papillary thyroid carcinoma ( ptc ) is the most frequent type of thyroid malignancy , and the usual metastasis sites include the locoregional lymph nodes .
distant metastasis of ptc is rare and usually involves the lungs , liver , bones and brain .
the skin metastasis of ptc is a very rare condition , and the scalp is the most frequent cutaneous area which is involved .
other cutaneous areas that are involved with less frequency are the cheeks , shoulders , arms , abdomen and thighs .
a 64 year - old female with past medical history of metastatic papillary thyroid carcinoma ( ptc ) with both liver and lung metastasis presented with a 2.5  3 cm erythematous tender nodule in right parietal scalp of two months duration .
she had a past medical history of total thyroidectomy and also had received repeated doses of radioactive iodine ( rai ) therapy in the past two years .
her last dose of rai131 ( 200 mci ) was three weeks prior to the time of presentation .
she also had a history of subglottic mass as a result of thyroidal carcinoma involvement with severe tracheal stenosis , and had undergone tumoral resection and tracheal anastomosis and partial hemilaryngectomy two years ago because of subglottic involvement by thyroidal carcinoma .
high resolution computed tomography ( hrct ) demonstrated multiple metastatic nodules in both lungs and loculated left side pleural effusion consistent with advanced metastatic involvement .
a differential diagnosis of pillar cyst and metastasis was given by dermatologist for scalp lesion .
histopathologic examination of the lesion revealed skin tissue with tumoral involvement of the dermis composed of numerous follicles ( likely thyroid follicles ) , lined by relatively large cuboidal epithelial cells with round nuclei , fine chromatin pattern , little granular cytoplasm and eosinophilic colloidal material within some of follicles , and mitosis , which was consistent with metastatic thyroidal carcinoma [ figures 1 and 2 ] .
she was discharged with suppressive therapy with levothyroxine and referred to oncology clinic for continuation of the treatment plan .
scalp lesion biopsy showing skin tissue with tumoral infiltration of dermis by numerous follicles ( likely thyroid follicle ) , consistent with metastatic thyroidal carcinoma ( h and e , 40 ) scalp metastasis of thyroidal carcinoma composed of numerous follicles lined by relatively large cuboidal epithelial cells with round nuclei , fine chromatin , little granular cytoplasm and eosinophilic colloid material within some of follicles with mitotic division ( h and e , 400 )
the skin metastasis of ptc is mostly associated with aggressive and disseminated disease and shows a poor outcome .
some authors suggested that the average patient survival time after discovering of skin metastasis is 19 months .
here , we have reported a case of scalp metastasis of ptc in a patient with metastatic pulmonary and liver involvement .
metastasis of thyroid cancer should be considered in the differential diagnosis of scalp tumors in any patient with a history of thyroidal carcinoma ; and , excisional skin biopsy is necessary for confirming the diagnosis .
 the skin metastasis of papillary thyroid carcinoma ( ptc ) is a rare condition and the lesions should be differentiated from primary skin tumors . 
 the scalp is the most frequent site which is involved in skin metastasis of ptc . 
 it shows the poor outcome and aggressive nature of disease . in this report 
 , we aim to present a case report of a 64 year - old female with scalp metastasis of ptc in the context of disseminated pulmonary and liver metastasis . 