Chiara Grassani1, Michele Potenzoni1, Nicoletta Uliano1, Anna Maria Pieri1, Daniel Martines1, Sergio Destro Pastizzao1, Roberto Arnaudi1, Antonio Savino1, Andrea Prati1
  • 1 Ospedale di Vaio (Fidenza)


Cystic renal neoplasms constitute a broad and various category of disorder, ranging from benign indolent to aggressive neoplasm. The spectrum of renal cystic lesions includes: multilocular cystic nephroma, multilocular cyst renal cell carcinoma, renal cell carcinoma with cystic change, Wilm's tumor and hydronephrotic kidney. The differential diagnosis is often challenging and the radiologic report is not always sharply diriment.
Muliticystic nephroma (MN) is a rare benign cystic lesion of the kidney, originally described in 1892, since then, about 200 cases were reported in literature. It shows a bimodal distribution with a first peak incidence in 24 months old male children and another one in women over 40 years old. Its etiology is still uncertain.
The non-specific clinical findings and the poor contribution of imaging studies, make the surgical intervention the effective method to exclude a malignant cystic lesions of the kidney.

Materials and Methods

A 32 years old healthy female was admitted to our Operative Unit for evaluation of not specific urinary tract symptoms and intermittent left flank pain, without fever or other systemic symptoms. Personal and familial history were negative for neoplasm, urinary stone or other significant urologic disease. Her physical examination was unremarkable, except for a mild knocking pain at the left flank.
Abdominal ultrasonography (US) revealed a voluminous complex cystic mass at the medium-lower pole of the left kidney.
The computed tomography (CT) showed a 13×15 cm pluriconcamerated cystic mass occupying the medium-lower pole of the kidney. The fluid filled cysts were separated by septations with variable contrast enhancement, mild delayed contrast, occasional periseptal calcifications and hypotropfic arterial vessels. Not solid areas were founded. The well-demarcated mass showed an extensile growth, protruding in the renal sinus and reaching the omolateral iliac fossa, strictly in contact with the left colon. A few lymph nodes with increased volume were described.


A left radical nephrectomy with lombothomic access was performed.
The surgical specimen was sent to the Histopathology Unit.
Macroscopic examination of the surgical specimen revealed a 14x13x9 cm tumor mass. Cut section was constituted of a multilocular cystic lesion composed of numerous not communicating fluid filled cyst of various dimensions, separated by thin to thick fibrous septa.
The microscopic specimen revealed a mixed stromal and epithelial neoplasm with a fibroblastic-myofibroblastic, edematous and hypocellular stroma and few adipocytes. No mesenchimal blastematous or clear cell components were found. The cysts were lined by a variable epithelium from flat to columnar, with also hobnail cells in some areas.
The final diagnosis was of an adult cystic nephroma.


Muliticystic nephroma (MN) is a rare benign, non-familial, cystic lesion of the kidney. It was firstly described in 1892, since then, about 200 cases were reported in literature.
The pathogenesis of MN is controversial and its classification confused. There are numerous theories about its etiology as a developmental defect. Some authors hypothesize that cystic nephroma, like the pleuropolmonary blastoma of the lung, represents a spectrum of abnormal renal organogenesis with risk for malignant transformation, based on study on DICER1 mutations in particular in children. In general, MN is considered to be a segmental form of renal dysplasia related to polycystic disease or alteration of the growth of the ureteric bud. It is also regarded as a neoplasm, occurring at the benign end of the wide spectrum of a continuum. According to the World Health Organization (WHO) classification of renal neoplasm, MN is grouped in the mixed epithelial and stromal tumors (MEST) [bons]
MN has a bimodal age distribution, being reported both in children both in adults. It is more common in infant age between 2 and 4 years. In this group it displays a major incidence in male: 73%. In adult age it is especially seen in 4st-6st decade, affecting predominantly female: M:F=1:8.
Abdominal mass is common onset in children while abdominal flank pain, abdominal discomfort, hematuria and recurrent urinary tract infections are usually findings in adults. Most patients are asymptomatic and tumors discovered incidentally during routine examinations or radiological investigations.
The CT and magnetic resonance imaging findings are suggestive for an encapsulated, multilocular cystic fluid filled mass with variable contrast enhancement of septa.
Being the radiologic report not always sharply diriment, and the clinical data not specific, the differential diagnosis is often challenging, as in the case we presented.
Boggs and Kimmelstiel formulated first diagnostic criteria of a multilocular cyst in 1951 and later modified in 1956 [bogss]. They included: a multilocular mass, cyst lined by epithelium, non communications between cyst or between cyst and the renal pelvis, no normal nephron in the septa, remaining parenchyma essentially normal.
Joshi and Bechwith modified these criteria in 1989. The new terminology emphasized the neoplastic rather than the developmental origin. This new version specified that: the tumor is entirely composed of cysts and septa in a well demarcated mass, septa are the only solid components, the cysts are lined by cuboidal to flattened epithelial cell, or hobnail epithelium, septa contain fibrous tissue, in which well differentiated tubules may be present.
Cytological preoperative study, were performed in order to establish a preoperative diagnosis. Fine needle aspiration cytology with Papanicolau staining of the cystic fluid is now considered not appropriate.


The definitive diagnosis can only be obtained postoperatively being preoperative diagnosis challenging specially in adults. The clinical presentation consists of non-specific symptoms such as abdominal pain, flank pain, hematuria, urinary tract infections, abdominal mass, as the radiologic reports. This creates a difficult differential diagnosis from malignant cystic renal neoplasm, in particular in adults and it has to be considered in the differential diagnosis of malignant renal tumors both in children both in adults
Surgery is the treatment choice to exclude malignant lesions; it includes radical nephrectomy and parenchymal sparing procedures tumorectomy. The choice is based on the characteristic of the neoplasm such as dimensions, vascularization, symptoms and comorbidities. Final diagnosis can be established only at the histopathology examination of the rejected tumor.


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