Small Renal Tumor Biopsies After Cryoablation Therapy
Small Renal Tumor Biopsies After Cryoablation Therapy
We evaluated 50 biopsy specimens of cryoablated renal tumors. Patients' mean age was 55 years (range, 24–85 years). The mean tumor size was 2.7 cm (range, 1.9–3.5 cm). The mean size of the biopsy specimen was 0.8 cm (range, 0.2–2.3 cm). The diagnosis of tumor was rendered in 33 (66%) cases; 17 (34%) cases displayed normal renal cortical/medullary parenchyma.
The tumor type was determined in 91% of diagnostic cases (30/33) as follows: clear cell renal cell carcinoma (CCRCC), 48.5% (16/33); papillary renal cell carcinoma (RCC), 27.3% (9/33); AML, 9% (3/33); RT with eosinophilic cytoplasm, 11.4% (3/33); oncocytoma, 3% (1/33); and follicular lymphoma, 3% (1/33). RT with eosinophilia or eosinophilic cytoplasm is a descriptive terminology for tumors not classifiable further into other subtypes.
The freeze-associated changes Image 1A and Image 1B included distorted collapsed tumor architecture in portion(s) of the biopsy specimen with crowded foci showing increased nuclear density and indistinct cytoplasmic borders. Also noted were occasional swollen cells with a deeply eosinophilic cytoplasm. Some foci retained clear cell morphology in cases of CCRCC. Partially preserved tumor architecture was also identified focally in most biopsy specimens, facilitating the diagnosis, as described below for each tumor subtype.
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Image 1.
Cryoablation effect. A, Collapsed and crowded architecture with increased nuclear density in lower portion and identifiable clear cell morphology (asterisk) in upper portion of the image (H&E, ×200). B, Higher magnification showing increased nuclear density and cytoplasmic eosinophilia (asterisk) and swollen cytoplasm (asterisk) (H&E, ×400).
The changes in nuclear morphology secondary to cryoablation affected nuclear grading. This consisted of shrunken hyperchromatic nuclei, with a smudgy chromatin pattern causing difficulty in assessing nucleoli at low power; diffuse or focal mild irregularity of nuclear membranes; and nuclear crowding/overlapping due to cytoplasmic damage. FNG I was not given in any biopsy specimen due to nondiscernible nuclear features at ×10 and likely artifactual size variation, making it difficult to exclude nuclear grade II in these specimens. Due to unrevealing nuclear characteristics at low magnification and difficulties in assessing subtle nuclear size difference (as required by the Fuhrman system for the distinction between FNG I and II), an LNG was suggested in 75% (21/28) of the cases Image 2A and Image 2B. Focally identifiable or preserved nuclear details were noted in 25% (7/28) of the cases, and as per Fuhrman criteria, FNG II or III was assigned.
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Image 2.
Low nuclear grade. A, Low magnification showing small shrunken hyperchromatic nuclei with difficult to assess chromatin and nucleolar details (H&E, ×100). B, Higher magnification showing mild irregularity of nuclear membranes and hyperchromasia (H&E, ×400).
In our series, excluding AMLs, oncocytoma, and follicular lymphoma, 28 of 33 tumors (16 CCRCCs, nine papillary RCCs, and three RTs with eosinophilic cytoplasm) were assigned a nuclear grade, as depicted in Table 2.
In 60.6% (20/33) of the cases, immunohistochemistry was performed to assist or confirm the diagnosis. The immunohistochemical stains used included CD10, CK7, EMA, vimentin, AMACR/p504S, HMB-45, Melan-A, SMA, CD31, and lymphoma markers in one case of follicular lymphoma. The tumor cells maintained the staining characteristics expected with each tumor subtype.
CCRCC. The preserved areas in cases of CCRCC were small, which showed nests of cells with a sinusoidal vascular pattern Image 3A. The tumor showed cells with clear cytoplasm at least focally (Image 1A, asterisk). The tumor cells expressed CD10 (Image 3A, inset) in both preserved and distorted areas. The tumor cells were also positive for epithelial membrane antigen (EMA) and RCC antigen.
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Image 3.
