Contributed by Vikram Singh, MD1, Kirti Gupta, MD1, Apinder Preet Singh, MS, M Ch2, Pravin Salunke, MS, M Ch2
Departments of Histopathology1, and Neurosurgery2, Post Graduate Institute of Medical Education and Research, Chandigarh India
A 43-year-old gentleman presented with swelling over scalp for past four months which was initially painless, hard and progressively increasing in size. It became painful in last one month, which was dull aching, intermittent and relieved by medication. There was no history of seizures, weakness, loss of consciousness, trauma, blurring of vision or vomiting. On examination, the vitals were stable with Glasgow coma scale of E4-V5-M6. Bilateral pupils were of normal size with normal reaction. There were no sensory or motor deficits and cerebellar signs were negative. Contrast enhancing MRI showed bone destructive lesion over parietal region. Axial CT showed a lytic lesion of the calvaria in the midline (Fig. 1a). Some expansion of bone with sclerosis was noted. Sagittal and coronal MRI revealed a midline parietal calvarial lesion, indenting the intact underlying dural structures and expanding the overlying galea (Figs. 1b, 1c). With a preoperative diagnosis of midline fronto-parietal calvarial tumor, a midline fronto-parietal craniotomy was performed and near total excision was achieved. Intraoperatively, a firm to hard pinkish tumor was visualized in the calvarium which was adherent to dura and infiltrating through the calvarial bone. Entire tumor with surrounding 1 cm of bony margin was excised. Post-operative period was uneventful.
Histology revealed a focally encapsulated spindle cell tumor with cells arranged in interlacing short fascicles and sheets with variable degree of hyalinization and collagenisation in the background (Figs. 2a, 2b). The tumor cells were fusiform to oval in shape with vesicular chromatin, conspicuous nucleoli and moderate pink cytoplasm (Fig. 2c). Mitotic activity was brisk (2-3/HPF) in areas with cellular pleomorphism (Fig. 2d). The central core of the tumor showed hyalinization (Fig. 2e) with focal necrosis. The tumor was infiltrating the dura and overlying skull bone, however, no parenchymal invasion was identified. On performing immunohistochemistry, the tumor cells showed strong and diffuse positivity for vimentin and smooth muscle actin (SMA) and focally for desmin (Figs. 3a, 3b). These tumor cells are negative for Pan-CK, EMA, Bcl-2 and CD34 (Fig. 3c). Electron microscopic examination revealed intermediate filaments of width corresponding to those of actin filaments. What is your diagnosis?