PMC10200912_01
Imaging features of the left renal lesion. (A. February 28, 2013) Ultrasound revealed the cystic echogenic mass measuring 6.4 x 5.5 cm. (B. April 1, 2017) CT scan showed the cystic lesion of 9.5 x 7.6 x 6.7 cm. (C. October 22, 2019) CT scan showed the cystic lesion of 10.0 x 8.2 cm in cross-section with partial cyst wall calcification. Dynamic contrast-enhanced CT was performed to show the features of the lesion in UP (D, G), CMP (E, H), and NP (F, I). (D-F on May 28, 2020) A mixed-density mass dominated by low density was found in the left kidney, with a cross-section of 10.3 x 8.5 cm and multiple high-density patches at the edge. (G-I on June 15, 2020) With localized encapsulated gas and effusion, the left kidney was partially absent accompanied by marginal densification. Abbreviations: UP, unenhanced phase; CMP, corticomedullary phase; NP, nephrographic phase.
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The objective data showed the cystic lesion measuring 6.4 x 5.5 cm in 2013, 9.5 x 7.6 cm in 2017, and 10.0 x 8.2 cm in 2019 with partial cyst wall calcification ( Figures 1A-C ). An admission dynamic contrast-enhanced CT revealed a mixed-density mass dominated by low density in the left kidney, measuring 10.3 x 8.5 cm in cross-section, with multiple high-density patches at the rim ( Figures 1D-F ,  eFigure 1 ). A CT scan of the head and chest showed no evidence of metastasis, and a repeated abdominal CT scan revealed a localized encapsulation of gas and effusion ( Figures 1G-I ).
Pathological features of the lesion. (A) Massive mucus was found in the fibrocyst wall, and the tumor cells were scattered or glandular in arrangement (HE, x100). (B) A few mucinous adenocarcinoma cells with multiple mucinous foci and scattered calcifications were found in the cystic wall (HE, x100). (C) Strong positivity for PCK (x100). (D) Strong positivity for Villin (x100). (E) Strong positivity for CDX2 (x100). (F) Partial positivity for SATB2 (x100). (G) Weak positivity for Syn (x100). (H) Fifty percent positivity for Ki67 (x100).
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Microscopically, extensive mucus was found in the fibrocyst wall, and the tumor cells were scattered or glandular in arrangement ( Figure 2A ). Immunohistochemistry (IHC) demonstrated that the tumor cells were positive for PCK, Villin, CDX2, SATB2 (some cells), Syn (a few cells), and Ki67 (50%) but negative for CgA, Napsin A, TTF-1, GATA-3, CK7, PAX-8, CA9, RCC, and P63. ( Figures 2C-H ,  eFigure 2 ). Histopathological examination demonstrated fibrous cystic tissue in the renal parenchyma ( Figure 2B ).
General manifestation of the specimen. (A, B) The cystic tumor was seen under the renal capsule and the cut surface was gray, with necrotic tissue.
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In gross specimen examination, a cystic mass of approximately 6.0 x 5.0 x 5.0 cm was seen immediately within the renal capsule with no visible invasion of the collecting system ( Figure 3 ). The levels of the tumor markers gradually decreased after subsequent treatments during follow-up ( eFigure 3 ).
Regular dynamic contrast-enhanced CT scan manifestations in CMP (A, C, E) and NP (B, D, F). (A, B on July 24, 2020) An 8.0 x 5.7 cm cystic low-density lesion was found in the original left renal area. (C, D on August 2, 2021) The cystic effusion was absorbed completely. (E, F on August 17, 2022) The original left kidney area was filled with intestines. Abbreviations: CMP, corticomedullary phase; NP, nephrographic phase.
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One month after the radical surgery, a dynamic contrast-enhanced CT scan revealed a cystic lesion in the original left kidney area measuring 8.0 x 5.7 cm in cross-section ( Figures 4A, B ). Periodic dynamic contrast-enhanced CT scans showed a gradual reduction in the cystic lesion in the left renal region, and a re-examination on August 2, 2021, showed that the lesions had disappeared ( Figures 4C, D ). Until this report, the patient remained stable with outpatient follow-up for 30 months and no evidence of recurrence ( Figures 4E, F ). The timeline of interventions and outcomes for the patient is presented in  eFigure 4 .