Fine-Needle Aspiration Cytology of Sarcomatoid Renal Cell Carcinoma: A Morphologic and lmmunocytochemical Study of 15 Cases Manon Auger, M.D., Ruth L. Katz, M.D., Avishay Sella, M.D., Nelson G. Ordbiiez, M.D., David D. Lawrence, M.D., and Jae Y. Ro, M.D.

Sarcomatoid renal cell carcinoma (SRCC), which accounts f o r 5 % ofall renal cell carcinomas (RCC), has a worse prognosis than conventional nonsarcomatoid RCC, making accurate diagnosis important. This study reports on the morphologic and im- munocytochemical features of I5 cases of SRCC (9 primary tu- mors and 6 metastases) diagnosed by fine-needle aspiration (FNA) biopsy. All but three cases showed a dimorphic cell population consisting of varying proportions of a high-grade epithelial compo- nent, either clear or granular-cell type and a spindle cell (sar- comatoid) component, of either jibrosarcomatous, malignant ji- brous histiocytoma (MFH), or unclasst3ed types. The sarcomatoid component in the biphasic and monophasic tumors stained posi- tively for cytokeratin in 12 of 14 (85%) cases, for vimentin in 10 oJ11 (91 %) cases, and for muscle-specific action in 4 of I 1 (36%) cuses. Of note, the three cases that demonstrated a purely sar- comatoid morphology stained positively for cytokeratin. Unlike in studies performed on surgically resected specimens, neither the proportion of the sarcomatoid component nor the presence of ne- crosis had prognostic signtj%ance, the discrepancy most likely being related to the sampling. We conclude that SRCC, both primary and metastatic, can be accurately diagnosed by FNA when cytologic features are evaluated in conjunction with im- munocytochemical jindings. Diagn Cytopathol 1993;9:46-5 1. XI 1993 Wiley-Liss, Inc.

Key Words: Renal cell carcinoma; Sarcomatoid; Fine-needle as- piration biopsy; Cytology; Immunocytochemistry

Sarcomatoid renal cell carcinoma (SRCC), first described in 1968, is an uncommon variant of renal cell carcinoma

Received February 3 , 1992. Accepted May 12, 1992. From the Departments of Pathology, Sections of Cytopathology

(M.A., R.L.K.) and Surgical Pathology (N.G.O., J.Y.R.), Medical On- cology (A.S.), and Diagnostic Radiology (D.D.L.), University of Texas M.D. Anderson Cancer Center, Houston, TX.

Address reprint requests to Dr. Ruth L. Katz, M.D. Anderson Cancer Center, Section of Cytopathology, 1515 Holcombe Blvd., Box 53, Hous- ton, TX 77030.

Dr. Auger is now at The Toronto Hospital, Toronto General Division, Department of Pathology, 200 Elizabeth St., Toronto, Ontario, Canada MSG 2C4.

(RCC), accounting for approximately 5% of all renal cell carcinomas.2 The need to recognize and correctly diag- nose this subtype of RCC relates to its poor prognosis, which has been shown to be worse than for conventional nonsarcomatoid RCC of similar clinical stage. Recogniz- ing SRCC is also important because of its propensity to manifest itself as a metastatic tumor with spindle cell morphology that can be confused with a variety of sar- comas. The morphological features of SRCC have rarely been reported in cytological material. 4,5 This paper sum- marizes our experience with 15 cases of SRCC diagnosed by fine-needle aspiration (FNA) biopsy.

Materials and Methods In a review of the M.D. Anderson Cancer Center pathol- ogy files from 1986 to 1991, 15 cases of SRCC were identi- fied out of 189 FNA of the kidney diagnosed as RCC, and 105 cytology consultations, which included both primary and metastatic sites. The FNAs in all cases were per- formed through 22-gauge needles under CT or fluoro- scopic guidance. The cases were included in this study if the smears exhibited either a dimorphic epithelial and spindle sarcomatoid cell population or a monomorphic spindle cell population that stained positively for cytoker- atin. The FNA material was obtained from the primary site in nine cases and from various metastatic sites in the remaining six cases. Smears were stained with Papanico- laou stain in all cases, and with Diff-Quik stain (Harleco, NJ) in some. Hematoxylin and eosin (H&E)-stained cell blocks prepared from the cytologic material were available in 11 cases.

