- Email: [email protected]
Rhabdoid differentiation of chromophobe renal cell carcinoma
Pathology (2003) 35, pp. 228–230
ANATOMICAL PATHOLOGY
Rhabdoid differentiation of chromophobe renal cell carcinoma BEVERLEY A. SHANNON*
AND
RONALD J. COHEN{
Pathology Downloaded from informahealthcare.com by Nyu Medical Center on 07/21/15 For personal use only.
*Tissugen Pty Ltd; {Uropath Pty Ltd, Perth, Western Australia
Summary Aims: Rhabdoid change represents an aggressive form of divergent differentiation previously reported in conventional (clear-cell) and papillary renal cell carcinoma. This study aims to characterise rhabdoid differentiation in a case of chromophobe renal cell carcinoma (ChRCC) and to investigate its origin by genetic analysis. Methods: A large tumour mass arising in the right kidney of a 76-year-old male was investigated using routine stains (H&E, Hale’s colloidal iron), immunostains (vimentin, cytokeratin) and genetic analysis for loss of heterozygosity (LOH) on chromosomes 1, 2, 3p, 6q, 10q, 13q, 17q, 17p and 21q. Results: The tumour mass was comprised of the following histological subtypes: (i) typical ChRCC, (ii) eosinophilic variant ChRCC and (iii) rhabdoid variant RCC. Tumour cells of all three different histological subtypes had a positive reaction to Hale’s colloidal iron stain, negative immunostaining for vimentin and LOH on chromosomes 2, 10q, 13q and 17p. These results are consistent with a diagnosis of ChRCC and indicate a common genetic origin for all three histological cell types. Conclusions: This study confirms that the aggressive rhabdoid variant can arise from ChRCC, as has been previously demonstrated for conventional (clear-cell) and papillary RCC. Key words: Rhabdoid differentiation, chromophobe renal cell carcinoma, kidney.
with loss of heterozygosity (LOH) at chromosomes 1, 2, 6, 10, 13, 17 and 21.5 ChRCC has a considerably better prognosis compared with conventional (clear-cell) RCC,2,3,6 however, it is important to recognise variant cases that may behave in an aggressive manner. These include ChRCC larger than 8 cm, chromophobe tumours associated with papillary RCC7 and ChRCC with sarcomatoid change,8,9 an aggressive form of divergent differentiation known to occur in all RCC subtypes.10 A second aggressive form of divergent differentiation, described as rhabdoid change, has recently been reported in papillary and conventional (clear-cell) RCC11,12 where it is similarly associated with poor prognosis. Extensive review of the literature (PubMed search, May 2002), and publications cited in our previous study,12 indicate this case to be the first report of ChRCC with rhabdoid differentiation.
CASE REPORT A 79-year-old male underwent radical nephrectomy for a radiologically detected tumour mass in the mid-zone of the right kidney, which compressed the renal pelvis. The tumour did not appear to have extrarenal extension or involvement of the renal vein, ureter or artery. The patient made an uneventful recovery and at 3 months remained alive and well with no evidence of recurrence or metastasis.
