Brasil

Introduction : MCRCC is a rare entity recently separated from other variants of renal tumors. It represents less than 1% of all renal tumors and 3 -12% of RCCs. There were about 160 cases reported until 2002.
Diagnostic criteria for MCRCC (WHO 2004) are: a neoplasm with an intrinsically cystic growth pattern, and no, or at most little, malignant potential; the expansive mass is surrounded by a fibrous wall; the interior is composed entirely of cysts and septa, with no expansive solid nodules of clear cells. The septa contain aggregates of epithelial cells with clear cytoplasm. As diagnostic criteria there should not be grossly visible solid nodules expanding the septa, and this distinguishes MCRCC from conventional clear-cell RCC with cystic change.
Material and methods : We report on 23 cases of MCRCC found through a multinational and multi-institutional search in a retrospective study of 5 years, with the purpose to better define the clinical-pathologic features of this uncommon entity.
Results : Analysis of our material allowed confirming several data of the literature. All cases were unilateral, with no side predominance. All patients were alive with no evidence of disease at a mean follow-up of 63 months (6 months-16 years). Almost 70% (16) of the patients were male; mean age was 52.5 years (30-68 years); 56.5% of the patients were less than 50 years-old; 4 cases (l7,4%) were found incidentally; mean tumor size was 4.4 cm (1 to 8 cm); all tumors were Stage I (95.7% pT1, 4.3% pT2)(TNM 2002); nuclear grade was 100% low (56.5% Fuhrman 1, 43.5% Fuhrman 2). The reported cases represent 3%, 7.3%, and 1.4% of all RCC seen during the same period of time at our institutions in Brazil, Spain and Japan, respectively.
Conclusions : Our data and information from the literature suggest that MCRCC is a variant of clear cell RCC with very low potential, if any, for recurrence or metastasis and a 5-year disease-specific survival rate of 100%, and surgery is curative. It is our believe that the lesion should be renamed as to indicate the benign nature of this tumor. Renal Cell Cystadenoma would be an appropriate one.

RCC, multilocular clear cell RCC or multicystic clear cell carcinoma, is a rare entity of which nosology, true incidence and a biologic behavior are yet not well known.
It approximately accounts for less than 1% of all renal tumors(1) and 3 -12% of the RCCs(2,3). In 67% of the cases(2,4) the tumor commonly is incidentally found during the evaluation of an unrelated disease or in a general health checkup. Up to year 2002 there were approximately 160 cases reported.
While some authors found no differences in sex distribution(5) other presented male preponderance (96%)(3,6-8), as opposed to 64% in the patients with other types of RCC(9-11).
Age of the patients ranged from 33 to 68 years (mean, 46) (5,6,8,12), notably younger than the usual conventional RCC. All reported tumors were unilateral.
MCRCC has been considered a distinct subtype of cystic RCC, with characteristic gross macroscopic features(5,6,8). It shows typical multilocular cystic appearance, with well-defined multilocular cystic masses filled with gelatinous and / or hemorrhagic fluid. A variegated, yellowish, solid component, characteristic of clear cell carcinoma, is limited to small areas comprising less than 10-25% of the entire lesion(2,5,8). The lesion is variably sized. The mean tumor size varies in the reported series: 3.4 cm, 5.4 cm (range 2 to 9) and 5.8 cm (the greatest diameter ranged from 3 to 12 cm) (2,4,5).
At histopathology(1,5,,6,8), the cysts are lined by a cuboidal or flattened epithelium. However, laminar growth of renal cell carcinoma of the clear cell type is present in some areas in the septa. They are few residual tumor cells found in the irregular, thick, fibrous, hyalinized septa. Nuclear grade (mean tumor grade 1.1) (2-4,8) and pathological stage were usually lower in those with MCRCC that in those with RCC.
In 1998, Eble et al. (13) suggested a diagnostic criteria for MCRCC that was endorsee endorsed by WHO Consensus Classification 2003/2004. It is that MCRCC is a neoplasm with an intrinsically cystic growth pattern, and no, or at most little, malignant potential, composed by: 1- an expansile mass surrounded by a fibrous wall; 2- the interior of the tumor is composed entirely of cysts and septa, with no expansile solid nodule; and 3- the septa contain aggregates of epithelial cells with clear cytoplasm. The pathologic criteria that there should be no grossly visible expansile solid nodule expanding the septa, is easier to apply and more clearly distinguishes MCRCC from conventional clear-cell RCC with extensive cystic change.
So, when renal cell carcinoma is present in only a part of the multilocular cystic renal mass, it should be diagnosed as MCRCC.
Differential diagnosis of MCRCC(7,13-15) in an adult includes multicystic kidney, segmental cystic disease, cystic nephroma, and cystic necrosis in RCC (pseudocystic necrotic carcinoma). Theoretically, in children, MCRCC may prove to be grossly indistinguishable from cystic nephroma, Wilms tumor with cyst formation due to hemorrhage and necrosis, cystic clear cell sarcoma, cystic partially differentiated nephroblastoma, cystic renal cell carcinoma, multicystic renal dysplasia and segmental multicystic dysplasia in a duplicated renal collecting system. However, MCRCC has not been recognized at this age group.
Although this tumor is considered to be a variant of clear cell RCC, it has a very low potential, if any, for recurrence or metastasis and the 5-year disease-specific survival rate is 100%.
The prognosis for patients with MCRCC is better than that for patients with solid tumors like conventional RCC. Maybe MCRCC represents a distinct subtype of RCC that can be completely cured by surgery(2-6,8,16,17).
Present report describes the findings in a multinational effort for collect cases MCRCC and better define its peculiar features.

