Colonic T-cell–rich, large B-cell lymphoma associated with equid herpesvirus 5 infection and secondary trans-colonic fistula in a horse

Abstract

A 17-y-old Rocky Mountain gelding was presented to the Virginia-Maryland Veterinary Teaching Hospital because of a 4-wk history of anorexia, weight loss, lethargy, and fever of unknown origin. Abdominal ultrasound revealed lymphadenomegaly of the abdominal and colonic lymph nodes, thickening of the wall of the large colon, and a mass associated with the large colon. The horse was euthanized given a poor prognosis. On autopsy, an ~20-cm diameter mass was found within the mesocolon between the right ventral and right dorsal colon. The mass had invaded through the colonic walls and formed a fistula between the 2 involved lumina. On histologic evaluation, the mass consisted of small numbers of large neoplastic lymphocytes, numerous small lymphocytes, and many foamy macrophages. A diagnosis of T-cell–rich, large B-cell lymphoma was made based on immunohistochemical staining for CD79a, CD3, and Iba1; concurrent infection with equid herpesvirus 5 was confirmed with in-situ hybridization (ISH). To our knowledge, neither a trans-colonic fistula resulting from alimentary lymphoma in a horse nor detection of intralesional equid herpesvirus 5 in equine alimentary lymphoma by ISH has been reported previously.

In situ hybridization to detect Escherichia coli in canine granulomatous colitis

“…ISH was performed at the AHDC using a standard protocol and an automated ISH research platform (Discovery Ultra; Roche). 1 After deparaffinization and target retrieval (760-248, mRNA sample prep kit; Roche), 4-μm tissue sections mounted on charged slides were hybridized with 200 μL of ISH probe (433299, RNAscope 2.5 VS Probe- B- E. coli -16SrRNA [ Escherichia coli KLY complete genome 16S ribosomal RNA]; ACD). This was followed by signal amplification (760-236, mRNA RED probe amplification kit; Roche), detection (760-234, mRNA RED detection kit; Roche), and counterstaining with hematoxylin.…”