Received 13 June 2002, revised 22 July 2002, accepted 22 July 2002
INTRODUCTION Chromophobe renal cell carcinoma (ChRCC) is a distinct tumour type with two histological variants. Typical ChRCC is predominantly comprised of large polygonal cells with abundant, pale, reticular cytoplasm and peripheral condensation that produces well-defined cell borders (plant-cell-like). The less common eosinophilic ChRCC variant is composed mainly of smaller, eosinophilic tumour cells containing numerous mitochondria.1–3 These two cell types may co-exist, with foci of eosinophilic cells often seen in typical chromophobe tumours. Conversely, occasional typical chromophobe cells may be observed in eosinophilic variant tumours.4 Ultrastructurally, ChRCC is characterised by an accumulation of cytoplasmic microvesicles.3,4 These are believed to originate from outpouchings of the mitochondrial membrane3 and are associated with a positive reaction to Hale’s colloidal iron stain.3,4 Genetically, ChRCC is associated
MATERIALS AND METHODS Tumour samples for histological examination were fixed in 4% buffered formaldehyde and embedded in paraffin. Four-mm sections were assessed by routine stains (H&E, Hale’s colloidal iron) and immunostains for vimentin (1:50; Dako, Denmark) and cytokeratin (AE1/AE3, 1:50; Dako). For genetic analysis, paraffin-embedded samples of typical chromophobe tumour, eosinophilic chromophobe tumour, rhabdoid chromophobe tumour and normal kidney tissue were dewaxed in xylene and DNA prepared as previously described.13 Loss of heterozygosity (LOH) was determined by radiolabelled polymerase chain reaction (PCR) amplification of polymorphic microsatellite markers as previously described.14 Markers used in this study were D1S2883 (chromosome 1), TPOX (chromosome 2), D3S1539 (3p22.5–3pter), D6S305 (6q27), D10S1239 (10q23–10q24), D13S317 (13q22), D17S885 (17q12–17q21), D17S559 (17p13) and DS21S267 (21q22.1–21q22.3). Allelic dosage was determined by scanning of autoradiographs and density profiling using Scion Image Software (Scion Corporation, USA), with LOH defined as at least 50% reduction in intensity for one allele in tumour tissue compared with that allele in normal kidney tissue.
ISSN 0031-3025 printed/ISSN 1465–3931 online/03/030228–03 # 2003 Royal College of Pathologists of Australasia DOI: 10.1080/0031302031000123209
RHABDOID DIFFERENTIATION OF CRCC
229
RESULTS
Pathology Downloaded from informahealthcare.com by Nyu Medical Center on 07/21/15 For personal use only.
Macroscopic features A tumour mass measuring 58648654 mm was noted in the mid-portion of the right kidney. The main tumour mass was copper coloured with small haemorrhagic areas, while two distinct pale solid tumour masses (larger than 28 mm in diameter) were noted adjacent to the main tumour and bulged into the renal hilum (Fig. 1). Microscopic and genetic features Microscopic examination confirmed a tumour with varied histology. The main tumour mass was comprised of large polygonal cells with abundant, pale, reticular cytoplasm and prominent cell borders (Fig. 2), characteristic of typical ChRCC. In other regions, the tumour was composed of smaller cells with brightly eosinophilic cytoplasm and small nuclei that showed little pleomorphism or mitotic activity (Fig. 3). These features are consistent with eosinophilic variant ChRCC cells. In contrast, the solid white tumour masses recognised macroscopically were composed of large, mitotically active polygonal cells with abundant eosinophilic cytoplasm and large atypical pleomorphic nuclei with prominent nucleoli (Fig. 3). These cells were morphologically identical to the rhabdoid variant cells recently described11,12 in association with conventional (clear-cell) and papillary RCC. Positive reaction to Hale’s colloidal iron stain and negative immunostaining for vimentin was shown for the typical chromophobe, eosinophilic chromophobe and the rhabdoid variant cells. LOH on chromosomes 2, 10q23–10q24, 13q22 and 17p13 was also detected in all variant tumour samples.
Fig. 2 Transition between typical chromophobe renal cell carcinoma (right) and rhabdoid variant (left) (H&E, original magnification, 6100). More detailed morphology is shown for the typical chromophobe (right insert) and rhabdoid (left insert) tumour cells (H&E, original magnification, 6200).
Fig. 3 Comparison between pleomorphic rhabdoid variant cells (left) and the uniform eosinophilic CRCC variant cells (right). Eosinophilic ‘rhabdoid’ inclusions (arrow) are easily identified with routine stains (H&E, original magnification, 6200).
DISCUSSION
Fig. 1 Macroscopic appearance of the tumour mass showing regions of typical chromophobe renal cell carcinoma (C) and adjacent rhabdoid areas (R).
