Contributed by Deepali Jain, MD, DNB1, Subimal Roy, MD, PhD1, Sunita Bhalla, MD1, Veer Singh Mehta, MS, Mch2
1Department of Pathology, Sir Ganga Ram Hospital, New Delhi, India, 2Department of Neurosurgery, Paras Hospitals, Gurgaon, Haryana, India
A26- year- old male presented with difficulty in walking and shakiness on the right side of the body for 8 to 9 months. The patient also complained of diplopia and progressively decreasing sensation of taste on the right side of the tongue. On neurological examination, the patient was conscious and oriented. There was right upper motor neuron facial nerve palsy. The cerebellar signs were positive. The magnetic resonance imaging (MRI) revealed 4.7x4.6x4.3 cm posterior fossa mass lesion in midline and right cerebellar hemisphere. It was hypointense on T1w and heterogeneously hyperintense on T2w and flair images with areas of blooming on gradient images (calcification / hemorrhage). The mass was compressing the 4th ventricle with upstream hydrocephalus. It involved right inferior cerebellar peduncle and medulla with mass effect on brain stem and a focal hyperintense focus in continuity with the right dorsal medulla. On post-contrast images there was significant enhancement of the lesion (Figure 1). The patient underwent an uneventful midline craniotomy with tumor excision by transvermian approach. The patient was referred for radiotherapy and alive at 6 months postoperatively.
Resection of the lesion showed a heterogenous tumor. It was comprised of poorly differentiated spindle cells associated with masses of osteoid, bone and cartilaginous differentiation (Figure 2, 3). Many fragments revealed interlacing bundles of spindle shaped cells with hyperchromatic nuclei. Nuclei showed mild pleomorphism and brisk mitosis (Figure 4). No rosettes were identified. Admixed with spindle cell fascicles, areas of loose fibrillary stroma containing oligodendroglial and astrocytic cells were seen (Figure 5). Reticulin stain showed increased reticulin in the spindle cell areas (Figure 6). Spindly undifferentiated areas were positive with synaptophysin (Figure 7). Focal myogenin, SMA and desmin reactivity was recognized in these areas. Intervening cells in fibrillary background were positive with GFAP (Figure 8). EMA was negative. MIB1 was high (20-25%).