Chordomas are rare tumors that can be a challenge to diagnose.
Situations associated with difficult diagnosis:
(1) occurrence of primary tumor at a site other than sacrococcygeal, spheno-occipital or vertebral regions
(2) metastasis from silent primary
(3) inadequate biopsy specimen
(4) when associated with tuberous sclerosis complex
(5) poorly differentiated tumors with few vacuolated cells
Differential diagnosis:
(1) chondrosarcoma
(2) metastatic renal cell carcinoma
(3) salivary gland carcinoma
(4) metastatic adenocarcinoma
(5) liposarcoma
Immunohistochemical features that can be helpful in diagnosis:
(1) EMA positive
(2) S100 variable
(3) cytokeratins (CK8, CK19, CK18, pankeratin) positive
(4) brachyury positive (useful)
(5) vimentin positive
(6) podoplanin negative
(7) INI negative