ChRCC is a distinct tumour type with two known histological variants. Both the typical and eosinophilic ChRCC variants are distinguished from other RCC subtypes by a combination of factors including characteristic histological features, a positive reaction to Hale’s colloidal iron, negative immunostaining for vimentin and LOH at chromosomes 1, 2, 6, 10, 13, 17 and 21.2–6 ChRCC is generally associated with a good prognosis;2,3,6 however, it is important to identify cases that may have a poor outcome, such as ChRCC involving sarcomatoid change.8,9 Rhabdoid change is a similarly aggressive form of divergent differentiation recently described in papillary and conventional (clear-cell) RCC.11,12 We now describe a case of rhabdoid differentiation in ChRCC. On histological examination this tumour was identified as a typical chromophobe tumour with small foci of eosinophilic variant cells. In addition, we identified a region of divergent differentiation with large, high-grade
Pathology Downloaded from informahealthcare.com by Nyu Medical Center on 07/21/15 For personal use only.
230
Pathology (2003), 35, June
SHANNON AND COHEN
malignant cells containing abundant eosinophilic cytoplasm (rhabdoid cells). The rhabdoid cells in our present study were positive for Hale’s colloidal iron stain, negative for vimentin immunostaining and had LOH at chromosomes 2, 10, 13 and 17. These features were also shown in the typical and eosinophilic chromophobe cells, which is consistent with a diagnosis of ChRCC2–6 and confirms that the rhabdoid variant cells share a common genetic origin with the chromophobe tumour cells. Previous work11,12 has found that rhabdoid cells in RCC stain positively for vimentin. However, those studies involved rhabdoid differentiation of papillary and conventional (clear-cell) tumours in most cases, thus the presence of vimentin probably reflects the origin of those rhabdoid cells. Chromophobe tumour cells, as a rule, do not contain vimentin;2,3 therefore, it is reasonable to expect that rhabdoid cells arising in chromophobe tumours are also negative for vimentin. It is important to note that the rhabdoid appearance of these cells in RCC can be due to various factors including condensations of intermediate filaments and paranuclear aggregates of organelle-laden cytoplasm.11 Given that eosinophilic variant ChRCC cells contain numerous mitochondria,1–3 it is likely that the rhabdoid morphology of the variant chromophobe cells described in this study is due to aggregations of mitochondria. Regardless of the ultrastructural cause, rhabdoid morphology in conventional (clear-cell) and papillary RCC is associated with high tumour grade, early metastasis and poor prognosis.11,12 Our results indicate that rhabdoid differentiation can also occur in ChRCC and, along with sarcomatoid change, may represent an aggressive variant of this RCC subtype. Longer-term follow-up and further cases are required to assess the prognostic importance of rhabdoid differentiation in ChRCC. ACKNOWLEDGEMENTS We acknowledge the Hollywood Research Foundation for its assistance in funding this
study, Mr Alistair Tulloch for referral of this case to our attention and Dr Jacqueline Bentel (Department of Pathology, Royal Perth Hospital) for conducting the LOH analysis. Address for correspondence: Dr R. J. Cohen, Uropath Pty Ltd, 41 Hampden Road, Nedlands, WA 6009, Australia. E-mail: [email protected]
