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Fine needle aspiration cytology of chromophobe renal cell carcinoma. A report of two cases.

Introduction

Chromophobe renal cell carcinoma (ChRCC) is a variant of parenchymal renal cell carcinoma, comprising 2-5% of all renal cell carcinoma and characterised by unique morphological, histochemical, ultrastructural and genetic features (1-5). ChRCC is biologically less aggressive than clear cell renal carcinoma (3,6,7) having a low potential for metastasis mostly to lymph nodes and liver (3). ChRCC can be confused with clear cell renal cell carcinoma or oncocytoma and several non-renal tumours with overlapping features including hepatocellular carcinoma, adrenal cortical carcinoma, lung carcinoma, and oncocytic tumours of salivary gland and thyroid.

We describe the cytologic features of ChRCC diagnosed by FNA in two cases with histochemical, immunohistochemical and cytogenetic findings.

Case reports

Case 1

A 50 year old female was found to have an incidental left renal tumour on investigation for biliary colic. She had no any urinary symptoms or haematuria. An ultrasound scan showed gall stones and a well defined, round 40 x 30 mm solid left renal tumour. FNA of the left kidney mass was performed under ultrasound guidance. After confirmation of a renal cell carcinoma in the left kidney by FNA, laparoscopic left nephrectomy with transvaginal removal of the tumour was performed.

Case 2

A 75 year old female with history of a renal cell carcinoma of the left kidney who now presented with right shoulder pain and a palpable 80 mm soft tissue mass over the anterior chest wall, deep to the skin, three years after nephrectomy. At that time histology of the left kidney revealed a 165 mm chromophobe renal cell carcinoma which did not breach the renal capsule but did demonstrate vascular space invasion and renal sinus invasion. Ultrasound guided FNA of the right anterior chest wall mass was performed. Core biopsy was not performed as the aspirated material was adequate to make a diagnosis.

Materials and methods

On site smears were made from the FNA material in both cases and fixed in 95% ethanol and stained with modified Papanicolaou method and the rest of the material was collected in 30% ethanol in physiologic saline. From half of this material, filter preparations were made on size 5 micron Sartorius AG-cellulose acetate filters using the cytosieve method and stained by the Papanicolaou method. The remainder of the aspirate sample was spun and from the sediment a cell block was made, fixed in 10% formalin, embedded in paraffin, routinely processed and stained with hematoxylin-eosin (H & E).

Immunohistochemical studies were undertaken using antibodies CK7 (1:750 Dako), cytokeratin AE1/AE3 (1:1000 Dako), EMA (1:750 Dako), CD10 (1:300 Novocastra), vimentin (1:4000 Dako), S100 (1:4000 Dako), TTF-1 (1:250 Novocastra) and thyroglobulin (1:500 Dako). Electron microscopy (EM) on cell block sections were unsuccessful but were performed subsequently on sections from primary tumour. FISH analysis on cell block sections also were unsuccessful due to the loss of material but were possible on formalin fixed tissue sections of the primary tumour in the kidneys of both cases.

Results

Cytological findings

Case 1

Smears and filter preparations were cellular and composed of predominant dissociated and occasional clusters of variably sized neoplastic cells, some with uniform granular cytoplasm and some with flocculent cytoplasm having well defined cell borders, round to oval nuclei without nucleoli and irregular nuclear membrane giving a "raisinoid" appearance (Figure 1a). Rare intranuclear inclusions and grooves were noted. Occasional cells with more pleomorphic nuclei were seen. Perinuclear clearing was evident in cell block section (Figure 2a).

Case 2

Smears and filter preparations were cellular, comprising predominantly single cells and small groups of cells in a background of blood. The cells were large, polygonal to round with granular to flocculent cytoplasm and well defined cell borders. The nuclei were vesicular with small or indistinct nucleoli. Perinuclear clearing was a striking finding in most of the cells on smears and cell block (Figures 1b and 2b). Mild nuclear pleomorphism was present. Large bizarre cells, intranuclear pseudoinclusions, marked irregularity of nuclear membranes (raisinoid features) and nuclear grooves were not evident in this case. Also evident were occasional large papillary fragments lined by large cells with abundant clear to vacuolated cytoplasm.

Histological findings

Case 1

The tumour was composed of trabeculae and sheets of neoplastic cells of varying sizes with flocculent cytoplasm and well defined cell borders separated by thin fibrovascular septa. "Raisinoid" nuclei were evident with predominant nuclear grooves, rare intranuclear inclusions and the presence of a perinuclear clear zone (Figure 3a). In addition, throughout the tumour were scattered larger cells with pale cytoplasm. No extra renal extension and vascular invasion was seen.

Case 2

The primary tumour in the kidney was composed of large sheets of neoplastic cells of varying sizes with pale to flocculent cytoplasm, well defined cell borders and perinuclear clear zone separated by thin fibrovascular septa (Figure 3b). Some of the tumour cells had irregular nuclear membrane and inconspicuous nucleoli. Focally papillary fragments of tissue lined by large cells with abundant clear cytoplasm (balloon cells) were noted. Vascular invasion was noted.

Histochemical findings

PAS and PAS-D stains on cell block sections were negative and Hale's colloidal iron stain on sections of cell blocks and primary tumour in both cases were positive showing bright blue cytoplasmic staining in contrast to red nuclei.

Immunohistochemical findings

Immunohistochemical stains on cell block sections in both cases were positive for CK7 (Figures 4a and 4b), EMA and cytokeratin AE1/AE3. CD10 was focally positive. Vimentin and S100 were negative. TTF-1 and thyroglobulin were negative in the second case. Immunohistochemical studies were not done on the resected primary kidney tumour of these cases as morphologic features were classical of chromophobe renal cell carcinoma.

