# Case Report: Histochemical and immunohistochemical characterization of a canine giant cell bone tumor in lumbar spine

## TL;DR

A 10-year-old Poodle was diagnosed with a rare bone tumor in the lumbar spine, confirmed through histological and immunohistochemical analysis.

## Contribution

This case report provides a detailed characterization of a canine giant cell tumor in the lumbar spine using histochemical and immunohistochemical methods.

## Key findings

- The tumor contained multinucleated giant cells positive for TRAP and lysozyme.
- Mononuclear cells expressed alpha smooth muscle actin and IBA-1 highlighted histiocytic cells.
- The tumor was diagnosed as a primary lumbar extradural giant cell tumor of bone.

## Abstract

A 10-year-old sexually intact male Poodle dog, weighing 14 kg, was referred with abnormal gait (ataxia) and antalgic posture. The dog had a medical history of previous trauma and prostatitis diagnosed six months ago. Serum biochemical analysis showed elevated alkaline phosphatase and alanine aminotransferase levels. Neurological examination revealed hind limb dragging, body tilt, delayed proprioception—particularly affecting the left hind limb—and pain upon palpation of the lumbar region. Imaging diagnostic made evident a mass and a significant osteolysis of the second lumbar vertebra (L2), particularly on the left side of the vertebral body, extending into the first (L1) and third (L3) lumbar vertebrae. Necropsy findings confirmed the presence of a nodular soft mass below the left kidney and a firm mass compressing the medullary canal at L1-L3. Both masses exhibited whitish areas interspersed with blood-filled spaces. The tumor comprised numerous multinucleated giant cells of the osteoclastic type (positive for tartrate-resistant acid phosphatase- TRAP- and lysozyme), evenly distributed among mononuclear cells (both rounded and spindle-shaped). Alpha smooth muscle actin (SMA) was expressed in mononuclear cells, while IBA-1 staining highlighted mononuclear histiocytic cells. The final diagnosis was a primary lumbar extradural giant cell tumor of bone.