Cellular congenital mesoblastic nephroma in a newborn

Typical nephroblastoma (Wilms'tumor) is uncommon within the first 6 months of life. Renal tumors most commonly found in this age constitute of two groups which have a better and worse prognosis, respectively, than typical nephroblastomas. The group of tumors with a better prognosis encompasses congenital mesoblastic nephroma (CMN), fetal rhabdomyomatous nephroblastoma and cystic, partially differentiated nephroblastoma. The group of tumors with a worse prognosis consists of rhabdoid tumor of the kidney and bone metastasizing renal tumor (clear cell sarcoma) of childhood. Adequate therapy for these two neoplasms has as yet to be developed. Among the low-grade malignant tumors congenital mesoblastic nephroma can be successfully treated with simple nephrectomy. There, are however, variants of CMN which may differ in clinical behavior from the typical form of CMN. These variants include the cellular CMN2 and, possibly, the malignant mesenchymal nephroma of infancy. A case of cellular congenital mesoblastic nephroma is presented here. Its clinical and pathologic features are discussed.     

Aspiration cytology of mesoblastic nephroma in an adult: diagnostic dilemma

A case of adult mesoblastic nephroma (MN) was erroneously interpreted as a benign mesenchymal tumor on fine-needle aspiration (FNA) cytology. MN is a rare tumor in infants and is extremely uncommon in adults. A 50-yr-old female presented with a renal lump with the clinicoradiological possibility of renal-cell carcinoma. Giemsa-stained smears were highly cellular and showed cohesive interlacing fragments of spindle cells embedded in abundant pink fibrillary stromal matrix. Epithelial component was seen in the form of tubules. Pleomorphism, mitosis, and necrosis were absent. Cytologic features in both adult and infantile MN are similar, but in an adult can be mistaken for benign or malignant mesenchymal tumor and the sarcomatoid variant of renal-cell carcinoma. FNA in such a rare yet cytomorphologically characteristic lesion can be helpful in guiding the management. Awareness on the part of both the clinician and the cytopathologist is necessary to resolve the diagnostic dilemma.     

Two chromosomally different cell populations in a partly cellular congenital mesoblastic nephroma

The conventional fibromatous and cellular areas of a congenital mesoblastic nephroma were studied using electron microscopy, and in vitro and cytogenetic methods. In light- and electron-microscopic studies, as well as in cell cultures, mature and immature mesenchymal cell types that corresponded to the fibromatous and cellular areas of the tumor were found. The conventional fibromatous portion of the tumor showed a normal chromosomal pattern, while the cellular, pleomorphic tumor area was characterized by an aneuploid clone with 54 chromosomes. The value of cytogenetic analysis of congenital mesenchymal renal tumors as a possible diagnostic tool in histologically questionable cases is discussed.     

Mesoblastic nephroma

Three cases of the "cellular" variant of mesoblastic nephroma are reported. A feature of one of them was prolonged (7.5 months) spontaneous development of the tumor which presented a peculiar morphologic appearance. Diagnostic differentiation of mesoblastic nephroma from Wilm's tumor and sarcomas is discussed. Results of an electron-microscopic study of one of the tumors are given.     

Lessons learned from the developmental origins of childhood renal cancer

Despite the rarity of renal tumors in children, many different types of malignant and nonmalignant renal neoplasms have been described. Therefore, the correct diagnosis and clinical management of these patients can represent a challenge. Here we provide a comprehensive review of the commonly diagnosed pediatric renal malignancies, including nephroblastoma (commonly known as Wilms tumor), clear cell sarcoma of the kidney, rhabdoid tumor of the kidney, several subtypes of renal cell tumors (often collectively termed renal cell carcinoma), and congenital mesoblastic nephroma. The epidemiology, pathology, treatments, underlying genetic and molecular mechanisms, and proposed developmental origins are discussed in detail, highlighting differential features and potential improved therapeutic strategies for affected individuals.     

Atypical congenital mesoblastic nephroma. Report of a case with karyotypic and flow cytometric analysis

Atypical congenital mesoblastic nephroma is a rare infantile renal tumor that may behave aggressively in older infants. A case of atypical congenital mesoblastic nephroma occurring in an 8-month-old hispanic male was analyzed by routine histopathologic, cytogenetic, and retrospective flow cytometric analysis for DNA ploidy. Light microscopy revealed marked hypercellularity. The karyotype was abnormal, with the following configuration: 45,XY,-1,-3,-9,-9,-15,-17,-21,+del(1)(q21q25),+der(3), t(3;9;15)(q23;p22;q11),+der(9),t(3;9;15) (q23;p22;q11),+der(9),t(9;?) (p?22;?),+r21, + mar. Retrospective DNA ploidy analysis revealed a DNA index of 1.0. The significance of karyotypic changes occurring in mesenchymal renal tumors of this type is currently unknown. Cytogenetic analysis might be of prognostic value in these potentially aggressive tumors.     

