Breed: Labrador Retriever
Gender: MALE, NEUTERED
Suspect systemic mast cell tumor or lymphosarcoma. Located on the ventral neck.
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Throughout the dermis of this ulcerated section of haired skin, there are extensive, often nodular accumulations of epithelioid macrophages, neutrophils, lymphocytes, plasma cells and multinucleated giant cells. There are numerous, spherical, strongly eosinophilic fungal organisms with a thick, refractile cell wall. These intralesional fungal yeast average 10 microns in diameter (range of 6-15 microns) with a 1 micron, refractile cell wall and an internal basophilic body. These yeast demonstrate broad based budding.
Haired skin: Dermatitis, pyogranulomatous, ulcerative, locally extensive, severe, chronic with intralesional fungal organisms most consistent Blastomyces dermatitidis.
Blastomycosis is caused by the dimorphic fungus Blastomyces dermatitis. The organism is ubiquitous in moist rich soil from the Mississippi and Ohio River valleys, around the great lakes and the same orange River region. Multiple states including the Southeastern, South Central and upper Midwestern states and several Canadian prominences have reported cases. Sporadic cases from Colorado, Texas, Kansas, and Nebraska have also been reported. Inhalation of conidia is than usual routes of infection. Infections may be asymptomatic or may present as acute or chronic pneumonia, or the organisms can cause fatal acute respiratory distress syndrome. In 20 to 40% of the cases, disease has become systemic at the time of diagnosis and there is skin, soft tissue, bone, genitourinary, or central nervous system involvement. Rare cases of skin lesions without lung involvement have been described resulting from direct/traumatic inoculation of the organisms. Blastomyces is more severe in immunocompromised patients and more frequently fatal.
Clin Microbiol Rev. 2011;24(2):247-280.