Intracranial Granular Cell Tumours in Three Dogs: Atypical Magnetic Resonance Imaging Features and Immunohistochemical Study

Abstract

Intracranial granular cell tumours (GCT) are uncommon neoplasms of uncertain cellular origin that are rarely reported in dogs. This case series describes three aged dogs that presented with neurological signs in which magnetic resonance (MR) imaging revealed plaquelike extra-axial lesions that were hypointense on T2-weighted (T2w) images. The surgical biopsy of the lesions and necropsies were followed by histochemical characterisation with periodic acid–Schiff (PAS) staining and immunohistochemistry with ubiquitin, S-100, and SOX-10 to elucidate the cellular origin. The immunohistochemical study indicated that these intracranial GCTs were not of Schwann cell origin. In conclusion, GCTs should be considered a differential diagnosis of intracranial, extra-axial hypointense brain lesions on T2w MR images.

An Illustrated Scoping Review of the Magnetic Resonance Imaging Characteristics of Canine and Feline Brain Tumors

“…After the exclusion of studies describing experimentally induced brain tum other irrelevant records, de-duplication of records appearing repeatedly in our searches using the different MeSH search phrases, and removal of studies that c < 3 cases, unconfirmed diagnoses, or limited MRI data, we identified 67 articles (F that fulfilled the inclusion criteria, with these studies reporting a total of 1630 cani 59 studies) and 125 feline cases (from 9 studies) with tumors [2,[6][7][8][9][10][11][12][13]25,26, of 62/67 studies were classified using Oxford hierarchal evidentiary criteria [2 (73%) were level 2b retrospective cohort studies [2,6-11,25,26,29,31-33,35-37,40-4 59,63-67,69-72,74,77,78,81-83], 14/62 (23%) were level 4 case series each describ animals [30,38,43,47,49,50,58,61,62,73,75,76,79,80], and 3/62 (4%) were level 3a 'm views containing source data quality heterogeneity [12][13][14]. Five radiomic stud identified [34,[44][45][46]68], with all radiomic studies having QUADAS-2 scores ≤ 6, were considered to provide low-level evidence [28].…”

“…This extra-axial classification scheme refers to lesions arising from the meninges, interior to the calvarium, and exterior to the neural parenchyma [10,[12][13][14] but intentionally excludes extra-axial masses arising in sellar/parasellar or intraventricular locations (Figure 2) for the purposes of refining differential diagnostic considerations. Meningiomas are the most common extra-axial, meningeal-based tumor in both dogs and cats, with other sporadic neoplastic differential diagnostic considerations including histiocytic sarcoma (HS), lymphoma, solitary brain metastases, granular cell tumor (GCT) mesenchymal non-meningothelial tumors (hemangioblastoma), and embryonal tumors (olfactory neuroblastoma) [2,4,9,12,14,61,62].…”

“…Here, we include non-meningothelial mesenchymal tumors (hemangioblastoma, primary intracranial sarcoma), embryonal tumors (neuroblastoma), and granular cell tumors (GCT), predominantly because each of these rare tumor variants may demonstrate MRI features that closely mimic the appearance of meningiomas [2,9,10,14,61,62]. Nonmeningothelial mesenchymal tumors have also presented diagnostic challenges to neuropathologists, with some possibly having been previously classified as vascular hamartomas, undifferentiated sarcoma, or meningeal sarcomas [2,10,84].…”

“…These tumors also appear demarcated, plaque-like lesions involving the cerebral convexities, falx cerebri, or meninges of the skull base. In dogs, GCT may be iso-to hyperintense or hypointense on T2W images, with the majority demonstrating mild hyperintensity on pre-contrast T1W images (Figure 3, Case 5), strong homogenous contrast enhancement, significant mass effect, and perilesional edema [61,62].…”

“…The predominant, non-pituitary origin neoplastic differential diagnoses for sellar and parasellar masses include meningioma (Figure 4, Case 13), lymphoma (Figure 4, Case 15), HS, 3rd ventricular choroid plexus tumors (CPT), cranial nerve sheath tumors, and hematogenous brain metastases, with the MRI features of most of these tumors included elsewhere in this review [2,12,48,55,[57][58][59]63,81]. Other rare tumor types that should be considered for solitary masses in this location include ependymoma, GCT, craniopharyngioma (Figure 4, Case 14), optic nerve pathway or hypothalamic gliomas, and germ cell tumors [61][62][63]70].…”