Patient description: A 58-year-old nonsmoker white female with mild exertional dyspnea and occasional cough is found to have a left lung mass on chest x-ray. She is otherwise asymptomatic. A neurologic examination is unremarkable, but a CT scan of the head shows a solitary mass in the right frontal lobe.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Metastatic Anaplastic/Undifferentiated Thyroid Cancer Locally Advanced Anaplastic/Undifferentiated Thyroid Cancer Histologically or cytologically confirmed diagnosis of anaplastic thyroid cancer or undifferentiated thyroid cancer that demonstrates mutation in the ALK gene as assessed by sequencing of the tumor specimen for Arm A. Other ALK abnormalities as detected by the approved FISH test (Abbott Molecular Inc), using Vysis breakapart probes (defined as 15% or more positive tumor cells); or the Ventana IHC test will also be seen as evidence of ALK abnormality and meeting requirement Patients will not have any other curative therapeutic option, such as radiation or surgery WHO performance status 0-2 Age greater then or equal to 18 years Patients must have recovered from all toxicities related to prior anticancer therapies to ≤ Grade 2 (CTCAE v 4.03), provided that any concomitant medication is given prior to initiation of treatment with ceritinib. Exception to this criterion: patients with any grade of alopecia are allowed to enter the treatment Adequate organ function: the following laboratory have been met Absolute neutrophil count (ANC) greater then or equal to 1.5 x 109/L Hemoglobin (Hgb) ≥ 8 g/dL Platelets greater then or equal to 75 x 109/L Serum total bilirubin ≤ 1.5 x upper limit of normal (ULN), except for patients with Gilbert's syndrome who may be included if total bilirubin ≤ 3.0 x ULN and direct bilirubin ≤ 1.5 x ULN  Patients eligible must not meet any of the following Patients with known hypersensitivity to any of the excipients of ceritinib (microcrystalline cellulose, mannitol, crospovidone, colloidal silicon dioxide and magnesium stearate) Patients with symptomatic CNS metastases who are neurologically unstable or have required increasing doses of steroids within the 1 week prior to study entry to manage CNS symptoms Prior therapy with ceritinib Presence or history of a malignant disease other than thyroid cancer that has been diagnosed and/or required therapy within the past year and is undergoing active anticancer treatment. Exceptions to this the following: completely resected basal cell and squamous cell skin cancers, and completely resected carcinoma in situ of any type Patients with known history of extensive disseminated bilateral interstitial fibrosis or interstitial lung disease, including a history of pneumonitis, hypersensitivity pneumonitis, interstitial pneumonia, obliterative bronchiolitis, and clinically significant radiation pneumonitis (i.e. affecting activities of daily living or requiring therapeutic intervention) Patient has clinically significant, uncontrolled heart disease and/or recent cardiac event (within 6 months), such as unstable angina within 6 months prior to screening myocardial infarction within 6 months prior to screening history of documented congestive heart failure (New York Heart Association functional classification III-IV)