References 1. Thoenes W, Storkel S, Rumpelt H. Human chromophobe cell renal carcinoma. Virchows Arch B (Cell Pathol) 1985; 48: 207–17. 2. Thoenes W, Storkel S, Rumpelt H, et al. Chromophobe cell renal carcinoma and its variants – a report on 32 cases. J Pathol 1988; 155: 277–87. 3. Akhtar M, Kardar H, Linjawi T, et al. Chromophobe cell carcinoma of the kidney: a clinicopathologic study of 21 cases. Am J Surg Pathol 1995; 19: 1245–56. 4. Latham B, Dickersin R, Oliva E. Subtypes of chromophobe cell renal carcinoma: an ultrastructural and histochemical study of 13 cases. Am J Surg Pathol 1999; 23: 530–5. 5. Kovacs G, Akhtar M, Beckwith B, et al. The Heidelberg classification of renal cell tumours. J Pathol 1997; 183: 131–3. 6. Crotty T, Farrow G, Lieber M. Chromophobe cell renal carcinoma: clinicopathological features of 50 cases. J Urol 1995; 154: 964–7. 7. Renshaw A, Henske E, Loughlin K, et al. Aggressive variants of chromophobe renal cell carcinoma. Cancer 1996; 78: 1756–61. 8. Hirokawa M, Shimizu M, Sakurai T, et al. Sarcomatoid renal cell carcinoma with chromophobe cell foci. APMIS 1998; 106: 993–6. 9. de Peralta-Venturina M, Moch H, Amin M, et al. Sarcomatoid differentiation in renal cell carcinoma: a study of 101 cases. Am J Surg Pathol 2001; 25: 275–84. 10. Delahunt B. Sarcomatoid renal carcinoma: the final common dedifferentiation pathway of renal epithelial malignancies. Pathology 1999; 31: 185–90. 11. Gokden N, Nappi O, Swanson P, et al. Renal cell carcinoma with rhabdoid features. Am J Surg Pathol 2000; 24: 1329–38. 12. Shannon B, Wisniewski S, Bentel J, Cohen RJ. Adult rhabdoid renal cell carcinoma. Arch Pathol Lab Med 2002; 126: 1506–10. 13. Diaz-Cano S, Brady S. DNA extraction from formalin-fixed, paraffinembedded tissues: protein digestion as a limiting step for retrieval of high-quality DNA. Diagn Mol Pathol 1997; 6: 342–6. 14. McCulloch R, Sellner L, Papadimitriou J, et al. The incidence of microsatellite instability and loss of heterogeneity in fibroadenoma of the breast. Breast Cancer Res Treat 1998; 49: 165–9.
ANATOMICAL PATHOLOGY
Rhabdoid differentiation of chromophobe renal cell carcinoma BEVERLEY A. SHANNON*
AND
RONALD J. COHEN{
Pathology Downloaded from informahealthcare.com by Nyu Medical Center on 07/21/15 For personal use only.
*Tissugen Pty Ltd; {Uropath Pty Ltd, Perth, Western Australia
Summary Aims: Rhabdoid change represents an aggressive form of divergent differentiation previously reported in conventional (clear-cell) and papillary renal cell carcinoma. This study aims to characterise rhabdoid differentiation in a case of chromophobe renal cell carcinoma (ChRCC) and to investigate its origin by genetic analysis. Methods: A large tumour mass arising in the right kidney of a 76-year-old male was investigated using routine stains (H&E, Hale’s colloidal iron), immunostains (vimentin, cytokeratin) and genetic analysis for loss of heterozygosity (LOH) on chromosomes 1, 2, 3p, 6q, 10q, 13q, 17q, 17p and 21q. Results: The tumour mass was comprised of the following histological subtypes: (i) typical ChRCC, (ii) eosinophilic variant ChRCC and (iii) rhabdoid variant RCC. Tumour cells of all three different histological subtypes had a positive reaction to Hale’s colloidal iron stain, negative immunostaining for vimentin and LOH on chromosomes 2, 10q, 13q and 17p. These results are consistent with a diagnosis of ChRCC and indicate a common genetic origin for all three histological cell types. Conclusions: This study confirms that the aggressive rhabdoid variant can arise from ChRCC, as has been previously demonstrated for conventional (clear-cell) and papillary RCC. Key words: Rhabdoid differentiation, chromophobe renal cell carcinoma, kidney.
