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Clinical Summary

A 46-year-old male presented with persistent pain in the lower back region. The pain was dull, progressive, and associated with mild difficulty in walking. MRI revealed a lobulated mass in the sacrococcygeal region, suggestive of a neoplastic lesion with possible bone erosion.

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Gross Pathology

The excised specimen showed a lobulated, gelatinous, gray-white tumor involving bone and adjacent soft tissue. The cut surface appeared translucent and mucoid in texture.

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Microscopy Findings

Low Power View:
The tumor is composed of lobules separated by fibrous septa. Each lobule contains tumor cells embedded in a myxoid stroma.

Intermediate Power:
Within the lobules, tumor cells are arranged in cords, nests, and sheets. The cells have abundant bubbly (vacuolated) cytoplasm, giving rise to the classic physaliphorous appearance.

High Power View:
Cells show round to oval nuclei with mild pleomorphism, and the background matrix is myxoid. Occasional mitoses may be seen, but necrosis is uncommon.

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Immunohistochemistry

The tumor cells are typically positive for:

• Cytokeratin (AE1/AE3)
• EMA
• S100
• Brachyury (nuclear positivity) – a key diagnostic marker for chordoma.

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Diagnosis:

Chordoma (Conventional Type) – arising from the sacrococcygeal region.

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Types of Chordoma

Chordoma is a malignant bone tumor derived from notochordal remnants. It mainly affects the axial skeleton — especially the sacrum, skull base (clivus), and vertebral column.
Histologically, there are three main subtypes:

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1. Conventional (Classic) Chordoma

• Most common variant (~70% of cases).
• Shows lobular architecture with fibrous septae.
• Cells: Physaliphorous (bubble-bearing) cells with vacuolated cytoplasm.
• Matrix: Myxoid stroma.
• IHC: Positive for cytokeratin, EMA, S100, brachyury.
• Location: Sacrococcygeal region > clivus > vertebral column.

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2. Chondroid Chordoma

• Intermediate features between chordoma and chondrosarcoma.
• Matrix: More chondroid (cartilage-like) areas.
• Better prognosis than conventional chordoma.
• IHC: Brachyury positive (helps distinguish from chondrosarcoma).
• Often seen in the skull base.

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3. Dedifferentiated Chordoma

• Aggressive variant with poor prognosis.
• Contains areas of high-grade sarcoma (spindle cells, atypia, mitoses).
• May arise de novo or from recurrent classic chordoma.
• IHC: Loss of brachyury expression in the dedifferentiated areas.

Discussion:

Chordomas are rare malignant tumors of notochordal origin, most commonly found in the sacrum and clivus. They occur in adults between 30–60 years of age and often present with pain or neurological symptoms due to local invasion.

Histologically, they are characterized by physaliphorous cells within a myxoid matrix, arranged in lobules separated by fibrous septa. Differentiation from chondrosarcoma is important, and Brachyury staining helps confirm the diagnosis.

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Key Takeaways:

• Chordoma originates from notochordal remnants.
• Common site: Sacrococcygeal region.
• Characteristic feature: Physaliphorous cells with vacuolated cytoplasm.
• Immunoprofile: Cytokeratin+, EMA+, S100+, Brachyury+.
• Management: Wide surgical excision with or without radiotherapy.

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