Differential Expression and Utilisation of CD34, EMA, PR, and Inhibin in Differentiating Meningioma, Haemangioblastoma, and Solitary Fibrous Tumour: A Cross-sectional Study

Introduction: Mesenchymal tumours of the Central Nervous System (CNS) include meningioma, haemangioblastoma, and Solitary Fibrous Tumour (SFT). Although conventional histopathological examination remains the mainstay in diagnosis, Immunohistochemistry (IHC) plays an important role in CNS tumours, owing to its diagnostic significance and prognostic implications. Aim: To evaluate whether combined use of inhibin, Epithelial Membrane Antigen (EMA,) Progesterone Receptor (PR) and CD34 improves diagnostic accuracy in meningeal and non meningeal mesenchymal tumours of CNS. Materials and Methods: This was a cross-sectional retrospective observational study conducted in the Department of Pathology, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India, October 2022 to December 2022 in which all brain tumour specimens diagnosed as meningeal or non meningeal mesenchymal tumours from January 2022 to August 2022 were included in the present study. Sections were immunostained with an IHC panel of EMA, PR, inhibin, CD34, and Ki67. The immunohistochemical expression of EMA, PR, inhibin, and CD34 was expressed as frequencies and percentages, along with sensitivity and diagnostic accuracy evaluation. Ki67 was assessed in the hotspots and expressed as a percentage. The data were presented as frequencies and percentages. Results: A total of 60 patients were included, with an age range from 12 to 73 years and a mean age of 48.2 years. Female predominance, constituted 40 (67.5%) of the study population. Out of the total cases, 49 (81.7%), 9 (15%), and 2 (3.3%) cases were of meningioma, haemangioblastoma, and SFTs, respectively. Among the 49 cases of meningioma, the majority 47 (96%) showed diffuse and strong staining for EMA with a cytoplasmic staining pattern±membranous accentuation. PR was expressed in 45 (92%) of the meningiomas. Inhibin was diffusely expressed in stromal cells of haemangioblastoma 9 (100%). A characteristic cytoplasmic positivity of CD34 was observed in both cases 2 (100%) of SFT. The Ki67 index of anaplastic and atypical meningiomas was 15%, while all other tumours had a very low proliferation index of 2%. Conclusion: The IHC panel comprising CD34, EMA, and inhibin was useful in the differential diagnosis of both meningeal and non meningeal mesenchymal tumours in the CNS, even in cases with overlapping histomorphological features. Inhibin had a very high sensitivity and diagnostic accuracy for the diagnosis of haemangioblastomas. EMA and PR also had fairly good sensitivity and diagnostic accuracy for the diagnosis of meningiomas. CD34 had good sensitivity but very poor diagnostic accuracy for the diagnosis of SFT.