with loss of heterozygosity (LOH) at chromosomes 1, 2, 6, 10, 13, 17 and 21.5 ChRCC has a considerably better prognosis compared with conventional (clear-cell) RCC,2,3,6 however, it is important to recognise variant cases that may behave in an aggressive manner. These include ChRCC larger than 8 cm, chromophobe tumours associated with papillary RCC7 and ChRCC with sarcomatoid change,8,9 an aggressive form of divergent differentiation known to occur in all RCC subtypes.10 A second aggressive form of divergent differentiation, described as rhabdoid change, has recently been reported in papillary and conventional (clear-cell) RCC11,12 where it is similarly associated with poor prognosis. Extensive review of the literature (PubMed search, May 2002), and publications cited in our previous study,12 indicate this case to be the first report of ChRCC with rhabdoid differentiation.
CASE REPORT A 79-year-old male underwent radical nephrectomy for a radiologically detected tumour mass in the mid-zone of the right kidney, which compressed the renal pelvis. The tumour did not appear to have extrarenal extension or involvement of the renal vein, ureter or artery. The patient made an uneventful recovery and at 3 months remained alive and well with no evidence of recurrence or metastasis.
Received 13 June 2002, revised 22 July 2002, accepted 22 July 2002
INTRODUCTION Chromophobe renal cell carcinoma (ChRCC) is a distinct tumour type with two histological variants. Typical ChRCC is predominantly comprised of large polygonal cells with abundant, pale, reticular cytoplasm and peripheral condensation that produces well-defined cell borders (plant-cell-like). The less common eosinophilic ChRCC variant is composed mainly of smaller, eosinophilic tumour cells containing numerous mitochondria.1–3 These two cell types may co-exist, with foci of eosinophilic cells often seen in typical chromophobe tumours. Conversely, occasional typical chromophobe cells may be observed in eosinophilic variant tumours.4 Ultrastructurally, ChRCC is characterised by an accumulation of cytoplasmic microvesicles.3,4 These are believed to originate from outpouchings of the mitochondrial membrane3 and are associated with a positive reaction to Hale’s colloidal iron stain.3,4 Genetically, ChRCC is associated
MATERIALS AND METHODS Tumour samples for histological examination were fixed in 4% buffered formaldehyde and embedded in paraffin. Four-mm sections were assessed by routine stains (H&E, Hale’s colloidal iron) and immunostains for vimentin (1:50; Dako, Denmark) and cytokeratin (AE1/AE3, 1:50; Dako). For genetic analysis, paraffin-embedded samples of typical chromophobe tumour, eosinophilic chromophobe tumour, rhabdoid chromophobe tumour and normal kidney tissue were dewaxed in xylene and DNA prepared as previously described.13 Loss of heterozygosity (LOH) was determined by radiolabelled polymerase chain reaction (PCR) amplification of polymorphic microsatellite markers as previously described.14 Markers used in this study were D1S2883 (chromosome 1), TPOX (chromosome 2), D3S1539 (3p22.5–3pter), D6S305 (6q27), D10S1239 (10q23–10q24), D13S317 (13q22), D17S885 (17q12–17q21), D17S559 (17p13) and DS21S267 (21q22.1–21q22.3). Allelic dosage was determined by scanning of autoradiographs and density profiling using Scion Image Software (Scion Corporation, USA), with LOH defined as at least 50% reduction in intensity for one allele in tumour tissue compared with that allele in normal kidney tissue.
ISSN 0031-3025 printed/ISSN 1465–3931 online/03/030228–03 # 2003 Royal College of Pathologists of Australasia DOI: 10.1080/0031302031000123209
RHABDOID DIFFERENTIATION OF CRCC
229
RESULTS
Pathology Downloaded from informahealthcare.com by Nyu Medical Center on 07/21/15 For personal use only.