Tumor subtypes. A, Clear cell renal cell carcinoma (RCC) with sinusoidal vascular pattern and cells showing clear cytoplasm and small hyperchromatic nuclei (H&E, ×200). Inset: CD10 immunostain, ×400. B, Papillary RCC type I, papillary architecture and fibrovascular stalk with foamy macrophages, small nuclei (H&E, ×400). Inset: CK7 immunostain, ×400. C, Papillary RCC type II, papillary architecture with fibrovascular core showing calcification (arrow), lined by larger cells with eosinophilic cytoplasm (H&E, ×400). D, Oncocytoma. Nested architecture in loose hypocellular fibrocollagenous stroma (H&E, ×200). E, Angiomyolipoma with triphasic morphology, spindled smooth muscle cells, vascular (asterisk) and lipomatous (arrow) components (H&E, ×200). Inset: SMA immunostain, ×400). F, Renal tumor with eosinophilic cytoplasm, poorly preserved tumor focus (H&E, ×200).
Papillary RCC. These showed focally preserved fibrovascular stalks containing foamy macrophages Image 3B in most cases, with increased tumor nuclear density. The immunohistochemical stain for CK7 (Image 3B, inset) showed diffuse strong reactivity, supporting the diagnosis. AMACR/p504S staining performed in a small percentage of biopsy specimens was positive. Four of nine (44.5%) were favored to be type I (Image 3B), one of nine (11%) was type II Image 3C, and the rest (44.5%) could not be reliably distinguished between the two types due to excessive freezing effect.
Oncocytoma. Oncocytoma Image 3D showed focal nested morphology in loose hypocellular stroma in preserved areas and also foci of overlapping nuclei in distorted areas. The nuclei in preserved foci were round and hyperchromatic with a smudgy appearance. Prominent nucleoli were not identifiable. The cytoplasm appeared deeply eosinophilic and granular at a higher magnification.
AML. The AML Image 3E showed triphasic morphology (spindled smooth muscle, vascular and lipomatous components) in two cases and epithelioid morphology in one case. Areas of cellular crowding were present. Immunostains for HMB-45 and/or Melan-A showed focal staining, and SMA (Image 3E, inset) showed diffuse staining in the smooth muscle component.
RT With Eosinophilic Cytoplasm. Three cases were given this descriptive diagnosis, which showed a sheet of eosinophilic tumor cells with no preserved identifiable tumor architecture Image 3F. The cellular and nuclear morphology could not be characterized further due to paucity of diagnostic material and freezing artifact. The immunohistochemical interpretation was limited as well due to lack of adequate tissue. The major differential diagnosis in these cases included oncocytoma, chromophobe RCC, eosinophilic variant of CCRCC, and papillary RCC, among others.
Other. A single case of follicular lymphoma was easily identifiable, which showed dense neoplastic lymphoid infiltrate and was classified based on the immunohistochemical staining pattern and fluorescence in situ hybridization study (dual-color, dual-fusion assay) for IgH/BCL2 rearrangement associated with t(14:18)(q32.3;q21).
The biopsy specimens were taken after the first or second freeze cycle (at the time of thawing). The freeze cycles were six minutes long. Thirteen of 50 (26%) biopsy specimens were taken after the first freeze cycle, and 37 (74%) were taken after the second freeze cycle. Most biopsy specimens were taken after the second freeze cycle (25/33 tumor biopsies and 12/17 nondiagnostic biopsies). Tumor types could be identified in both subsets Table 3, Image 4A, and Image 4B.
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Image 4.
Freeze effect (clear cell renal cell carcinoma), two different cases, biopsy after first (A) and second (B) freeze cycle. Both cases show sinusoidal vascular pattern with focal clear cell morphology (H&E).
Perinephric fat was sent as a separate specimen in 74% (37/50) of the specimens. In none of the cases (0%) was it involved by tumor. Follow-up of all cases of RCC did not show any evidence of tract seeding (mean follow-up of 38.3 months), and none of the masses showed any enhancement by computed tomography (CT) scan, demonstrating no recurrence of vascularized renal masses and thereby effective ablation of the mass.
