Rare anaplastic sarcoma of the kidney: A case report

BACKGROUND: Anaplastic sarcoma of the kidney (ASK) is a rare and newly recognized renal neoplasm. The tumor usually is extensive and cystic, characterized by pleomorphic spindle cells with marked atypia and associated with multinucleated cells. To date, only 27 cases have been reported in the literature. The authors present an additional case and summarize the relevant knowledge in the literature. CASE SUMMARY: A 27-year-old previously healthy woman presented with a palpable mass over the abdomen and right flank soreness for one year. After the computed tomography study, the patient underwent right radical nephrectomy obtaining a 1680-g tumor with a size of 18.4 cm × 14.5 cm × 11 cm. The tumor is chiefly composed of anaplastic spindle cells with marked nuclear atypia admixed with multinucleated cells. Immunohistochemical evaluation of tumor cells exhibited diffuse positivity for CD56, p53, and vimentin, and focally positive for desmin. The diagnosis of ASK was established. Unfortunately, a local tumor recurrence followed by a distant metastasis developed within months. The patient died 26 months after the initial surgery. Comparing to the previously 27 cases of ASK, the current case had a relatively worse prognosis, which might be potentially associated with older patient age, larger tumor size, and the lack of en-bloc resection of adjacent organs during the initial radical nephrectomy. CONCLUSION: This case points out the featured pathological findings for diagnosing ASK and suggests more aggressive management for patients with ASK.