This case demonstrates synchronous tumors which are defined as those that occur in the same subject simultaneously.

A biopsy was taken directly from the mediastinal tumor and histopathology reported type B1 thymoma. At the same time a biopsy was performed at left breast, reporting a different primary tumor; carcinoma of the breast lobular subtype.

Different criteria to be considered as synchronous tumors:

• Each tumor must have a defined pattern of malignancy.
• It should be excluded that one constitutes metastasis of another.
• Each tumor must have a different histopathology.
• Each tumor can present with different symptoms or be an incidental finding during the study of the first.