Introduction

Multilocular cystic renal neoplasm of low malignant potential (MCRN-LMP) is a rare cystic tumor of the kidney with an excellent outcome and is composed of multiple cysts separated by thick septa covered with clear cells (1,2). It was defined as “a tumour composed entirely of numerous cysts, the septa of which contain small groups of clear cells indistinguishable from grade 1 clear cell carcinoma” by Eble et al. (3), in the 2004 World Health Organization (WHO) histological classification of tumours of the kidney.

MCRN-LMP has been classified as a neoplasm with an intrinsically cystic growth pattern, and no, or at most little, malignant potential by Eble and Bonsib (4). They have suggested the following 3 criteria to be associated with this low-grade malignant potential; 1- an expansile mass surrounded by a fibrous wall, 2- the interior of the tumor entirely composed of cysts and septa with no expansile solid nodules, and 3- the septa containing aggregates of epithelial cells with clear cytoplasm (4).

The largest published series of MCRN-LMP by Li et al. (5) included 76 subjects. 66 patients were followed up for median of 52 months. No recurrence was observed. A patient died due to rectal cancer, but no metastasis or recurrence of renal tumor was detected (5). Nassir et al. (6) has defined MCRN-LMP as a cystic lesion with neoplastic clear cells, an uncommon subtype of conventional clear cell renal cell carcinoma (ccRCC), and as having a benign clinical course. Murad et al. (7) has reported their ten-year experience of 6 cases of MCRN-LMP that were followed for a minimum of 2 years. Neither recurrence nor metastasis was observed. They have concluded that the tumor was a low-grade variant of renal cell carcinoma (7).

In 2016, WHO published a new classification of renal tumors as new data were collected (8). Due to its excellent prognosis from multiple publications (1,9,10), these tumors are now termed as “MCRN-LMP” (11).

A 70-year-old male presented to the Urology Department of Medical Faculty of Marmara University with the complaints involving lower urinary system. Magnetic resonance imaging demonstrated a solid mass of 58 mm on the lower pole of the left kidney and a multilocular cyst of 20 mm about 40 mm away from it. Left partial nephrectomy was performed. On pathological examination the partial nephrectomy material measured 60x60x50 mm. A yellow-gray solid tumor with well defined borders and of 5 cm in diameter was present in the nephrectomy material. A second material measuring 25x15x15 mm from the kidney was examined and a multilocular cyst with a diameter of 15 mm was observed. The tissue specimens were fixed in 10% buffered formaldehyde solution and embedded in paraffin. Tissue sections were stained with haematoxylin and eosin. Grade 2 cells with clear cytoplasm were observed in the solid tumor. Immunohistochemically, the cells demonstrated positive staining for CD10 and vimentin. The cystic lesion was composed of multiple cysts separated by thin septa and the inner surface of the cysts was lined by cells with clear cytoplasm. There were a few cell clusters in the septa (Figure 1, 2). These cells were grade 1 and demonstrated positive staining for cytokeratin 7, PAX-8 and epithelial membrane antigen but negative staining for CD10 (Figure 3, 4). The solid mass was diagnosed as ccRCC and the cystic lesion as the multilocular cystic renal neoplasm of low malignant potential.

Suzigan et al. (11) has proposed that MCRN-LMP should be renamed and reclassified to draw attention to its benign nature. They have suggested the term “multilocular cystic renal cell neoplasm of low malignant potential” for this lesion in 2006. They have believed that this new terminology might help the urologists approach the patients conservatively (11).

The International Society of Uropathology, has separated ccRCC from MCRN-LMP, according to the current data, and clearly defined MCRN-LMP as a least aggressive neoplasm with no recurrence and no metastatic potential after surgical treatment (12).

The terminology has changed and so called “multilocular cystic renal cell carcinoma” is currently named as multilocular cystic renal neoplasm of low malignant potential in the International Society of Urological Pathology Vancouver Classification of Renal Neoplasia and the 2016 World Health Organization Classification of Tumors of the Urinary System and Male Genital Organs (13).

Keywords: Multilocular, neoplasia, renal tumor

Anahtar Kelimeler: Multiloküler, neoplazi, renal tümör

Ethics

Peer-review: Internally peer-reviewed.

Authorship Contributions

Surgical and Medical Practices: Deniz Filinte, İlker Tinay, Concept: Deniz Filinte, Design: Deniz Filinte, Data Collection or Processing: Deniz Filinte, Analysis or Interpretation: Deniz Filinte, Literature Search: Deniz Filinte, Writing: Deniz Filinte.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial disclosure: The authors declared that this study received no financial support.