Benign tumors and tumor-like lesions of the adult kidney. Part II: Benign mesenchymal and mixed neoplasms, and tumor-like lesions

In this review article the benign tumors and tumor-like lesions of the adult kidney are discussed. The incidence of benign renal tumors is low, especially when compared to renal cell carcinomas, as most are detected incidentally or at autopsy. Some of these tumors, as their names imply, are unique to the kidney, e.g., renal adenoma, metanephric adenoma, renal oncocytoma, nephrogenic adenofibroma, mesoblastic nephroma, capsuloma, juxtaglomerular cell tumor, renomedullary interstitial cell tumor (medullary fibroma), cystic nephroma, cystic partially differentiated nephroblastoma, and cystic hamartoma of the renal pelvis, while others, such as angiomyolipoma, leiomyoma, hemangioma, lipoma, etc., are not unique to the kidney and show similar morphologic features in the other sites they affect. Of the tumor-like lesions, xanthogranulomatous pyelonephritis, malakoplakia, and renal cysts are the most common. The other entities, such as fibroepithelial polyp, are rare, most having been the topic of case reports. In Part I of this paper the benign epithelial tumors of the kidney were previously discussed. This paper (Part II) is devoted to the benign mesenchymal tumors, mixed mesenchymal and epithelial tumors, and the tumor-like lesions.     

Cytological diagnosis of mesoblastic nephroma: A report of three cases with summary of prior published cases

Congenital mesoblastic nephroma (CMN) is a rare pediatric renal neoplasm, occurring most commonly in the first few months of life, with a favourable clinical outcome. Accurate pre‐operative cytological diagnosis of this entity is important as pre‐operative chemotherapy is not recommended and surgery is the treatment of choice. Cytodiagnosis of this rare tumor is discussed in only a few case reports. Here two cases of CMN and one case of cellular congenital mesoblastic nephroma (CCMN) diagnosed on FNAC along with their morphological differential diagnoses has been reported. They also take this opportunity to compare the cytological features of CMN with cellular CMN. Diagn. Cytopathol. 2016;44:823–827. © 2016 Wiley Periodicals, Inc.     

Atypical mesoblastic nephroma. Pathologic characterization of a potentially aggressive variant of conventional congenital mesoblastic nephroma

A case of an aggressive variant of conventional congenital mesoblastic nephroma (CMN) occurred in a 10-month-old male infant. The tumor proved to be fatal, with two abdominal recurrences, but no metastases were found. Of the various terms used to designate the tumor, atypical mesoblastic nephroma (AMN) is preferred. We reviewed 17 previously reported cases to attempt pathologic characterization of AMN. The features that distinguish AMN from CMN are as follows: (1) atypical gross features consisting of one or more of the following: fleshy areas, foci of hemorrhage, necrosis, involvement of adjacent structures other than connective tissue; and (2) high cellularity and mitotic index. Aggressive behavior was noted at surgery or on follow-up in seven of the 18 cases. It was characterized by one or more of the following: (1) invasion of adjacent structures, such as adrenal gland, spleen, colon, and diaphragm (three cases); (2) one or more recurrences (four cases); and (3) metastasis (two cases). Atypical mesoblastic nephroma should be recognized as a potentially aggressive lesion separate from CMN.     

Classical and cellular (atypical) congenital mesoblastic nephroma: a clinicopathologic, ultrastructural, immunohistochemical, and flow cytometric study

Sixteen cases of congenital mesoblastic nephroma (CMN) were studied. The tumors showed variable patterns of growth, degrees of cellularity, and mitotic activity. Six tumors had the classical pattern of CMN, seven were of the cellular or atypical variant and three showed combined features. The mean ages at presentation were 16 days, 5.3 months, and 2.3 months, respectively. Average size and weight were 5.1 cm and 94 g for classical CMN, 9.1 cm and 620 g for cellular CMN and 10.5 cm and 150 g for combined tumors. Cyst formation, hemorrhage and necrosis were confined to cellular CMNs and to cellular areas of combined CMNs. Mitotic activity ranged from 0 to 1/10 high-power fields (HPFs) in classical tumors to 25 to 30/10 HPFs in cellular tumors. Clear cell sarcoma-like areas were observed in three neoplasms. In ten cases there was invasion of perirenal fat; in one case each, invasion of the psoas muscle, renal vein wall, and renal vein lumen was observed. Ultrastructural and immunohistochemical studies showed features consistent with myofibroblastic differentiation. Flow cytometric analysis revealed euploidy in one classic CMN, one cellular CMN and in classic areas of a combined CMN; cellular areas of the latter tumor were aneuploid. All patients with follow-up were alive without evidence of disease after a mean period of 5 years following nephrectomy alone. No correlation was observed between the pathologic features assessed and the biologic behavior of these neoplasms.     

