To Cut or Not To Cut: Boxer with a Bone Lesion

Case: 7-year-old neutered Boxer born and raised in Los Angeles

History: Right thoracic limb lameness of 6 days’ duration

Physical Examination: Grade III/IV right thoracic limb lameness and apparent pain on shoulder palpation. No other significant examination findings

There is a large, lytic, and irregularly proliferative lesion in the proximal-to-middle diaphysis of the right humerus; the zone of transition is gradual. The scapula is not involved. Neoplasia (eg, osteosarcoma) is high on the differential list; infectious diseases (bacterial or fungal, specifically coccidiodomycosis in this geographical location) are also considered.

Should this dog go to surgery?
No!

Outcome: CBC and chemistry results were unremarkable. An ultrasound-guided fine-needle aspirate of the abnormal tissue surrounding the right humerus was performed. Cytologic analysis revealed a marked pyogranulomatous inflammation with reactive bone, which is strongly suggestive of a fungal osteomyelitis; neoplastic cells or infectious agents were not visualized on cytology. Bacterial culture of the humeral aspirate yielded no growth. Fungal serology was positive for Coccidioides immitis (positive IgG antibody, 1:16 IgG titer), resulting in a presumptive diagnosis of coccidioidomycosis. A paired IgG titer was not performed. The patient was treated initially with oral itraconazole and then with IV amphotericin B. He survived for 4 years, but required frequent monitoring of serology titers, treatment with antifungal drugs, and pain management. Over the course of the disease, he developed lesions in the left femur and lung compatible with systemic coccidiodomycosis. He was euthanized for unrelated conditions (splenic mass and hemoabdomen).

Comments: This is an example of a fungal osteomyelitis that could have been misclassified as primary bone neoplasia; amputation is not the treatment of choice. The combination of positive serology, radiographic signs of disease in a patient from an endemic area, and response to therapy can be used to make a presumptive diagnosis if the organism isn't demonstrated. Definitive diagnosis requires demonstration of the organism by cytology, biopsy, or culture.

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