Chordoma cutis

Chordoma Cutis - A Diagnosis not to be Missed

Chordomas are rare midline tumors of the bone usually arising from sacrum, skull bones and spine, close to neuraxis. However an extensive involvement of the soft tissues can simulate a soft tissue subcutaneous tumour of the gluteal region -a presentation called chordoma cutis. Our patient presented with a gluteal mass and a trucut biopsy was done suspecting a soft tissue tumour. The hematoxylin and eosin stained section of the biopsy closely simulated a lipomatous tumour. However, on closer inspection the clear cells were found to have very fine vacuolations.The usual myxoid background and characteristic physaliferous cells seen in chordomas were not seen. Still a differential of chordoma was entertained in view of the site and age of the patient. Immunohistochemistry for cytokeratin and S-100 was performed and both were unambiguously positive. On literature search, we came across a soft tissue tumour called parachordoma which mimics chordoma both morphologically and immunohistochemically and has also been reported in the gluteal region. An MRI was performed which showed the tumour to be arising from the sacrum and secondarily involving the gluteal soft tissues. This case highlights the importance of considering chordoma in the differential diagnosis of gluteal masses with clear cell morphology even in the absence of physaliferous cells and myxoid background before signing them out as lipomatous tumours.