The Clival Chordoma Histology Explained
The Clival Chordoma Histology Explained The clival chordoma is a rare and intriguing tumor that arises from remnants of the notochord, a structure pivotal during embryonic development. Located at the skull base, specifically in the clivus region, these tumors often pose diagnostic and therapeutic challenges due to their aggressive nature and complex location. A fundamental understanding of their histology—the microscopic structure and cellular makeup—is essential for accurate diagnosis, prognosis, and treatment planning.
Histologically, clival chordomas are characterized by distinctive features that set them apart from other skull base tumors. They typically exhibit a lobular architecture, with tumor cells arranged in cords, nests, or sheets within a myxoid (mucoid-rich) stroma. This extracellular matrix is abundant in mucopolysaccharides, giving the tumor a gelatinous appearance under the microscope. The tumor cells themselves are often epithelioid or physaliphorous, a term derived from Greek meaning “bubble-bearing,” which describes the appearance of their cytoplasm.
Physaliphorous cells are large, with bubbly, vacuolated cytoplasm that contains mucin. These cells have small, round to oval nuclei that are often centrally located and may display mild nuclear atypia. The vacuolization results from glycogen and mucopolysaccharide content, which can be highlighted using special histochemical stains such as mucicarmine or Alcian blue. This distinctive cellular morphology is a hallmark of chordoma and is critical for differentiating it from other neoplasms.
Immunohistochemistry further supports the diagnosis by revealing specific protein expression patterns. Chordoma cells typically express brachyury, a transcription factor that is a highly sensitive and specific marker for notochordal origin. They also often stain positive for cytokeratins, epithelial membrane antigen (EMA), and S-100
protein. These immunoprofiles help distinguish chordomas from chondrosarcomas, metastases, or other tumors at the skull base that may appear similar histologically.
The variation within chordoma histology is also noteworthy. Conventional or classic chordomas display the aforementioned physaliphorous cells within a myxoid matrix. There are also variants such as chondroid chordomas, which contain cartilaginous components, and dedifferentiated or poorly differentiated chordomas, which exhibit more aggressive features and a less characteristic cellular appearance. Understanding these subtypes is vital because they influence prognosis and treatment approaches.
From a clinical perspective, the histological features of clival chordomas correlate with their biological behavior. The abundance of mucinous material and physaliphorous cells reflects their slow-growing but locally invasive nature. Despite their relatively indolent growth, these tumors often recur after treatment due to their infiltrative pattern and difficulty in achieving complete surgical resection, underscoring the importance of precise histopathological diagnosis.
In conclusion, the histology of clival chordomas reveals a unique combination of cellular morphology, extracellular matrix, and immunohistochemical expression that collectively define this rare tumor. Recognizing these features is crucial for accurate diagnosis, guiding surgical and adjunctive therapies, and understanding the tumor’s potential behavior and prognosis.
