A 67‐Year‐Old Man with a Lumbar Spine Lesion

Clinical History

The patient is a 67‐year‐old man with a history of hypertension and coronary artery disease who presented with progressively worsening low back pain for 1 year. He underwent a laminectomy for lumbar spinal stenosis 17 years ago and had done very well after the procedure. Review of systems was negative for weakness as well as bowel or bladder dysfunction. Physical examination revealed normal strength in the upper and lower extremities. Spine films showed lumbar levoscoliosis, multilevel degenerative lumbar disease and lumbar lordosis with normal pelvic tilt. Magnetic resonance imaging (MRI) of the spine showed multilevel degenerative disc disease and an incidental intradural, intramedullary mass at L1–L2 (Figure 1A,B). The radiologic diagnosis was schwannoma, and the differential included ependymoma and neurofibroma. The patient presented to this institution for a second opinion. He chose to undergo surgery for tumor resection.

Figure 1.

 

Microscopic Findings

Intraoperative evaluation demonstrated a benign spindle cell lesion with multiple foci of mineralization. Review of permanent hematoxylin and eosin (H&E) sections showed soft tissue with numerous needle‐shaped crystals arranged radially as a fan and surrounded by a bland population of spindle cells, granulation tissue, mild chronic inflammation and hemosiderin‐laden macrophages (Figure 1C–E). Mitotic figures were inconspicuous. No necrosis was seen. The crystals demonstrated positive birefringence on polarizable light (Figure 1F). What is the diagnosis?

Diagnosis

Tophaceous pseudogout.

Discussion

Tophaceous pseudogout is characterized by deposition of calcium pyrophosphate dihydrate (CPPD) crystals within soft tissue. The condition, which was first described in 1962, appears radiographically as chondrocalcinosis involving hyaline and fibrocartilage 5. Tophaceous pseudogout is most commonly sporadic and shows an association with a variety of conditions, such as prior surgery, trauma, gout, hyperparathyroidism, hypophosphatasia, hypomagnesemia, hemochromatosis and Wilson's disease 3. The appendicular skeleton is most commonly affected, and involvement of the spine is relatively rare in comparison. The proposed mechanism of disease in the spine consists of nodular deposition of CPPD crystals in the ligamentum flavum or atlanto‐occipital ligament, with ensuing myelopathy or cervicomedullary compression 1, 2, 7. The cervical spine is most commonly affected and the thoracic spine is least affected 5, 6. Because the presenting symptoms mimic more common conditions such as spinal stenosis, lumbar radiculopathy, spondylolisthesis or cauda equina syndrome, tophaceous pseudogout is not usually considered at presentation 4, 6. The diagnosis is made by examining the tissue under polarizable light and demonstrating positive birefringence.

In the case of our patient, risk factors included age and remote history of laminectomy for spinal stenosis. The diagnosis was not considered at presentation and was established after histologic examination of the tissue under polarizable light. This case demonstrates involvement of the lumbar spine by tophaceous pseudogout.