Multiparametric Magnetic Resonance Imaging Correlates of Isocitrate Dehydrogenase Mutation in WHO high-Grade Astrocytomas.

Purpose and background: Isocitrate dehydrogenase (IDH) mutation and O-6 methyl guanine methyl transferase (MGMT) methylation are surrogate biomarkers of improved survival in gliomas. This study aims at studying the ability of semantic magnetic resonance imaging (MRI) features to predict the IDH mutation status confirmed by the gold standard molecular tests. Methods: The MRI of 148 patients were reviewed for various imaging parameters based on the Visually AcceSAble Rembrandt Images (VASARI) study. Their IDH status was determined using immunohistochemistry (IHC). Fisher's exact or chi-square tests for univariate and logistic regression for multivariate analysis were used. Results: Parameters such as mild and patchy enhancement, minimal edema, necrosis < 25%, presence of cysts, and less rCBV (relative cerebral blood volume) correlated with IDH mutation. The median age of IDH-mutant and IDH-wild patients were 34 years (IQR: 29−43) and 52 years (IQR: 45−59), respectively. Mild to moderate enhancement was observed in 15/19 IDH-mutant patients (79%), while 99/129 IDH-wildtype (77%) had severe enhancement (p-value <0.001). The volume of edema with respect to tumor volume distinguished IDH-mutants from wild phenotypes (peritumoral edema volume < tumor volume was associated with higher IDH-mutant phenotypes; p-value < 0.025). IDH-mutant patients had a median rCBV value of 1.8 (IQR: 1.4−2.0), while for IDH-wild phenotypes, it was 2.6 (IQR: 1.9−3.5) {p-value = 0.001}. On multivariate analysis, a cut-off of 25% necrosis was able to differentiate IDH-mutant from IDH-wildtype (p-value < 0.001), and a cut-off rCBV of 2.0 could differentiate IDH-mutant from IDH-wild phenotypes (p-value < 0.007). Conclusion: Semantic imaging features could reliably predict the IDH mutation status in high-grade gliomas. Presurgical prediction of IDH mutation status could help the treating oncologist to tailor the adjuvant therapy or use novel IDH inhibitors.

Rhinosporidiosis isolated to the distal clavicle: a rare presentation clinicoradiologically mimicking a bone tumor.

Rhinosporidiosis is a chronic granulomatous disease caused by Rhinosporidium seeberi, which commonly affects young men and predominantly involves the mucous membranes of the nose, nasopharynx and eyes. Involvement of extranasal sites including bone has been reported, but rarely. We present a case of a 32-year-old farmer, who presented with a non-tender, fixed swelling over his right shoulder. Radiography and CT imaging showed an expansile, lytic, destructive lesion involving the lateral end of the right clavicle with soft tissue extension. The clinicoradiological impression was that of a primary bone tumor. Biopsy and wide excision of the lesion revealed features of rhinosporidiosis. There were no mucocutaneous lesions. Involvement of bone without associated mucocutaneous lesions is exceedingly rare in rhinosporidiosis. Involvement of the clavicle, as seen in the present case, has not been reported in the English language-peer reviewed literature, to the best of our knowledge.