Age: 2 Y
Gender: FEMALE, SPAYED
Rule out neoplasia. Right dorsal ear.
Click here for the IDEXX Pathology Report on this case.
Haired skin: There is a regionally extensive dermal and subcutaneous mass comprised of sheets of macrophages with associated neutrophils, lymphocytes and plasma cells.
Haired skin: Dermatitis and cellulitis, regionally extensive, granulomatous, suppurative and lymphoplasmacytic, marked, subacute
The lesion is separated from the closest lateral surgical margin by less than 1 mm and extends to the deep tissue margin.
Special stains: (1) GMS: No etiologic agents are note; (2) Fite’s: Intrahistiocytic acid fast bacilli noted, consistent with Mycobacterium spp.
Canine leproid granuloma is a pyogranulomatous mycobacterial disease of the subcutis and skin caused by novel and as yet unnamed Mycobacterium sp. An opportunistic, or atypical, mycobacterial species is most likely. Short coated breeds account for over 90% of affected dogs with either Boxers or Boxer cross breeds accounting for half of the reported cases. The pinnae and distal legs are common sites. Cutaneous infections are often acquired from the environment following trauma such as bite or fight wounds, abrasions, and puncture wounds. Lesion development typically occurs slowly over a period of weeks to months. The clinical course is typically prolonged, and lesions include single or multiple cutaneous and subcutaneous nodules, plaques, purpuric macules, or diffuse swellings. Fistulous tracts may develop. Regional lymph nodes may become enlarged. Despite extensive, cutaneous involvement, affected animals usually remain active and normal and exhibit no systemic signs. The disease is commonly self-limiting in immunocompetent dogs, and spontaneous regression is common. Evaluation for systemic disease, though, is warranted. Additionally, bacterial culture is highly recommended to rule out other Mycobacterial species which may pose a zoonotic threat.
Vet Pathol 2002, 39:234-9; Vet Dermatol 2012, 23(6):465-488; Muller & Kirk’s Small Animal Dermatology, 7th Ed., pp. 210-211, 2013
Image 1: Low magnification view of the lesion (as submitted), demonstrating an inflammatory nodule in the dermis.
Image 2: Higher magnification view demonstrating the macrophages that make up the inflammatory nodule.
Image 3: Higher magnification view demonstrating intracellular slender acid fast bacilli via Fite’s staining.