Macroscopic features A tumour mass measuring 58648654 mm was noted in the mid-portion of the right kidney. The main tumour mass was copper coloured with small haemorrhagic areas, while two distinct pale solid tumour masses (larger than 28 mm in diameter) were noted adjacent to the main tumour and bulged into the renal hilum (Fig. 1). Microscopic and genetic features Microscopic examination confirmed a tumour with varied histology. The main tumour mass was comprised of large polygonal cells with abundant, pale, reticular cytoplasm and prominent cell borders (Fig. 2), characteristic of typical ChRCC. In other regions, the tumour was composed of smaller cells with brightly eosinophilic cytoplasm and small nuclei that showed little pleomorphism or mitotic activity (Fig. 3). These features are consistent with eosinophilic variant ChRCC cells. In contrast, the solid white tumour masses recognised macroscopically were composed of large, mitotically active polygonal cells with abundant eosinophilic cytoplasm and large atypical pleomorphic nuclei with prominent nucleoli (Fig. 3). These cells were morphologically identical to the rhabdoid variant cells recently described11,12 in association with conventional (clear-cell) and papillary RCC. Positive reaction to Hale’s colloidal iron stain and negative immunostaining for vimentin was shown for the typical chromophobe, eosinophilic chromophobe and the rhabdoid variant cells. LOH on chromosomes 2, 10q23–10q24, 13q22 and 17p13 was also detected in all variant tumour samples.
Fig. 2 Transition between typical chromophobe renal cell carcinoma (right) and rhabdoid variant (left) (H&E, original magnification, 6100). More detailed morphology is shown for the typical chromophobe (right insert) and rhabdoid (left insert) tumour cells (H&E, original magnification, 6200).
Fig. 3 Comparison between pleomorphic rhabdoid variant cells (left) and the uniform eosinophilic CRCC variant cells (right). Eosinophilic ‘rhabdoid’ inclusions (arrow) are easily identified with routine stains (H&E, original magnification, 6200).
DISCUSSION
Fig. 1 Macroscopic appearance of the tumour mass showing regions of typical chromophobe renal cell carcinoma (C) and adjacent rhabdoid areas (R).
ChRCC is a distinct tumour type with two known histological variants. Both the typical and eosinophilic ChRCC variants are distinguished from other RCC subtypes by a combination of factors including characteristic histological features, a positive reaction to Hale’s colloidal iron, negative immunostaining for vimentin and LOH at chromosomes 1, 2, 6, 10, 13, 17 and 21.2–6 ChRCC is generally associated with a good prognosis;2,3,6 however, it is important to identify cases that may have a poor outcome, such as ChRCC involving sarcomatoid change.8,9 Rhabdoid change is a similarly aggressive form of divergent differentiation recently described in papillary and conventional (clear-cell) RCC.11,12 We now describe a case of rhabdoid differentiation in ChRCC. On histological examination this tumour was identified as a typical chromophobe tumour with small foci of eosinophilic variant cells. In addition, we identified a region of divergent differentiation with large, high-grade
Pathology Downloaded from informahealthcare.com by Nyu Medical Center on 07/21/15 For personal use only.
