Introduction There are scant data on renal cell carcinoma (RCC) from relatively younger patients in South America using contemporary classification. Methods Fifty-nine consecutively treated patients with RCC (≤40 years old) were assessed from the National Institute of Neoplastic Diseases in Peru from 2008 to 2020 (34 males; 25 females), age range of 13 to 40 years. Results Most common presenting symptoms were flank pain (n = 40), hematuria (n = 19), and weight loss (n = 12). Associated conditions included 4 patients with proven or presumed tuberous sclerosis and 1 patient with von Hippel Lindau syndrome, all with clear cell RCC. Tumor histopathology was clear cell RCC in 32 of 59 (54%), chromophobe RCC in 6 of 59 (10%), and 5 of 59 (8%) each of papillary RCC and MiT family translocation-associated RCC. Four of 59 (7%) were FH-deficient RCC and 2 of 59 (3%) remained unclassified. The remaining tumors were isolated examples of clear cell papillary renal cell tumor, eosinophilic solid and cystic RCC (ESC RCC), RCC with fibromyomatous stroma, sarcomatoid RCC, and sarcomatoid clear cell RCC. Of the 4 FH-deficient RCCs, none had the classic morphology. The 5 MiT family translocation RCCs had variable morphology. There were 41 tumors without recurrence or metastases, 3 tumors with local recurrence only, 8 tumors with metastases only, and 7 tumors with both local recurrence and metastases. Conclusions The current study demonstrates the importance of special studies in accurately classifying RCC in younger individuals. The distribution of RCC subtypes in younger individuals is similar between 2 representative large institutions of the United States and Peru.

Background: Clear cell sarcoma (CCS) of soft tissue is a rare disease with a high risk of metastasis to regional lymph nodes and distant organs and a poor survival rate. The aim of this study is to determine the rate of lymph node involvement, the effectiveness of treatment, the risk of recurrence and progression after surgery. Methods: We collected data from twenty patients diagnosed with CCS and treated in our institute, between 1998 and 2018. Subsequently, survival rates were determined according to local, regional and distant involvement, as well as the prognostic factors. Results: Twenty patients with CCS were included. The 2-year survival rate was 20%, and the 5-year survival rate was 5%. Patients with CCS with local stage and with tumor size < 5.0 cm were more likely to have a good survival rate. Conclusion: The initial management is crucial for the prognosis of the disease, with surgery being the mainstay of treatment. This study revealed a high rate of lymph node metastasis, so regional lymph node dissection should be done. Finally, the role of chemotherapy and/or radiotherapy for survival is still unclear. Keywords: Sarcoma; clear cell sarcoma; soft tissue tumors

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El tumor miofibroblástico inflamatorio es una neoplasia mesenquimal infrecuente, realizar el diagnóstico clínico así como el patológico por biopsias es un desafío. Presentamos un caso de un paciente pediátrico con tumor miofibroblástico inflamatorio localizado a nivel de las vías biliares. Se realizaron estudios de laboratorio así como imagenológicos en los cuales se planteó un diagnóstico inexacto, del mismo modo cuando se envió la muestra de la lesión para el análisis intraoperatorio a través de técnicas de congelación, el reporte microscópico también fue incorrecto. Sin embargo cuando se realizó la revisión de las láminas tras la inclusión de la lesión y complementando con estudios de inmunohistoquimica, se concluyó que la lesión correspondió a un tumor miofibroblástico inflamatorio.

Sclerosing epithelioid fibrosarcoma (SEF) is a rare fibrosarcoma variant that features rounded carcinoma-like epithelioid cells arranged into compact nests, cords, and single-cell patterns within a highly sclerotic stroma and has a consistent translocation (EWSR1-CREB3L1/2). To our knowledge, there are 110 cases of pure SEF reported, to date, with 15 occurring at intra-abdominal sites. Primary SEF of the kidney is exceptionally rare. We present a case of SEF that arose in the kidney. Histological examination revealed densely hyalinized epithelioid tumor suggestive of SEF. The diffuse immunohistochemical staining of MUC4 by neoplastic cells and the presence of EWSR1 gene rearrangement by fluorescence in situ hybridization analysis confirmed the histological diagnosis.