An 11-year-old, MI Labrador retriever presented due to a non-healing wound on the left hind foot that progressed over about one month to the other hind leg and the nose. The dog has been previously diagnosed with atopic dermatitis and cutaneous adverse food reaction. He is on long term cyclosporine modified and prednisolone with additional short term medications including gabapentin, proviable, metronidazole, omeprazole, and cefpodoxime. The patient resides in Texas and does not have an extensive travel history. A superficial aerobic culture was performed before the biopsy and identified a few Staphylococcus epidermidis colonies.
Figure 1: Left hind paw and lateral limb lesions.
Figure 2: Left hindlimb medial lesion.
Figure 3: Nasal philtrum lesion.
Figure 4: Magnification at 2x.
Figure 5: Magnification at 20x.
Figure 6: Magnification at 40x.
Figure 7: Fontana Masson stain. Magnification at 20x.
March 2023 - What is the most likely diagnosis?