 Muffin, an 8-year-old female Rottie, presents with a two-week history of right front leg lameness. The physical exam is within normal limits except for a firm mass on the distal forearm, which is painful on palpation. You suspect a tumor.
How would you approach this case? What are your rule-outs?  | | A: A suspicious lesion in the right radius of Muffin, an 8-year-old female Rottie. Photo by Dr. Phil Zeltzman | Radiographs of the distal radius and ulna are the next logical step. They reveal a lytic and proliferative lesion with soft-tissue swelling (see photo A). Malignant long bone tumors include osteosarcoma (about 85 percent of the time), chondrosarcoma (5 percent), fibrosarcoma (5 percent) and hemangiosarcoma (5 percent). There is a small chance of a metastatic lesion. If this were a benign lesion, it could be an osteoma, chondroma or bone cyst. It also could be osteomyelitis from a bacterial or fungal infection. Euthanasia offered as a sole treatment option is not ethically acceptable and medically recommended in 2010. Primary bone cancer is a treatable condition that requires a thorough work-up before irreversible decisions are made. A standard work-up should include: - CBC and chemistry. An increased alkaline phosphatase may be correlated with a poorer prognosis in cases of osteosarcoma. (See JAVMA, 1998, Vol. 213.)
- Three views of the thorax, to detect visible metastasis (macro-metastasis).
- A bone biopsy.
- Fungal and bacterial cultures of the bone.
The timing of bone biopsy is debatable. If the clinician is convinced that the lesion is consistent with osteosarcoma, or if the client has financial constraints, an open discussion should take place about the pros and cons of performing an amputation without the benefit of a prior biopsy. If amputation is elected, then a biopsy and cultures should be harvested afterward to confirm the suspicion. This is a huge leap of faith for the client, so it is important to document what was discussed and what the client chose. How It’s Done Should a biopsy be preferred first, then the surgery site is shaved, scrubbed and draped. A stab incision is performed in the skin. A hemostat or periosteal elevator is used to approach the bone. Several cores of bone are sampled with a Jamshidi needle (see photo B) or a Michelle trephine. It is prudent to use the smallest needle possible to decrease the chances of a pathological fracture of the bone. This is why most surgeons prefer Jamshidi needles. They are available from a variety of manufacturers. A 4-inch, 8 to 11 G needle is often used. The needle and its sharp stylet are placed on the bone and a small indentation is made. The stylet is removed, and cores of bone are harvested using a rotational motion in various directions. The first cortex and the entire medullary cavity are biopsied. Maintain Bone’s Strength  | | B: Bone biopsy with a Jamshidi needle in a 4-year-old Labrador with osteo... | | 
