Clear cell sarcoma, cellular mesoblastic nephroma and metanephric adenoma: cytological features and differential diagnosis with Wilms tumour

Abstract

Wilms' Tumour (WT) is the most common kidney tumour in childhood, this fact and the embryonic complexity of WT create, whenever one of its three classical components predominates in cytologic smears, difficulties in the differential diagnoses with other less common entities. In the present study, we review the cytological and immunohistochemical characteristics of three children renal tumours, a Clear Cell Sarcoma of the Kidney (CCSK-case1), a Cellular Mesoblastic Nephroma (CMN-case2) and a Metanephric Adenoma (MA-case3) and compare them, for differential diagnostic purposes, with smears of blastematous, mesenchymal and epithelial predominant WTs, previously diagnosed in our Department. In all cases a mass was detected in the abdomen (2 and 8 year old children-cases 1 and 3, respectively), and pre-birth in case 2 (the tumour was detected during pregnancy). Fine needle biopsy was performed followed by routine cytologic examination. The presence of moderate amount of blue pale cytoplasm in neoplastic cells (case1), the presence of tightly cohesive, bland, spindle tumour cells (case2) and the identification of small, well differentiated epithelial tubules with psammoma bodies in case 3, were the main morphologic characteristics that we think represent the most important elements for distinguishing our cases from a WT. Immunoreactivity was only helpful in case 1 as we found a characteristic dot-like pattern positivity for vimentin, in the absence of immunoreactivity for the other markers that are usually positive in WT. Summing up, these three cases demonstrate that cytopathologists should be aware of the occurrence of uncommon renal neoplasms in childhood and should be acquainted with their characteristics, in order to avoid false diagnoses.

Conservative treatment of metanephric adenoma. A case report and review of the literature

“…Mean age at diagnosis is between 40 and 50 years old [3,4], and there is a male:female ratio of about 1/2 [3]. Over 100 cases have been reported in the literature, of which 20 pertain to children [3,4,6,7,9e17].…”

“…Both show positive staining for WT1 [26]. Therefore, it is important to look for the following differences between the two tumors: the age at diagnosis (far earlier for WT with a mean age of 3 years old, 98% of tumors occurring before the age of 7 years) [27], the presence or not of a capsule (absent in MA), the mitotic activity (intense in WT, relating to the presence of nucleoli and elongated nuclei), as well as with regard to certain immunohistochemical features, including CD56 staining (positive in WT for most authors and negative in MA, except for one publication [4]). In both tumors, stains for cytokeratin 7, EMA and desmin may be negative, while stains for pankeratin AE1/AE3 may be positive.…”

“…There is no blastematous component [2]. A histogenetic link exists with nephroblastoma or Wilms tumor (WT) [3], and differential diagnosis between MA and renal cell carcinoma (RCC) in its papillary form can be difficult [4,5]. Rigorous analysis of pathological criteria is required as these three tumors require different treatments.…”

Nefroma mesoblástico congênito subtipo celular: relato de caso

“…8 However, when fusiform cells predominate in a child's kidney, the differential diagnosis must include WT, clear-cell type RCC (fusiform cell pattern) and CMN, in addition to other entities that are less common in children. 2 The CMN must be treated with radical nephrectomy to reduce the risks of local recurrence. This treatment alone is usually enough, as the tumor has low malignancy potential.…”

“…1 This fact makes this diagnosis the most probable one when an abdominal mass is detected in a child's kidney, very often leading to the treatment directed at WT, even without pathological confirmation. 2 Renal neoplasms in children younger than 6 months are less common. In this group, the congenital mesoblastic nephroma (CMN) is the most frequent one, 1 with 90% of the tumors being diagnosed within the first year of life and, virtually, never occurring after three years of age.…”