follow positron emission tomography - computed tomography ( pet - ct ) scan for evaluation of lung nodules and muscle lesions that he developed five years after primary treatment . during the follow - up , prompted by elevated thyroglobulin levels , an iodine-131 whole body scan and single photon emission tomography - computed tomography ( spect - ct ) [ figure 1 ] showed positive lesions , one in the liver and another in the left gluteal region .
a fludeoxyglucose ( fdg ) pet - ct scan [ figure 2 ] was done to find more lesions and revealed metabolically active lesions in liver segment vi [ figure 3 ] and the left gluteus and a new paraspinal muscle lesion at the nape of the neck [ figure 4 ] , whereas the lung nodules were metabolically inactive [ figure 5 ] .
a post - therapy scan [ figure 6 ] at a therapeutic dose of 200 mci of iodine-131 revealed iodine concentration in the liver and a gluteal lesion , whereas there was no concentration in lung nodules and neck lesion .
the present fdg pet ct scan [ figure 7 ] as a response evaluation six month post treatment revealed a metabolic response in the liver and gluteal lesion [ figure 8 ] , but an increasing size of the neck lesion [ figure 9 ] and lung nodules [ figure 10 ] .
presently , the patient is put on redifferentiation therapy with sorafenib and suppressive doses of thyroxin .
the single photon emission tomography - computed tomography ( spect  ct ) scan shows iodine - concentrating lesion in left gluteal muscle left gluteal lesions were metabolically active in pretherapy positron emission tomography - computed tomography ( pet  ct ) study the new lesion at nape of neck fludeoxyglucose ( fdg ) activity but not lung nodules the 200 mci post - therapy scan concentration in liver and gluteal lesion but no concentration in neck lesion and lung nodules .
the positron emission tomography - computed tomography ( pet  ct ) scan after six months iodine therapy shows treatment response in liver soft tissue deposit in the neck demonstrating increase in size and fdg uptake ( disease progression )
papillary thyroid carcinoma is the most common type of differentiated thyroid carcinoma accounting for at least 70% of all follicular cell - derived thyroid malignancies and is considered to be a relatively indolent tumor in which distant metastasis and death are rare .
the five - year survival rate for papillary thyroid cancer according to the stage is 100% for stage i and ii , 93% for stage iii , and 51% for stage
distant metastasis is the principal cause of death in cases of well - differentiated thyroid carcinomas .
about 10% of papillary carcinomas develop distant metastasis , with about 50% of patients having such metastasis at the time of diagnosis .
the prognosis of these patients is poor , and over 50% of the patients are likely to die within five years , irrespective of the histology of the tumor .
distant metastasis , although relatively uncommon , has been known to occur most commonly in the lungs , followed in frequency by bone and brain ( 0.1 to 5.0% ) .
isolated cases of soft tissue metastasis have been documented in the orbit , skull , skin , muscles , liver , spleen , pancreas , and adrenal gland.[613 ] metastatic lesions have also been documented in silent or occult thyroid neoplasms .
radioactive iodine treatment is considered to be the first line of treatment for distant metastasis from thyroid carcinomas that concentrate a significant amount of radioiodine . unlike our patient who developed metastatic disease and related symptoms
five years after treatment of primary disease , for patients who develop distant metastatic disease at the time of initial diagnosis , a positive iodine-131 whole body scan post treatment of primary lesions in the neck makes way for successful radioiodine treatment of metastasis . however , solitary metastatic lesions which do not concentrate radioiodine can be dealt with surgical removal and/or external beam radiation . to add to the confusion , our patient showed radioiodine concentration in one of the muscle lesions and liver but no concentration in another muscle lesion and lung nodules .
consequently , the muscle lesions responded to radioiodine treatment , whereas the neck lesion and lung nodules showed progression over the period of treatment .
the patient has been put on a suppressive dose of thyroxin and redifferentiation therapy . in the past ,
retinoic acid , thalidomide , and rosiglitazone showed efficacy in redifferentiation therapy of iodine - nonconcentrating thyroid malignancy metastatic lesions ; however , currently , sorafenib ( 400 mg twice daily ) and sunitinib ( 50 mg daily for 28 days followed by 14 days of no treatment per cycle ) , approved for other indications , show promise for thyroid cancer .
 distant soft tissue metastasis and the simultaneous presence of iodine concentrating and nonconcentrating lesions in papillary thyroid cancer are extremely rare . the concerned patient , a histopathologically proven case of papillary thyroid cancer with nodal metastases treated with total thyroidectomy , bilateral cervical nodal dissection , and radioablation , subsequently developed lung , muscle , and liver metastasis . 
 triggered by increased thyroglobulin , the iodine-131 whole body scan and 200 mci iodine-131 post - therapy scan showed a left gluteus maximus lesion and a liver lesion . 
 fludeoxyglucose ( fdg ) positron emission tomography - computed tomography ( pet - ct ) scan intended to find additional lesions revealed iodine and fdg nonconcentrating bilateral pulmonary nodules and a single fdg avid hepatic and two muscle metastases . 
 although fdg concentration in metastatic pulmonary nodules is generally low , the ct characteristics were classical for metastatic lesion . a follow - up fdg pet - ct study six months after 200 mci iodine-131 radioablation showed treatment response in muscle and liver lesions but not lungs . 
INTRODUCTION
CASE REPORT
DISCUSSION