Results
We evaluated 50 biopsy specimens of cryoablated renal tumors. Patients' mean age was 55 years (range, 24–85 years). The mean tumor size was 2.7 cm (range, 1.9–3.5 cm). The mean size of the biopsy specimen was 0.8 cm (range, 0.2–2.3 cm). The diagnosis of tumor was rendered in 33 (66%) cases; 17 (34%) cases displayed normal renal cortical/medullary parenchyma.
The tumor type was determined in 91% of diagnostic cases (30/33) as follows: clear cell renal cell carcinoma (CCRCC), 48.5% (16/33); papillary renal cell carcinoma (RCC), 27.3% (9/33); AML, 9% (3/33); RT with eosinophilic cytoplasm, 11.4% (3/33); oncocytoma, 3% (1/33); and follicular lymphoma, 3% (1/33). RT with eosinophilia or eosinophilic cytoplasm is a descriptive terminology for tumors not classifiable further into other subtypes.
The freeze-associated changes Image 1A and Image 1B included distorted collapsed tumor architecture in portion(s) of the biopsy specimen with crowded foci showing increased nuclear density and indistinct cytoplasmic borders. Also noted were occasional swollen cells with a deeply eosinophilic cytoplasm. Some foci retained clear cell morphology in cases of CCRCC. Partially preserved tumor architecture was also identified focally in most biopsy specimens, facilitating the diagnosis, as described below for each tumor subtype.
(Enlarge Image)
Image 1.
Cryoablation effect. A, Collapsed and crowded architecture with increased nuclear density in lower portion and identifiable clear cell morphology (asterisk) in upper portion of the image (H&E, ×200). B, Higher magnification showing increased nuclear density and cytoplasmic eosinophilia (asterisk) and swollen cytoplasm (asterisk) (H&E, ×400).
The changes in nuclear morphology secondary to cryoablation affected nuclear grading. This consisted of shrunken hyperchromatic nuclei, with a smudgy chromatin pattern causing difficulty in assessing nucleoli at low power; diffuse or focal mild irregularity of nuclear membranes; and nuclear crowding/overlapping due to cytoplasmic damage. FNG I was not given in any biopsy specimen due to nondiscernible nuclear features at ×10 and likely artifactual size variation, making it difficult to exclude nuclear grade II in these specimens. Due to unrevealing nuclear characteristics at low magnification and difficulties in assessing subtle nuclear size difference (as required by the Fuhrman system for the distinction between FNG I and II), an LNG was suggested in 75% (21/28) of the cases Image 2A and Image 2B. Focally identifiable or preserved nuclear details were noted in 25% (7/28) of the cases, and as per Fuhrman criteria, FNG II or III was assigned.
(Enlarge Image)
Image 2.
Low nuclear grade. A, Low magnification showing small shrunken hyperchromatic nuclei with difficult to assess chromatin and nucleolar details (H&E, ×100). B, Higher magnification showing mild irregularity of nuclear membranes and hyperchromasia (H&E, ×400).
In our series, excluding AMLs, oncocytoma, and follicular lymphoma, 28 of 33 tumors (16 CCRCCs, nine papillary RCCs, and three RTs with eosinophilic cytoplasm) were assigned a nuclear grade, as depicted in Table 2.
In 60.6% (20/33) of the cases, immunohistochemistry was performed to assist or confirm the diagnosis. The immunohistochemical stains used included CD10, CK7, EMA, vimentin, AMACR/p504S, HMB-45, Melan-A, SMA, CD31, and lymphoma markers in one case of follicular lymphoma. The tumor cells maintained the staining characteristics expected with each tumor subtype.
Changes in Each Tumor Type
CCRCC. The preserved areas in cases of CCRCC were small, which showed nests of cells with a sinusoidal vascular pattern Image 3A. The tumor showed cells with clear cytoplasm at least focally (Image 1A, asterisk). The tumor cells expressed CD10 (Image 3A, inset) in both preserved and distorted areas. The tumor cells were also positive for epithelial membrane antigen (EMA) and RCC antigen.
(Enlarge Image)
Image 3.
