hidradenomas are benign cutaneous tumors of sweat gland origin , with the clear cell type constituting the most frequent histologic variety . usually , they are diagnosed in the elderly population , the peak incidence being the fifth to sixth decade .
we describe a young girl , in whom nodular hidradenoma developed at the age of 6 years .
hence , our case demonstrates that nodular hidradenoma is a rare differential diagnosis of skin tumors , even in the pediatric age group .
a 10-year - old girl presented to us with a swelling on the left thigh , which had been progressively enlarging over the preceding 4 years .
cutaneous examination revealed a solitary erythematous dome - shaped , well - circumscribed tumor , measuring approximately 6 cm  4.5 cm .
there was spontaneous dripping of straw - colored serous fluid at the rate of 2030 drops / min , the discharge accentuating on pressure .
biochemical analysis of the serous fluid revealed glucose 25 mg / dl , protein 4 g / dl , sodium 131 mmol / l , and potassium 4.3 mmol / l , almost similar to that of serum , the low concentration of glucose compelling us to think of something else . the mass was excised .
the solid portion was largely composed of a cell type having finely granular , faintly eosinophilic cytoplasm with a dark - colored round to oval nucleus .
the cyst was lined by a single layer of cuboidal epithelium without evidence of decapitation secretion [ figure 5 ] .
solitary dome - shaped , well - circumscribed tumor over the left thigh photomicrograph showing a well - encapsulated mass composed of solid and cystic portions ( h and e , 40 ) photomicrograph showing a well - encapsulated mass with large cystic spaces within it .
ductal luminal structures can be appreciated ( h and e , 100 ) photomicrograph showing clear cells in the center along with cystic spaces ( h and e , 400 ) note the large cystic cavity within the mass .
clear cell hidradenoma or eccrine acrospiroma of the skin was first described by liu , in 1949 , as clear cell papillary carcinoma of the skin .
it was reported under various designations such as nodular hidradenoma , eccrine acrospiroma , solid - cystic hidradenoma , clear cell acrospiroma , clear cell myoepithelioma , and eccrine sweat gland adenoma .
clinically , nodular hidradenoma presents as a slow - growing , red- , blue- , or brown - colored solitary , 530 mm in size , freely mobile and firm nodule , with an occasional cystic appearance .
these are most commonly found on the scalp , face , thorax , abdomen , and gluteal region .
this tumor is found mainly in adults and is excised more commonly in women than in men .
our patient was a young girl who presented with a gradually increasing swelling on the lower limb , a site that is unusual for the development of nodular hidradenoma .
literature search showed very few cases of nodular hidradenoma on the lower limb , that too in the pediatric age group .
however , a case of nodular hidradenoma masquerading as umbilical polyp has been reported in a 1-year - old male child
our patient complained of serous discharge from the lesion , for the preceding 3 months .
clinical differential diagnoses for our case were cutaneous lymphoma , dermatofibrosarcoma protuberans , epidermoid cyst , and sweat gland tumor . however , histology reliably excluded all the possibilities .
it was predominantly composed of a cell type having finely granular , faintly eosinophilic cytoplasm with a dark - colored round to oval nucleus .
the chronically discharging nature of the tumor in our patient was attributable to the fluid - filled cavity within the lesion .
biochemical analysis of the fluid was almost consistent with that of serum , however , the low concentration of glucose hinted that it might be normal sweat .
recently , nuclear grooving has been described as a useful morphological feature to aid in its diagnosis .
immunohistochemical staining of the tumor cells demonstrates positive staining with antibodies against ck - cam 5.2 , ber - ep4 , p63 , epithelial membrane antigen , s-100 protein , smooth muscle actin , and vimentin .
however , due to unavailability of resources and financial constraints , the immunohistochemical analysis could not be performed in our case .
the high rate of local recurrence ( 10% ) and potential for malignant transformation make surgical removal with wide margins as the widely accepted modality of treatment .
the high recurrence is attributable to incomplete resection and to tumor tissue located between the dermis and subcutaneous tissue .
these are characterized by increased mitotic activity , angiolymphatic invasion , local extension into deeper tissues , and a dispersed pattern of growth .
nodular hidradenoma in the pediatric age group is extremely rareit is usually located over the head , neck , and trunk . in our case ,
the lesion was present in the lower limbthe presence of an unusually large cystic cavity within the tumoral mass , leading to serous discharge , makes our case even more interesting . 
 
nodular hidradenoma in the pediatric age group is extremely rare it is usually located over the head , neck , and trunk . in our case ,
the lesion was present in the lower limb the presence of an unusually large cystic cavity within the tumoral mass , leading to serous discharge , makes our case even more interesting .
nodular hidradenoma in the pediatric age group is extremely rareit is usually located over the head , neck , and trunk . in our case ,
the lesion was present in the lower limbthe presence of an unusually large cystic cavity within the tumoral mass , leading to serous discharge , makes our case even more interesting . 
 
nodular hidradenoma in the pediatric age group is extremely rare it is usually located over the head , neck , and trunk . in our case ,
the lesion was present in the lower limb the presence of an unusually large cystic cavity within the tumoral mass , leading to serous discharge , makes our case even more interesting .
nodular hidradenoma in the pediatric age group is extremely rareit is usually located over the head , neck , and trunk . in our case ,
the lesion was present in the lower limbthe presence of an unusually large cystic cavity within the tumoral mass , leading to serous discharge , makes our case even more interesting . 
 
nodular hidradenoma in the pediatric age group is extremely rare it is usually located over the head , neck , and trunk . in our case ,
the lesion was present in the lower limb the presence of an unusually large cystic cavity within the tumoral mass , leading to serous discharge , makes our case even more interesting .
 a 10-year - old girl presented with a swelling on her left thigh that was associated with dripping of serous fluid from the lesion . based on histological features of the excised tumor , a diagnosis of nodular hidradenoma was made . 
 atypical features including large size of the tumor , location on the lower limb , a weeping presentation , and histological finding of a nodular hidradenoma with an unusually large cystic cavity discharging fluid prompted us to report the case . 
Introduction
Case Report
Discussion
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