In case of a long standing goitre., ca most probable to occur is :
Follicular
Papillary
Anaplastic
Medullary
Ans. is 'a' ie follicular "An increased incidence of cancer (usually follicular) has been reported from endemic areas. Dominant or rapidly growing nodules in longstanding goiters should always be subjected to aspiration cytology." - Bailey & Love
Thyroid Malignancies