We report on 23 cases of MCRCC found through a multinational and multi-institutional search in a retrospective study of 5 years. The files of 651 renal tumors were searched for cases coded with the diagnosis of MCRCC, recording sex, age and follow-up of the patients, and side, size, and histopathologic features of the tumor.

The results are presented in Table 1. Almost 70% (16) of the patients were male (Graphic_1). Mean age was 52.5 years (30-68 years) (Graphic_2); 56.5% of the patients were less than 50 years-old. All patients were alive with no evidence of disease at a mean follow-up of 63 months (6 months-16 years). Four cases (l7.4%) were found incidentally. All cases were unilateral, with no side predominance (Graphic_3). Mean tumor size was 4.4 cm (1 to 8 cm) (Graphic_4). All tumors were Stage I-II (95.7% pT1, 4.3% pT2) (TNM 2002) (Graphic_5); nuclear grade was low in all (56.5% Fuhrman 1, 43.5% Fuhrman 2) (Graphic_6). The cases herein reported represent 3%, 7.3%, and 1.4% of all RCC seen during the same period of time at our institutions in Brazil, Spain and Japan, respectively (Graphic_7).
Figure_1 shows the CT scan of a case of MCRCC. Grossly MCRCC (Figure_2-5) appeared as unilateral superficial tumors with multilocular cystic appearance. The microscopic features of MCRCC are depicted in Figures 6 to 14.

Table 1: Multilocular Cystic Renal Cell Carcinoma (MCRCC): Report of 23 Cases
Number Case	Sex	Age (years old)	Renal Side	Tumor Size (greatest dimension)	Furhman Grade (F)	pTNM Pathological Classification 2002	Stage Group
P360-98 Brasil	Female	42	Right kidney	2.0 cm	F1	pT1aN0MXG1	Stage I
P1506-02 Brasil	Male	52	Right kidney	2.4 cm	F2	pT1aN0MXG2	Stage I
P1541-03 Brazil	Male	46	Left kidney	5.5 cm	F2	pT1bN0MXG2	Stage I
1987 SM 2377 Japan	Female	50	Right kidney	7.0 cm	F1	pT1bNXMXG1	Stage I
1991 SM 555 Japan	Male	42	Left kidney	4.5 cm	F1	pT1bNXMXG1	Stage I
1995 SM 225 Japan	Male	66	Left kidney	2.8 cm	F1>>2	pT1aNXMXG1>>G2	Stage I
1996 SM 1689 Japan	Male	64	Left kidney	4.0 cm	F1	pT1aNXMXG1	Stage I
2000 SM 985 Japan	Male	50	Right kidney	1.5 cm	F1	pT1aNXMXG1	Stage I
12019-b99 Spain	Male	41	Left kidney	4.0 cm	F1	pT1aNXMXG1	Stage I
16834-b98 Spain	Male	37	Right kidney	5.0 cm	F2	pT1bNXMXG2	Stage I
17420-b99 Spain	Female	58	Left kidney	7.0 cm	F1	PT1bNXMXG1	Stage I
09065-b98 Spain	Female	30	Left kidney	1.0 cm	F1	pT1aNXMXG1	Stage I
03532-b97 Spain	Male	45	Right kidney	3.5 cm	F2	pT1aNXMXG2	Stage I
12256-b96 Spain	Male	66	Right kidney	3.0 cm	F2	pT1aNXMXG2	Stage I
11048-b00 Spain	Male	37	Right kidney	5.0 cm	F2	pT1bNXMXG2	Stage I
16214-b99 Spain	Female	78	Right kidney	7.0 cm	F 2	pT1bNXMXG2	Stage I
04069-b98 Spain	Male	65	Right kidney	8.0 cm	F2	pT2NXMXG2	Stage II
01197-b03 Spain	Male	36	Right kidney	7.0 cm	F2	pT1bNXMXG2	Stage I
12424-b02 Spain	Male	70	Left kidney	5.0 cm	F2	pT1bNXMXG2	Stage I
15095-b00 Spain	Female	44	Left kidney	3.5 cm	F1	pT1aNXMXG1	Stage I
08183-b92 Spain	Male	73	Left kidney	5.0 cm	F1	pT1bNXMXG1	Stage I
11212-b94 Spain	Male	47	Right kidney	3.0 cm	F1	pT1aNXMXG1	Stage I
426CE-03 Argentina	Female	68	Left kidney	4.0 cm	F1	pT1aNXMXG1	Stage I

Our data and information from the literature(1-17) indicate that MCRCC appears to be a peculiar variant of clear cell RCC, with very low potential if any for recurrence or metastasis, and a 5-year disease-specific survival rate of 100%. Surgery is curative. It is our belief that the lesion should be renamed as to indicate the benign nature of this tumor. Renal Cell Cystadenoma would be an appropriate one.

References
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El 12/3/2004 12:41, Mirta Garcia Jardon dijo: