Goiter or thyroid hypertrophy, can in some cases extend toward the mediastinum, and in rare cases grow to massive sizes. Ever since the first description of substernal goiter, many approaches have been suggested, however definitive treatment ultimately comes to surgery. Thyroid cancer within a substernal goiter can be quite challenging since cancer foci locations and technical difficulties could make the correct diagnosis more difficult. We report a case of a giant substernal goiter that was detected on a young patient. It compromised the superior mediastinum and pleura. After surgery, patient fully recovered. However, a hidden papillary thyroid cancer was found within the goiter. Thyroid disease has difficult scenarios, and when goiter is associated with cancer can make the clinical situation even more complex. One of the most valuable things in thyroid disease associated with cancer is that if detected in the early stages it can be cured. Timely diagnosis and treatment should be a vital part of thyroid disease.

Keywords: Cancer, Goiter, Substernal goiter, Thyroid