EM findings:

Electron microscopy on tissue sections showed focal intracytoplasmic microvesicles.

Cytogenetic analysis

FISH analysis on tissue from the nephrectomy specimens showed losses of chromosomes 1 (81%), 2 (74%), 6 (52%), 10 (81%), and 17 (74%) in the first case, and chromosomes 2 (86%), 6 (76%), 10 (98%), and 17 (86%) in the second case.

Discussion

ChRCC was first described by Thoenes et al. in 1985 (4). The tumour is characterised by large cells with abundant granular to fluffy cytoplasm with well-defined cell borders and perinuclear clearing (1-9) leading to confusion with clear cell carcinoma and oncocytoma. In difficult cases a positive Hale's colloidal iron stain (1-7, 9-12) and ultrastructural demonstration of numerous oval cytoplasmic microvesicles establishes the correct diagnosis of ChRCC. The characteristic cytomorphologic features noted correspond to the histologic features and include large polygonal to round cells with granular to flocculent cytoplasm, well defined cell borders, mild nuclear pleomorphism, vesicular nuclei, perinuclear clearing, and small to indistinct nucleoli. ChRCC has been shown to be immunoreactive for CK7 (1,2,5-8), cytokeratin AE1/AE3, EMA, and to be negative for vimentin (1,2,5,7 8) as seen in these two cases with positive Hale's colloidal iron stain and negative PAS and PAS-D stain. Ultrastructural study has demonstrated oval cytoplasmic microvesicles (1-4,7,9-11) which were focally seen on primary tumours in both cases. ChRCC shows loss of chromosomes 1, 2, 6, 10 ,13, 17 and 21 which may be used to confirm the diagnosis of ChRCC (10-12).

Despite the excellent prognosis associated with ChRCC, metastases may rarely develop, especially in large multifocal tumours. The presence of sarcomatoid elements, tumour size > 80 mm, tumour necrosis, and vascular invasion have been associated with poor prognosis (5,8). Invasion was present in the primary tumour of the second case. Although the cytologic features of ChRCC are unique, several tumours, such as renal oncocytoma, clear cell carcinoma, granular cell carcinoma, hepatocellular carcinoma, adrenal cortical carcinoma, lung carcinoma, and oncocytic tumours of salivary gland and thyroid must be considered in the differential diagnosis.

The presence of variegated cytoplasm and frequent perinuclear clearing in ChRCC and presence of uniform large cells with abundant homogeneous granular cytoplasm, lacking perinuclear clearing, and nuclear membrane irregularities, helps in distinction from renal oncocytoma (1,2,6,7,9,11,12).

In the current cases, characteristic morphologic features of ChRCC, diffuse strong positive CK7 ruled out the diagnosis of a renal oncocytoma. The absence of cytologic features of clear renal cell carcinoma, such as large clusters of cells with abundant clear to finely vacuolated or granular cytoplasm, many stripped nuclei, centrally located nuclei, prominent nucleoli, more uniform nuclear size, lacking perinuclear clear zone, and the positive CK7 in these cases and negative vimentin, excluded clear cell carcinoma. Hale's colloidal iron stain is negative in clear cell carcinoma. The distinction from granular cell variants of renal cell carcinoma may be made by the presence in the later of large cells with abundant granular cytoplasm, ill-defined cell borders, prominent nucleoli, and intermixed variable number of clear cells, negative Hale's colloidal iron stain, cytokeratin, EMA, and positive reactions for vimentin, S100 and CD68.

Metastatic ChRCC appears most commonly in the liver and lymph node, rarely at other sites, and must be distinguished from tumours of non-renal origin with superficial resembling features such as hepatocellular carcinoma, adrenal cortical carcinoma, lung carcinoma, and oncocytic tumours of salivary glands and thyroid. These possibilities were excluded as imaging of liver, pancreas, spleen, adrenals and lung was normal in both cases. TTF-1 and thyroglobulin were negative in the second case making origin from lung or thyroid unlikely.

Conclusions

Although the cytologic features of ChRCC have been previously described, there have been only a few reported cases of ChRCC diagnosed on FNA material (1 -3,7,9) and very few metastatic examples diagnosed using FNA (1-3,9). A correct diagnosis of ChRCC may be possible on cytomorphology along with a Hale's colloidal iron stain and confirmed by immunohistochemical and FISH analysis in difficult cases.

Acknowledgments

The authors acknowledge Robert Fauck for his contribution in Hale's colloidal iron staining, Richard Parfitt for his effort in FISH analysis, Louise Goossens for her photographic assistance, and Ian Tompson for graphical assistance.

References

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Author information

Sarla Naran, BSc CT(FIAC), Staff Cytotechnologist [1]

Sharda Lallu, BSc CT(FIAC), Staff Cytotechnologist [1]

Peter Bethwaite, MB ChB PhD FFSc(RCPA) FRCPA, Senior Lecturer [1,2]

[1] Department of Cytology, Anatomic Pathology, Wellington Hospital, Wellington

[2] Department of Pathology and Molecular Medicine, Otago University, Wellington

Corresponding author: Sarla Naran, Cytology Unit, Anatomic Pathology, Capital and Coast Health District Board, Wellington Hospital, Private Bag 7902, Wellington, New Zealand. E-mail: Sarla.Naran@ccdhb.org.nz
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Author:Naran, Sarla; Lallu, Sharda; Bethwaite, Peter
Publication:New Zealand Journal of Medical Laboratory Science
Article Type:Clinical report
Date:Aug 1, 2014
Words:2051
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