Clear cell renal cell carcinoma with cystic component similar to multilocular cystic renal neoplasm of low malignant potential: a rare pattern of cyst-dependent progression from multilocular cystic renal neoplasm of low malignant potential

Background For clear cell renal cell carcinoma (ccRCC) with cystic component similar to multilocular cystic renal neoplasm of low malignant potential (MCRN-LMP) and solid low-grade component simultaneously, we propose the designation “ccRCC with cystic component similar to MCRN-LMP” and to study the relationship between MCRN-LMP and it. Methods Twelve cases of MCRN-LMP and 33 cases of ccRCC with cystic component similar to MCRN-LMP were collected from 3,265 consecutive RCCs to compare them in clinicopathological features, immunohistochemical findings (PAX8, CA-IX, CK7, Vimentin, CD10, P504s, TFE3, 34βE12) and prognosis. Results There was no significant difference in age, sex ratio, tumor size, treatment, grade and stage between them ( P > 0.05). All ccRCCs with cystic component similar to MCRN-LMP coexisted with MCRN-LMP and solid low-grade ccRCCs, and MCRN-LMP component ranged from 20 to 90% (median, 59%). The positive ratio of CK7 and 34βE12 in MCRN-LMPs and ccRCCs’ cystic parts was significantly higher than that in ccRCCs’ solid parts, but the positive ratio of CD10 in MCRN-LMPs and ccRCCs’ cystic parts was significantly lower than that in ccRCCs’ solid parts ( P < 0.05). There was no significant difference of all immunohistochemistry profiles between MCRN-LMPs and ccRCCs’ cystic parts ( P > 0.05). No patient developed recurrence or metastasis. Conclusions MCRN-LMP and ccRCC with cystic component similar to MCRN-LMP have similarity and homology in clinicopathological features, immunohistochemical findings and prognosis, and form a low-grade spectrum with indolent or low malignant potential behavior. The ccRCC with cystic component similar to MCRN-LMP may be a rare pattern of cyst-dependent progression from MCRN-LMP.