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ABSTRACT:Bone metastases are common but serious complication of aggressive thyroid carcinoma, but calvarial metastasis is relatively uncommon complication of the primary tumor of thyroid gland. We are presenting an unusual case report of large calvarial metastasis which had both intracranial and extra cranial components of a previously diagnosed and operated case of follicular carcinoma of thyroid. KEY WORDS: Calvarial metastasis, primary follicular carcinoma of thyroid, skeletal metastasis in thyroid carcinoma. INTRODUCTION:Metastases to the skeletal system from thyroid carcinoma are a well-known event, constituting the second most common systemic site of involvement after lungs. The poor prognosis associated with bone metastases of differentiated thyroid cancer might partly be due to the fact that they are rarely detected at an early stage. Carcinoma of the thyroid gland is one of the possibly curable cancers. At the time of initial diagnosis, 1%-3% of patients with thyroid cancer may have distant metastases, whereas another 7%-23% will develop distant metastases during the disease course 2, 12, 16 .The distant metastases, especially those involving bone, increase mortality rate, compromise quality of life and shorten patient survival.After lung, bone is the most common site of systemic metastasis from thyroid carcinoma 1, 2 , the overall reported incidence ranging from 1% 3 to more than 40% 4 . This incidence varies according to the primary tumour type, with follicular carcinoma showing a much higher frequency than the papillary or anaplastic subtypes in most reported series 1,2,[5][6][7][8] .Approximately 90% of non-medullary thyroid malignancies are well differentiated and are classified as papillary or follicular. Patients with differentiated thyroid carcinoma (DTC) have a high 10-year survival rate (80%-95%), except in the presence of metastatic disease (40% 10-year survival). Incidence of bone metastases is Vertebrae (54%), Pelvis (50%), Ribs (31%), Femur (21%), Skull (13%) and Humérus (11%).Among the different histologic subtypes, follicular carcinoma is most likely to show bone metastases, with reported incidences ranging from 7% to approximately 28%. The poor prognosis associated with bone metastases of differentiated thyroid cancer might partly be due to the fact that they are rarely detected at an early stage. The influence of the microscopic tumor type and tumor differentiation on survival after bone metastasis primarily appears to be due to the much worse prognosis among anaplastic and medullary carcinomas. Age at diagnosis of bone metastases does not influence survivals.

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