Answer: Mite, most likely Dermatophagoides species (dust mite).
As mentioned by several readers, we are lacking sufficient details to make a definitive identification. However, we can conclude that this is a contaminant in this specimen and not a cause of the patient's symptoms. As Blaine mentioned, this is a "Conta-mite-nt"!
Some readers mentioned that Sarcoptes scabei should be considered. While this is also a mite, its distinctive features, including its short legs and overall body shape, allow for differentiation from Dermatophagoides:
Thanks again to Dr. Ness and her lab for donating this case.