April 2013 Case of the Month

Photomicrograph of an aspirate from a mass around the shoulder joint of a dog


Case information

A 6 year old castrated male Schnoodle presented to the Cornell University Hospital for Animals Orthopedic Surgery Service with a several year history of right forelimb lameness that had become progressively worse over the past three months. Over the years, the dog had received non-steroidal anti-inflammatory drugs, tramadol, and pregabalin as needed for pain. The owners reported that his pain was no longer well controlled with this medical management. On presentation, the dog was bright, alert, and responsive and vital signs were within normal limits. The dog was non-weight bearing on the right forelimb and severe muscle atrophy of that limb was noted. A large, firm mass was palpated at the right shoulder joint. The regional lymph nodes (superficial cervical and axillary) were not palpable due to the presence of the mass. The remainder of the physical examination was unremarkable. Results from a CBC were within reference intervals. A mildly increased alkaline phosphatase of 216 U/L (reference interval, 17-111 U/L) was the only abnormality on a biochemical panel and urinalysis was unremarkable. The dog was sedated for radiographs of the right shoulder, which revealed an aggressive bony lesion in the proximal humerus that crossed the joint to include the distal scapula. A fine needle aspirate was performed on the shoulder mass and a Diff-Quik®-stained smear was submitted for cytology (see images below):

  • What are your differential diagnoses for an aggressive bony lesion (regardless of location) on radiographs?
  • Does the aspirate indicate an inflammatory or neoplastic lesion?
  • How would you classify the population of cells in this aspirate: epithelial, mesenchymal, or discrete (round) cell?

Figure 1: Shoulder mass aspirate (Diff-quik®, 100x)
Figure 1: Shoulder mass aspirate (Diff-Quik®, 100x)

Figure 2: Shoulder mass aspirate (Diff-quik®, 500x)
Figure 2: Shoulder mass aspirate (Diff-Quik®, 500x)

Answer on next page

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