230
Pathology (2003), 35, June
SHANNON AND COHEN
malignant cells containing abundant eosinophilic cytoplasm (rhabdoid cells). The rhabdoid cells in our present study were positive for Hale’s colloidal iron stain, negative for vimentin immunostaining and had LOH at chromosomes 2, 10, 13 and 17. These features were also shown in the typical and eosinophilic chromophobe cells, which is consistent with a diagnosis of ChRCC2–6 and confirms that the rhabdoid variant cells share a common genetic origin with the chromophobe tumour cells. Previous work11,12 has found that rhabdoid cells in RCC stain positively for vimentin. However, those studies involved rhabdoid differentiation of papillary and conventional (clear-cell) tumours in most cases, thus the presence of vimentin probably reflects the origin of those rhabdoid cells. Chromophobe tumour cells, as a rule, do not contain vimentin;2,3 therefore, it is reasonable to expect that rhabdoid cells arising in chromophobe tumours are also negative for vimentin. It is important to note that the rhabdoid appearance of these cells in RCC can be due to various factors including condensations of intermediate filaments and paranuclear aggregates of organelle-laden cytoplasm.11 Given that eosinophilic variant ChRCC cells contain numerous mitochondria,1–3 it is likely that the rhabdoid morphology of the variant chromophobe cells described in this study is due to aggregations of mitochondria. Regardless of the ultrastructural cause, rhabdoid morphology in conventional (clear-cell) and papillary RCC is associated with high tumour grade, early metastasis and poor prognosis.11,12 Our results indicate that rhabdoid differentiation can also occur in ChRCC and, along with sarcomatoid change, may represent an aggressive variant of this RCC subtype. Longer-term follow-up and further cases are required to assess the prognostic importance of rhabdoid differentiation in ChRCC. ACKNOWLEDGEMENTS We acknowledge the Hollywood Research Foundation for its assistance in funding this
study, Mr Alistair Tulloch for referral of this case to our attention and Dr Jacqueline Bentel (Department of Pathology, Royal Perth Hospital) for conducting the LOH analysis. Address for correspondence: Dr R. J. Cohen, Uropath Pty Ltd, 41 Hampden Road, Nedlands, WA 6009, Australia. E-mail: [email protected]
References 1. Thoenes W, Storkel S, Rumpelt H. Human chromophobe cell renal carcinoma. Virchows Arch B (Cell Pathol) 1985; 48: 207–17. 2. Thoenes W, Storkel S, Rumpelt H, et al. Chromophobe cell renal carcinoma and its variants – a report on 32 cases. J Pathol 1988; 155: 277–87. 3. Akhtar M, Kardar H, Linjawi T, et al. Chromophobe cell carcinoma of the kidney: a clinicopathologic study of 21 cases. Am J Surg Pathol 1995; 19: 1245–56. 4. Latham B, Dickersin R, Oliva E. Subtypes of chromophobe cell renal carcinoma: an ultrastructural and histochemical study of 13 cases. Am J Surg Pathol 1999; 23: 530–5. 5. Kovacs G, Akhtar M, Beckwith B, et al. The Heidelberg classification of renal cell tumours. J Pathol 1997; 183: 131–3. 6. Crotty T, Farrow G, Lieber M. Chromophobe cell renal carcinoma: clinicopathological features of 50 cases. J Urol 1995; 154: 964–7. 7. Renshaw A, Henske E, Loughlin K, et al. Aggressive variants of chromophobe renal cell carcinoma. Cancer 1996; 78: 1756–61. 8. Hirokawa M, Shimizu M, Sakurai T, et al. Sarcomatoid renal cell carcinoma with chromophobe cell foci. APMIS 1998; 106: 993–6. 9. de Peralta-Venturina M, Moch H, Amin M, et al. Sarcomatoid differentiation in renal cell carcinoma: a study of 101 cases. Am J Surg Pathol 2001; 25: 275–84. 10. Delahunt B. Sarcomatoid renal carcinoma: the final common dedifferentiation pathway of renal epithelial malignancies. Pathology 1999; 31: 185–90. 11. Gokden N, Nappi O, Swanson P, et al. Renal cell carcinoma with rhabdoid features. Am J Surg Pathol 2000; 24: 1329–38. 12. Shannon B, Wisniewski S, Bentel J, Cohen RJ. Adult rhabdoid renal cell carcinoma. Arch Pathol Lab Med 2002; 126: 1506–10. 13. Diaz-Cano S, Brady S. DNA extraction from formalin-fixed, paraffinembedded tissues: protein digestion as a limiting step for retrieval of high-quality DNA. Diagn Mol Pathol 1997; 6: 342–6. 14. McCulloch R, Sellner L, Papadimitriou J, et al. The incidence of microsatellite instability and loss of heterogeneity in fibroadenoma of the breast. Breast Cancer Res Treat 1998; 49: 165–9.