Kir7.1 immunoreactivity in canine choroid plexus tumors

Abstract

Abstract. Choroid plexus neoplasms are uncommon brain tumors in dogs. Choroid plexus carcinomas often spread diffusely throughout the ventricular system and subarachnoid space and, in aggressive forms, can mimic histologic patterns of other carcinomas, including being embedded in a desmoplastic reaction. Although choroid plexus tumors (CPTs) heterogeneously express pan-cytokeratin, little is known about other markers to identify choroid plexus and their associated tumors. Kir7.1, an inward-rectifier potassium channel, is reported to have high diagnostic utility in human neuropathology to distinguish CPTs from other primary brain tumors and cerebral metastases. To determine Kir7.1 expression in the dog brain, we analyzed the immunoreactivity of Kir7.1 in normal brain, gliomas, ependymomas, CPTs, meningiomas, and carcinomas. In normal brain tissue, the immunostaining was restricted to the choroid plexus where there was robust membrane immunoreactivity along the apical border of the cells with less intense cytoplasmic staining. Similar strong immunoreactivity was detected in 12 of 12 CPTs, whereas 5 of 5 gliomas, 4 of 5 ependymomas, 5 of 5 meningiomas, and 5 of 6 carcinomas had no immunoreactivity. One ependymoma and 1 nasal carcinoma with squamous metaplasia were up to 75% immunopositive, with moderate cytoplasmic and membranous immunoreactivity, but lacking the robust apical immunoreactivity pattern. Analysis for immunoreactivity in a tissue microarray failed to yield any other locations in which immunoreactivity was detected. These results, including the distinctive pattern of immunostaining in CPTs, suggest that Kir7.1 is an excellent marker for CPTs in the dog.

Clinicopathologic Features, Diagnosis, and Characterization of the Immune Cell Population in Canine Choroid Plexus Tumors

“…As observed in the current study, CPTs are uncommon in dogs (7), representing only 0.19% of 5,680 canine necropsies submitted to our diagnostic service between 2005 and 2018. In contrast to human CPTs, which are primarily pediatric neoplasms, canine CPTs occur mainly in middle-aged to older individuals (2, 6, 7, 15), as corroborated by the current dataset.…”

“…Cases of CPT in dogs were retrospectively identified at the Athens Veterinary Diagnostic Laboratory database between 2005 and 2018. Selected cases were reviewed, archived glass slides were examined, and replicate tissue sections were immunostained with inward rectifier potassium channel Kir7.1 for diagnostic confirmation (15). A detailed histological evaluation of all confirmed cases was performed, and tumors were characterized according to the 2016 WHO Classification of Tumors of the Central Nervous System (1).…”

“…In veterinary medicine, CPTs occur predominantly in dogs (5–7) and are rare to unreported in other species (5–14). In dogs, CPTs account for 10% of all primary central nervous system (CNS) neoplasms (7), occurring mainly in middle-aged to older individuals (2, 6, 7, 15). Magnetic resonance imaging has been shown to be useful in the clinical diagnosis of intraventricular masses, but diagnostic confirmation of a CPT relies heavily on histology and immunohistochemistry (IHC) (6, 7, 15).…”

Glomeruloid Microvascular Proliferation, Desmoplasia, and High Proliferative Index as Potential Indicators of High Grade Canine Choroid Plexus Tumors

“…These data are in line with a recent report on canine CPT 20 and parallel human CPT data showing that the Ki-67 PI is an important prognostic indicator associated with the aggressiveness of human CPT, response to treatment, and clinical outcome. 6,7,23,28,32 Additionally, desmoplasia and GMVP were observed clearly more frequent in CPC than CPP, suggesting that these 3 features could be included in the histological grading system as criteria for malignancy in CPT. Indeed, we found an association between GMVP and brain invasion suggesting that GMVP occurs in tumors with more aggressive behavior but not between GMVP and spread within the CSF spaces.…”

“…In animals, these tumors occur most commonly in dogs and account for approximately 10% of all canine primary brain tumors. 10 Due to their histological similarity to the human counterpart, in the current literature, canine CPT 7,10,17,20,24,31 are frequently graded in analogy to the human WHO current classification of central nervous system (CNS) tumors 14 into choroid plexus papilloma (CPP, grade I), atypical choroid plexus papilloma (aCPP, grade II), and choroid plexus carcinoma (CPC, grade III). 31 In humans, CPC is a highly aggressive malignant tumor compared to CPP and aCPP, and tumor grade currently dictates the use of appropriate treatment modalities.…”