langerhans cell histiocytosis ( lch ) is a rare neoplastic disease of antigen - presenting cells , with an incidence rate of 4.05.4/1 million individuals .
the most frequent sites of occurrence are skin , bone , central nervous system ( cns ) .
computed tomography ( ct ) , magnetic resonance imaging ( mri ) , ultrasonic scan ( uss ) are mainly for the individual part , while multiple systems involvement need the whole body imaging .
we present an unusual case of lch of the primary thyroid gland , which was confirmed by fine needle aspiration cytology .
in addition to the thyroid gland , 18f - fluorodeoxyglucose ( 18f - fdg ) positron emission tomography ( pet)/ct discovered multiple organs involvement such as pituitary stalk , maxillofacial skin lesion , lungs , and skull .
a 35-year - old man complained with painless progressive asymmetric enlargement of the bilateral thyroid lobes for a year . in the recent 3-month
no hereditary syndromes , family history of cancer , and personal history were disclosed . there was no additional past medical or surgical history .
blood tests revealed a normal full blood count , electrolytes , urea , creatinine , calcium , and phosphate levels .
thyroid function tests reported a thyroid stimulating hormone level of 0.97 ( normal range 0.34.6 uiu / ml ) , free t4 of 21.78 ( normal range 6.624.8
pmol / l ) , thyroglobulin antibodies of 53.20 ( normal range < 30 u / ml ) , thyroid peroxidase antibody of 64.00 ( normal range 0.1610 iu / ml ) .
in addition , serum calcitonin was recorded at < 1.0 ( normal range < 11.8 ng / l ) and urine catecholamine levels were within normal range .
water pressure test revealed explicitly for central diabetes insipidus , and desmopressin acetate was given for 1-month .
uss of the neck , conducted at the referring hospital , reported an enlarged ( 3.1 cm and 2.8 cm in diameter ) bilateral thyroid lobes [ figure 1 ] .
subsequently , a needle biopsy from the thyroid mass revealed features of langerhans cell with the tumor cells staining positive for cd1a , s-100 , negative for cytokeratin [ figure 2 ] .
18fdg pet / ct was performed for further evaluation of lch in the whole body [ figure 4 ] .
the maximum projection image of the pet revealed increased uptake in thyroid gland ( standardized uptake value [ suvmax ] = 9.4 ) [ figure 4a ] , pituitary stalk ( suvmax = 4.9 ) [ figure 4b ] , and maxillofacial skin lesion ( suvmax = 4.9 ) [ figure 4c ] , which corresponded well to bilateral thyroid nodule , the thicking of pituitary stalk , and skin lesion on the ct .
however , ct showed the left lung nodule [ figure 4d ] and the skull destruction [ figure 4e ] without 18fdg uptake .
( a ) an ultrasonic scan ( uss ) of the neck , conducted at the referring hospital , reported multiple keyed acoustic area , basic clear boundary in both thyroid lobes [ b : 3.1 , and a : 2.8 cm in diameter ] .
( b ) an uss of the neck , conducted at the referring hospital , reported multiple keyed acoustic area , basic clear boundary in both thyroid lobes [ b : 3.1 and a : 2.8 cm in diameter ] ( a ) h and e staining [ a : h and e 100 ; b : h and e 400 ] and immunostaining ( cd1a , langerin and s-100 ) of lesions from the thyroid gland lesions .
the lesions from the thyroid gland exhibited positive expression patterns for cd1a [ c : 100 ] , langerin [ d : 100 ] and s-100 [ e : 100 ] , and negative for cytokeratin ( ck ) [ f : 100 ] .
( b ) h and e staining [ a : h and e 100 ; b : h and e 400 ] and immunostaining ( cd1a , langerin and s-100 ) of lesions from the thyroid gland lesions .
the lesions from the thyroid gland exhibited positive expression patterns for cd1a [ c : 100 ] , langerin [ d : 100 ] and s-100 [ e : 100 ] , and negative for ck [ f : 100 ] .
( c ) h and e staining [ a : h and e 100 ; b : h and e 400 ] and immunostaining ( cd1a , langerin and s-100 ) of lesions from the thyroid gland lesions .
the lesions from the thyroid gland exhibited positive expression patterns for cd1a [ c : 100 ] , langerin [ d : 100 ] and s-100 [ e : 100 ] , and negative for ck [ f : 100 ] .
( d ) h and e staining [ a : h and e 100 ; b : h and e 400 ] and immunostaining ( cd1a , langerin and s-100 ) of lesions from the thyroid gland lesions .
the lesions from the thyroid gland exhibited positive expression patterns for cd1a [ c : 100 ] , langerin [ d : 100 ] and s-100 [ e : 100 ] , and negative for ck [ f : 100 ] .
( e ) h and e staining [ a : h and e , 100 ; b : h and e , 400 ] and immunostaining ( cd1a , langerin and s-100 ) of lesions from the thyroid gland lesions .
the lesions from the thyroid gland exhibited positive expression patterns for cd1a [ c : 100 ] , langerin [ d : 100 ] and s-100 [ e : 100 ] , and negative for ck [ f : 100 ] .
