Complete spontaneous regression of a primary renal cell carcinoma. Report of a pathological proven case and review of the literature.

Regression of primary renal cell carcinoma (RCC) is a rare phenomenon and for several reasons many of the reported cases have been questioned. We present a case that can be considered a true spontaneous and complete regression of a primary RCC. A 79-year-old female underwent nephrectomy because a renal tumor. At the time of surgery image studies showed a small para-aortic lymph node. The tumor measured 3cm and was analyzed completely. Histology showed a fibro-inflammatory lesion with necrosis, foamy macrophages and inflammatory cells. No neoplastic cells were observed and the lesion was interpreted as a localized type of xanthogranulomatous pyelonephritis. One year later a CT control scan, showed that the para-aortic lymph node had increased in size to 4cm. Fine needle aspiration revealed features of clear RCC. Metastatic dissemination was limited so surgical removal of the para-aortic lymph node was performed and the cytologic diagnosis confirmed.

Plasmablastic lymphoma phenotype is determined by genetic alterations in MYC and PRDM1.

Plasmablastic lymphoma is an uncommon aggressive non-Hodgkin B-cell lymphoma type defined as a high-grade large B-cell neoplasm with plasma cell phenotype. Genetic alterations in MYC have been found in a proportion (~60%) of plasmablastic lymphoma cases and lead to MYC-protein overexpression. Here, we performed a genetic and expression profile of 36 plasmablastic lymphoma cases and demonstrate that MYC overexpression is not restricted to MYC-translocated (46%) or MYC-amplified cases (11%). Furthermore, we demonstrate that recurrent somatic mutations in PRDM1 are found in 50% of plasmablastic lymphoma cases (8 of 16 cases evaluated). These mutations target critical functional domains (PR motif, proline rich domain, acidic region, and DNA-binding Zn-finger domain) involved in the regulation of different targets such as MYC. Furthermore, these mutations are found frequently in association with MYC translocations (5 out of 9, 56% of cases with MYC translocations were PRDM1-mutated), but not restricted to those cases, and lead to expression of an impaired PRDM1/Blimp1α protein. Our data suggest that PRDM1 mutations in plasmablastic lymphoma do not impair terminal B-cell differentiation, but contribute to the oncogenicity of MYC, usually disregulated by MYC translocation or MYC amplification. In conclusion, aberrant coexpression of MYC and PRDM1/Blimp1α owing to genetic changes is responsible for the phenotype of plasmablastic lymphoma cases.