Contributed by Balan Louis Gaspar, MD1, Kirti Gupta, MD1, Apinder Preet Singh, MS, M Ch2, Pravin Salunke, MS, M Ch2
Departments of Histopathology 1 and Neurosurgery 2, Postgraduate Institute of Medical Education and Research, Chandigarh. India
A 39-year-old gentleman presented a single episode of hematuria and right flank pain of one month duration. Ultrasonography (USG) and CT of abdomen revealed a 7x5x5 cm right renal mass suggestive of renal cell carcinoma (RCC). While being investigated, he developed worsening headache and visual blurring. Positron emission tomography (PET) scan, CT (Figs. 1a, 1b) and post contrast MRI revealed a hyper-intense lesion in the right cerebellar hemisphere pushing the vermis to left and anteriorly (Figs. 1c, 1d). In view of raised intracranial pressure, he underwent gross total excision of the cerebellar lesion prior to nephrectomy.
Microscopic evaluation revealed a tumor in nests and sheets with large round to oval cells with voluminous cytoplasm and well defined borders. The nuclei were round with fine chromatin, conspicuous nucleoli and wrinkled, prominent membrane giving the characteristic 'rasinoid' appearance. Perinuclear halos with a translucent zone around the nuclei were appreciated in many cells (Figs. 1e, 1f, 1g). Mitotic figures were rare. Hale's colloidal iron stain revealed coarse bluish granules within the cytoplasm of tumor cells (Fig. 1h). There was no evidence of necrosis, sarcomatoid change or rhabdoid differentiation. The tumor cells revealed membranous positivity for CK7, CD117 and nuclear positivity for PAX8 (Figs. 1i, 1j, 1k). The native cerebellar tissue did not reveal any significant changes. What is your diagnosis?