( f ) : h and e staining [ a : h and e  100 ; b : h and e  400 ] and immunostaining ( cd1a , langerin and s-100 ) of lesions from the thyroid gland lesions .
the lesions from the thyroid gland exhibited positive expression patterns for cd1a [ c : 100 ] , langerin [ d : 100 ] and s-100 [ e : 100 ] , and negative for ck [ f : 100 ] ( a ) magnetic resonance imaging ( mri ) sections of the head revealing pituitary stalk enlargement .
( b ) mri sections of head revealing pituitary stalk enlargement ( a ) 18f - fluorodeoxyglucose positron emission tomography / computed tomography ( 18fdg pet / ct ) revealed increased uptake in the thyroid gland and maxillofacial skin , in addition to the left lung and skull .
( b ) 18fdg pet / ct revealed increased uptake in the thyroid gland and maxillofacial skin , in addition to the left lung and skull .
( c ) 18fdg pet / ct revealed increased uptake in the thyroid gland and maxillofacial skin , in addition to the left lung and skull .
( d ) 18fdg pet / ct revealed increased uptake in the thyroid gland and maxillofacial skin , in addition to the left lung and skull .
( e ) 18fdg pet / ct revealed increased uptake in the thyroid gland and maxillofacial skin , in addition to the left lung and skull
langerhans cell histiocytosis is a type of histiocytic disorders , which was first reported in 1893 .
the age of onset of lch from infant to adult and it frequently occur in childhood
. final diagnosis of lch is made by histopathology and immunohistochemistry , and there are no specificities only depending on the clinical features or radiologic findings of lch
. the radiologic imaging may provide some characteristics , such as  punched - out  lesion or beveled edge in skull , symmetric flattening of vertebral body , lytic lesion with sclerotic rim and surrounding areas of sclerosis more common in iliac bone , diaphyseal or metaphyseal of long bones involved in children .
otherwise , approximately 70% of patients will also show thickening of the pituitary stalk on mr images .
the mechanism of fdg uptake by malignant tissue or metastatic lesions is due to the enhanced rate of glucose utilization by neoplastic cells .
lch as a type of histiocytic disorders , most of the lesions display a high level of fdg uptake .
the lesions of lch can range from a single system involvement to a multisystem disease .
it may present as a neoplasm , skin rash , lytic bone lesion , emphysematous bullae , interstitial lung disease or present with multiple affected organ systems within the human body .
the most common clinical cns manifestation of lch is diabetes . in this case , the patient underwent a whole - body pet / ct , which was positive for suspicious lesions , pet revealed increased fdg uptake not only in thyroid nodule , but also in the pituitary stalk and maxillofacial skin . in the region of these areas , the intense fdg activity on pet corresponded well to ct and the fusion images .
we also found that the left lung nodule has slighter metabolic ( suvmax 0.5 ) and the skull destruction even nonmetabolic in pet .
it has been reported that pet may showed false - negative in some small bone lesions , such as skull and cerebrum involvement .
hence , it was suggested that combined multiple analysis methods would improve sensitivity and specificity of the whole body lch .
positron emission tomography / computed tomography is a useful tool to rule out the presence of other organ infiltration . as the intent by our case
, it also provides a reference basis of classification , staging , treatment plan , and evaluation therapy effect .
fdg pet / ct not only provides the characteristics of lesions in ct scan , but also finding the lesions activity fdg uptake .
previous reports of lch in fdg pet / ct imaging mostly shows bone , lung , lymph node or skin invasion .
few cases of the primary thyroid lch showed in fdg pet / ct have been reported . in the patient of this case ,
the thyroid involved lch was the first symptoms , and clinical considered as thyroid cancer .
whole - body pet / ct was performed to evaluate the involvement of disease and make an individualized treatment plan after the biopsy pathology .
fdg pet / ct showed bilateral involvement of multiple low - density nodules , the boundary of nodules are clear and some breakthrough thyroid capsule .
fdg uptake was significantly increased in the nodules ; which were mostly higher than primary thyroid cancer in addition to low - differentiated cancer and medullary carcinoma . in ct , these nodules had rare calcification and the density mostly lower than primary thyroid cancer .
however , to confirm all these characteristic performances , needs more patients data accumulation . in summary , we recommend the use of pet / ct as a meaningful noninvasive tool to evaluation scope of lch lesions involving .
 langerhans cell histiocytosis ( lch ) is a rare clonal proliferative disease , with an incidence rate of 4.05.4/1 million individuals . 
 lch encompasses a spectrum of disorders with diverse clinical presentations ranging from a single organ to multiple organ involvement . 
 lch rarely involves the thyroid gland . 
 we presented a case with lch of thyroid gland . 
 the patient had painless progressive neck enlargement and then diabetes insipidus . ultrasonic scan and magnetic resonance imaging scan revealed nodular goiter and pituitary stalk enlargement , respectively . 
 histopathological analysis revealed features of histiocytoid cells . 
 18f - fluorodeoxyglucose ( 18f - fdg ) positron emission tomography / computed tomography ( pet / ct ) was performed in order to rule out the presence of whole body infiltration . 
 18f - fdg pet / ct also demonstrated increased uptake in the thickening pituitary stalk and maxillofacial skin lesion , in addition to the bilateral thyroid nodules , ct showed the left lung nodule and the skull destruction without 18f - fdg uptake . 
 this report emphasizes the role of 18f - fdg pet / ct in multiple organs involvement of patients with lch . 
INTRODUCTION
CASE REPORT
DISCUSSION