Standardization of canine meningioma grading: Validation of new guidelines for reproducible histopathologic criteria

Abstract

Canine meningiomas are currently graded using the human grading system. Recently published guidelines have adapted the human grading system for use in dogs. The goal of this study was to validate the new guidelines for canine meningiomas. To evaluate the inter‐observer agreement, 5 veterinary surgical pathologists graded 158 canine meningiomas following the human grading system alone or with the new guidelines. The inter‐observer agreement for histologic grade and each of the grading criteria (mitotic grade, invasion, spontaneous necrosis, macronucleoli, small cells, hypercellularity, pattern loss and anaplasia) was evaluated using the Fleiss kappa index. The diagnostic accuracy (sensitivity and specificity) was assessed by comparing the diagnoses obtained with the 2 grading systems with a consensus grade (considered the reference classification). The consensus histologic grade was obtained by agreement between 4 experienced veterinary neuropathologists following the guidelines. Compared with the human grading alone, the canine‐specific guidelines increased the inter‐observer agreement for: histologic grade (κ = 0.52); invasion (κ = 0.67); necrosis (κ = 0.62); small cells (κ = 0.36); pattern loss (κ = 0.49) and anaplasia (κ = 0.55). Mitotic grade agreement remained substantial (κ = 0.63). The guidelines improved the sensitivity in identifying grade 1 (95.6%) and the specificity in identifying grade 2 (96.2%) meningiomas. In conclusion, the new grading guidelines for canine meningiomas are associated with an overall improvement in the inter‐observer agreement and higher diagnostic accuracy in diagnosing grade 1 and grade 2 meningiomas.

Cytotoxicity on low-grade canine meningioma with the use of somatostatin analog (octreotide): An in vitro study

“…For each tumor, the remaining half was utilized to establish cell cultures according to previously published protocol. 9 Briefly, after washing the tissue in Dulbecco’s phosphate-buffered saline (PBS; DPBS), without Ca 2 + and Mg, 2 + containing 100 U/mL of penicillin, 100 mg/mL of streptomycin and 250 mg/mL of amphotericin B (Sigma-Aldrich), blood clots and blood vessels were removed. Tumor samples were then dissected to obtain small pieces (1–3 mm) submitted to enzymatic digestion with 2 mg/mL trypsin for 10 minutes at 37°C and with 1.5 mg/mL of collagenase type IA (Sigma-Aldrich) at 37°C for addition 2 hours.…”

“…According to the histological criteria derived from the WHO human classification, recently several veterinary neuropathologists reached a consensus on meningioma grades among dogs so that canine grades I, II, and III meningiomas account for 51.6%, 41.1%, and 7.3% of cases, respectively. 1 , 2 In humans, WHO grade I tumors are significantly more prevalent, accounting for 80.1% of all meningiomas, 3 followed by grade II and finally by grade III meningioma. For this tumor, surgery remains the treatment of choice 4 , 5 either alone or in combination with radiotherapy.…”