Secondary polycythemia is a paraneoplastic syndrome observed in tumors with excessive erythropoietin (EPO) production. Renal cell carcinoma (RCC) and cerebellar hemangioblastoma are the 2 most well-known tumors to induce secondary polycythemia. Hemangioblastomas occurring in the kidney are rare. In this work we present a case of renal hemangioblastoma that caused erythrocytosis in a 19-year-old man. We demonstrated intratumoural EPO production by immunohistochemistry, and conducted whole-exome sequencing to evaluate possible genetic alterations that reported to induce tumor-related polycythemia. In spite of an indolent clinical behavior, renal hemangioblastoma is difficult to differentiate from RCC not only clinically, but also histopathologically. Given that RCC is the most well-known renal tumor to induce erythrocytosis, the uncommon manifestation of polycythemia in renal hemangioblastoma, as shown in our case, can cause further diagnostic challenges. Renal hemangioblastoma should be listed in the differential diagnoses of renal tumors presenting with erythrocytosis, apart from the most common RCC.

In the central nervous system, the presence of pigment in astrocytic tumors is rare.Only nine cases were reported in the English literature: one ganglioglioma, one pilocytic astrocytoma, and seven cases of pleomorphic xanthoastrocytoma (PXA).Though squash cytology is a common and useful tool for intraoperative diagnosis during brain tumor surgeries, the cytologic findings of pigmented PXA have not been recorded previously. We present a 32-year-old woman with a mass in her medial right temporal lobe. Intraoperative squash cytology examination demonstrated pleomorphic tumor cells containing cytoplasmic pigment granules. The subsequent tissue section and additional workup revealed a PXA with melanosomal melanin pigment deposits. While conventional PXA has to be differentiated from high-grade tumors such as glioblastoma, in the pigmented variant the presence of pigment can cause further diagnostic confusion with other pigmented tumors, in particular melanoma. It should be added into the differential diagnoses when a brain tumor smear shows nuclear pleomorphism and intracytoplasmic pigment particles.