RESUMO
SMARCB1/integrase interactor (INI)-1 is one of the core subunit proteins of the ATP-dependent SWI/SNF chromatin remodeling complex and acts as a tumor suppressor. INI-1 loss can be easily assessed using immunohistochemistry and is an important diagnostic clue for a histopathologist. Chordoma is a malignant tumor commonly occurring in the sacrococcygeal spine of adults and is characterized by nuclear expression of brachyury. Poorly differentiated chordoma, a morphologically and molecularly distinct entity, also shows nuclear brachyury positivity along with INI-1 loss. It usually occurs in children and has a predilection to involve the base of the skull. We describe a case of a poorly differentiated chordoma in a 5-year-old girl and discuss its unusual histomorphologic and immunohistochemical features.