Multicystic congenital mesoblastic nephroma

This report describes an unusual example of congenital mesoblastic nephroma cellular variant that presented in a 1-week-old neonate as a multicystic tumor of the kidney. Extensive pseudocystic cavitation resulted from progressive accumulation of ground substance in a loosely myxoid tissue composed of stellate- and spindle-shaped cells that compressed and infiltrated renal tissue. The cells of the tumor were positive for vimentin and smooth muscle actin. The patient is alive and well 16 years after surgery. Differential diagnosis from segmental cystic dysplasia, cystic intralobar nephrogenic rest, cystic nephroma, cystic partially differentiated nephroblastoma, cystic nephroblastoma, and cystic clear cell sarcoma of the kidney, all of which may present at this age, is discussed.     

Adult variant of congenital mesoblastic nephroma

Congenital mesoblastic nephroma is a relatively rare tumor predominantly of childhood. Occurrence in adults is exceedingly rare and, to my knowledge, only two cases have been reported to date. This article pertains to a mesoblastic nephroma in a 41-year-old woman. The tumor was composed mainly of compact fibrocollagenous elements interspersed with areas containing immature tubules and occasionally glomeruloid structures. There was no evidence of capsular or renal invasion or cytological malignant features. It has been postulated that this neoplasm may represent a form of mature Wilms' tumor with a benign clinical course.     

Congenital mesoblastic nephroma - a semimalignant fibroleiomyomatous kidney tumor of the newborn (author's transl)]

The congenital mesoblastic nephroma is a distinct tumor entity, which should be clearly distinguished from Wilmus-tumor. The pure mesenchymal tumor is usually present at birth and palpated as a mass in the kidney. Macroscopically the tumor reveals a striking resemblance with an uterine fibroid. Histologically the tumor tissue ist characterized by 1. interlacing bundels of spindle cells with uniform cell nuclei and regular mitotic figures, 2. collagen fibres between the tumor cells, 3. an angiomatous marginal zone, no tumor capsule, 4. hematopoetic foci and dysplastic glomeruli and tubuli in areas where normal kidney parenchyma mixes with tumor tissue, 5. small myxomatous areas within in the tumor, 6. no invasion of blood vessels or pelvis.Prognosis of the congenital mesoblastic nephroma is much better than in Wilms-tumor. Metastases have not been described so far. If, however, the tumor tissue is incompletly removed during operation, the neoplasm may recur and prove fatal. Ultrastructural and DNA cytophotometric studies suggests a low grade malignancy rather than a truely benign behaviour of this tumor.     

Cellular mesoblastic nephroma in an infant: Report of the cytologic diagnosis of a rare paediatric renal tumor

Congenital mesoblastic nephroma is a rare pediatric tumor with a favorable clinical outcome. Cytological features of this uncommon tumor and diagnostic difficulties with other commoner pediatric renal neoplasms have been inadequately discussed in the available literature. We describe the case of a 1‐year‐old girl who presented with a right renal mass. Fine‐needle aspiration smears consisted of a few cellular clusters of spindle cells with mitotic activity and mild nuclear pleomorphism. No blastema was identified. A cytologic impression of mesoblastic nephroma was rendered, which was confirmed on histopathological examination of the right nephrectomy specimen as a cellular mesoblastic nephroma. Cytologic diagnosis of mesoblastic nephroma has important prognostic and therapeutic implications. The cytopathologist should carefully evaluate smears from such patients and attempt to differentiate mesoblastic nephroma from Wilms' tumor and clear cell sarcoma. Diagn. Cytopathol. 2009. © 2009 Wiley‐Liss, Inc.     

Nephrogenic adenofibroma in a young child

Nephrogenic adenofibroma is a benign renal tumor in children and young adults described by Hennigar and Beckwith in 1992. Seven cases have been described, and we report the first case in an 11-month-old child, in good health, revealed by a macroscopic hematuria. Nephrogenic adenofibroma is an unusual tumor, which was difficult to distinguish from nephroblastoma and mesoblastic nephroma. Beckwith makes a distinction between this principal differential diagnosis in child renal tumors based upon morphologic and immunohistochemical patterns. In our observation, the diagnosis remained difficult and needed several reviews of our case. Beckwith proposed the final diagnosis: nephrogenic adenofibroma with stromal predominance. The prognosis is excellent and no treatment is indicated. A FISH analysis of the tumor cells found a trisomy 11. Trisomy 11 has been reported in mesoblastic nephroma as the most frequent chromosomal abnormality. This finding in tumor cells provides an argument for excluding the diagnosis of nephroblastoma but can not clarify the difference between nephrogenic adenofibroma and mesoblastic nephroma.