Tumor subtypes. A, Clear cell renal cell carcinoma (RCC) with sinusoidal vascular pattern and cells showing clear cytoplasm and small hyperchromatic nuclei (H&E, ×200). Inset: CD10 immunostain, ×400. B, Papillary RCC type I, papillary architecture and fibrovascular stalk with foamy macrophages, small nuclei (H&E, ×400). Inset: CK7 immunostain, ×400. C, Papillary RCC type II, papillary architecture with fibrovascular core showing calcification (arrow), lined by larger cells with eosinophilic cytoplasm (H&E, ×400). D, Oncocytoma. Nested architecture in loose hypocellular fibrocollagenous stroma (H&E, ×200). E, Angiomyolipoma with triphasic morphology, spindled smooth muscle cells, vascular (asterisk) and lipomatous (arrow) components (H&E, ×200). Inset: SMA immunostain, ×400). F, Renal tumor with eosinophilic cytoplasm, poorly preserved tumor focus (H&E, ×200).
Papillary RCC. These showed focally preserved fibrovascular stalks containing foamy macrophages Image 3B in most cases, with increased tumor nuclear density. The immunohistochemical stain for CK7 (Image 3B, inset) showed diffuse strong reactivity, supporting the diagnosis. AMACR/p504S staining performed in a small percentage of biopsy specimens was positive. Four of nine (44.5%) were favored to be type I (Image 3B), one of nine (11%) was type II Image 3C, and the rest (44.5%) could not be reliably distinguished between the two types due to excessive freezing effect.
Oncocytoma. Oncocytoma Image 3D showed focal nested morphology in loose hypocellular stroma in preserved areas and also foci of overlapping nuclei in distorted areas. The nuclei in preserved foci were round and hyperchromatic with a smudgy appearance. Prominent nucleoli were not identifiable. The cytoplasm appeared deeply eosinophilic and granular at a higher magnification.
AML. The AML Image 3E showed triphasic morphology (spindled smooth muscle, vascular and lipomatous components) in two cases and epithelioid morphology in one case. Areas of cellular crowding were present. Immunostains for HMB-45 and/or Melan-A showed focal staining, and SMA (Image 3E, inset) showed diffuse staining in the smooth muscle component.
RT With Eosinophilic Cytoplasm. Three cases were given this descriptive diagnosis, which showed a sheet of eosinophilic tumor cells with no preserved identifiable tumor architecture Image 3F. The cellular and nuclear morphology could not be characterized further due to paucity of diagnostic material and freezing artifact. The immunohistochemical interpretation was limited as well due to lack of adequate tissue. The major differential diagnosis in these cases included oncocytoma, chromophobe RCC, eosinophilic variant of CCRCC, and papillary RCC, among others.
Other. A single case of follicular lymphoma was easily identifiable, which showed dense neoplastic lymphoid infiltrate and was classified based on the immunohistochemical staining pattern and fluorescence in situ hybridization study (dual-color, dual-fusion assay) for IgH/BCL2 rearrangement associated with t(14:18)(q32.3;q21).
Effect of the Freeze Cycle
The biopsy specimens were taken after the first or second freeze cycle (at the time of thawing). The freeze cycles were six minutes long. Thirteen of 50 (26%) biopsy specimens were taken after the first freeze cycle, and 37 (74%) were taken after the second freeze cycle. Most biopsy specimens were taken after the second freeze cycle (25/33 tumor biopsies and 12/17 nondiagnostic biopsies). Tumor types could be identified in both subsets Table 3, Image 4A, and Image 4B.
(Enlarge Image)
Image 4.
Freeze effect (clear cell renal cell carcinoma), two different cases, biopsy after first (A) and second (B) freeze cycle. Both cases show sinusoidal vascular pattern with focal clear cell morphology (H&E).
Perinephric fat was sent as a separate specimen in 74% (37/50) of the specimens. In none of the cases (0%) was it involved by tumor. Follow-up of all cases of RCC did not show any evidence of tract seeding (mean follow-up of 38.3 months), and none of the masses showed any enhancement by computed tomography (CT) scan, demonstrating no recurrence of vascularized renal masses and thereby effective ablation of the mass.
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