7 February 2008 – Case of the Week #110
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We thank Dr. Mike McCormick, Holy Family Memorial Hospital, Wisconsin (USA), for contributing this case. To contribute a Case of the Week, email NatPernick@Hotmail.com with the clinical history, your diagnosis and microscopic images in JPG, GIF or TIFF format (send as attachments, we will shrink if necessary). Please include any other images (gross, immunostains, etc.) that may be helpful or interesting. We will write the discussion (unless you want to), list you as the contributor, and send you $35 (US dollars) for your time after we send out the case. Please only send cases with a definitive diagnosis, and preferably cases that are out of the ordinary.
Case of the Week #110
A healthy 47 year old Caucasian man presented to his family physician after a slip and fall in his hot tub for persistent pain in the low back area. A routine lumbosacral radiograph showed a fractured coccyx and a subtle, ill-defined lucency involving the sacrum and coccyx. The clinical impression was an infected pilonidal cyst, and the patient received antibiotics. Due to increasing pain, he consulted a general surgeon, who found induration and tenderness along the inner gluteal fold extending into the gluteal cleft. There was no drainage or punctum. The surgeon excised a small wedge of tissue.
What is your diagnosis?
The surgeon was skeptical of the diagnosis, and ordered an MRI (sagittal MRI), which revealed a large mass consistent with chordoma.
This case has the classic features of chordoma. It is a rare, slow growing but malignant midline bone tumor that may arise from intraosseous benign notochordal cell tumors (AJSP 2007;31:1573, Mod Path 2005;18:1005). It usually affects the sacrococcygeal region in adults, the spheno-occipital region in children, or the thoracolumbar spine.
Grossly, it is soft, gelatinous and hemorrhagic. Histologically, it is characterized by cords and lobules of physaliferous cells (having bubbles or vacuoles) separated by a fibrous septa, with an extensive myxoid stroma. The physaliferous cells are often large, with vacuolated cytoplasm and a prominent vesicular nucleus (Archives 2004;128:1457). There may also be smaller tumor cells with a small nucleus.
The tumor cells are immunoreactive for keratin (CK 8/18, CK19, AE1-AE3), EMA and S100, and negative for CK7 and CK20. They are occasionally focally positive for synaptophysin, but not chromogranin (Hum Path 1998;29:119). The myxoid stroma is reactive with Alcian blue.
The differential diagnosis includes metastatic renal cell carcinoma (prominent vascularity, no lobulation) and chondrosarcoma (not midline, no fibrous septa, keratin negative).
Treatment includes aggressive surgery, often leading to long survival (Oncologist 2007;12:1344). In children, external radiation is often successful for base of skull tumors (AJSP 2006;30:811). Some tumors may dedifferentiate to high grade spindle cell sarcomas.
Nat Pernick, M.D., President
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