The smears and cell blocks were evaluated for type and relative percentages of epithelial and sarcomatoid compo- nents as well as for necrosis. Immunocytochemical studies were performed using the avidin-biotin-peroxidase com- plex (ABC) method of Hsu et al. b on cytology smears or on formalin-fixed, paraffin-embedded sections from cell

46 Diagnostic Cytopathology, Vol 9, No 1 (9 I993 WIIXY-LISS. INC

FNA CYTOLOGY OF SARCOMATOID RENAL CELL CARCINOMA

blocks. Eleven of the 12 biphasic tumors and the three monophasic tumors had material on which at least one antibody could be tested. The primary antibodies used were a “cocktail” of three antikeratin mouse monoclonal antibodies (AE1 and AE3, Boehringer-Mannheim, In- dianapolis, IN, 1:200 dilution; and CAM 5.2, Becton Dic- kinson, Mountainview, CA, 1:5), which recognizes a wide range of high- and low-molecular-weight keratin peptides, vimentin (Dako Corporation, Santa Barbara, CA, 1:25); and HHF35 mouse monoclonal antibody to muscle-spe- cific actin (Enzo Biochem, New York, NY, 1:3,000). The specificity of the immunoreaction was verified by staining known positive and negative control tissue sections.

Formalin-fixed, paraffin-embedded surgical material was available in four cases. There was one nephrectomy specimen (case 14) and three surgical specimens were from metastatic sites, one each from the lung (case 8), pelvic soft tissue (case 10) and paraspinal soft tissue (case 15). Sections were stained with H&E and compared with the cytologic materials.

Statistical analysis correlating the presence of various cytologic features (percentage of sarcomatoid component and necrosis) with survival was performed using standard chi-square methods.

Results Clin ica 1 The patients were 8 men and 7 women ranging in age from 42 to 71 yr (mean, 58.7 yr; median 56 yr). All presented with clinical stage IV disease, one with stage IVa (due to local invasion into mesentery and colon) and 14 with stage IVb, according to Robson’s clinical staging. ’ The meta- static sites at presentation included: lungs (1 l cases), bone (5 cases), liver (4 cases), hilar lymph nodes (3 cases), retroperitoneal lymph nodes (3 cases), spleen ( 2 cases), adrenal gland (2 cases), brain (2 cases), pelvic soft tissue (1 case), pancreas (1 case), and paraspinal soft tissue (1 case).

R ad iologic Fin dings Renal angiographic studies were available in five cases. All of these tumors had some evidence of a mass effect either expanding or distorting the renal outline. Most of the tumors were large and bulky, measuring from 5 to 15 cm. All the lesions had increased irregular neovascularity pro- moting at least some degree of tumor blush and all exhib- ited a moderate to large increase in number of abnormal tumor vessels. Only one of the lesions had hypovascular areas, presumably due to either focal necrosis or to deriva- tion of extrinsic blood supply not opacified with contrast on the available angiogram. These findings were not spe- cific and can be seen in other types of nonsarcomatoid RCC.

Cytologic Findings In all but three cases, cytologic examination of the smears and/or cell blocks revealed a dimorphic cell population. One population consisted of the epithelial component, which was clearly characterized by individual or small clusters of round cells with moderate to abundant cyto- plasm, the latter being of the clear or granular type. The nuclei were usually round, had prominent nucleoli with nuclear membrane irregularity and were classified as nu- clear grade 4 as defined by Fuhrman’s nuclear grading criteria. *

The second cell population, which was seen in all cases, consisted of single spindle cells or, more commonly, of large clusters of spindle-shaped cells with elongated nuclei and little to moderate cytoplasm. In most cases, the chro- matin was fine, and prominent nucleoli were present in many cases. The degree of pleomorphism of the spindle- shaped cells varied but was most marked and associated with malignant giant cells in cases with an MFH-like sarcomatoid component (Figs. C- 1-C-3). In addition to this pattern, two others were recognized, primarily on cell blocks: a fibrosarcomatous pattern (Figs. C-4-C-8) char- acterized by spindle cells arrayed in fascicles and an un- classified sarcomatous-type pattern characterized by sheets of spindle cells not forming fascicles and not ad- mixed with malignant giant cells (Figs. C-9-C-12).

Table I summarizes the characteristics of the epithelial and sarcomatous components in each case along with clin- ical follow-up information. It can be seen from Table I that in 8 cases, more than 60% of the cell population on the smears was of the sarcomatoid type. Table I1 shows

Table I. Smears Combined with Clinical Data”

Breakdown of Epithelial and Sarcomatoid Components on

Epithelial Surcom u ioid

F/ U Case no. Type % Tumor Type % Tumor (mo)

components component

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15

Granular Granular Granular Granular Granular Clear Granular Granular Granular Clear Granular Granular

~

~

-

10 20 10 50 50 90 90 20 10 50 90 50 0 0 0

Fibros Fibros Unclass MFH Fibros Fibros Fibros MFH MFH Fibros Fibros Unclass Fibros MFH MFH

90 3D 80 2A 90 15A 50 5A 50 22A 10 4D 10 3D 80 3D 90 3D 50 27D 10 1A 50 4D

100 14A 100 6D 100 3.5D

“MFH, malignant fibrous histiocytomatous type; F/U, follow-up; D, dead; A, alive; Fibros, fibroaarcomatous type; Unclass, unclassified type; -, not present.

Diagnostic Cytopathology, Val 9, No I 47

Fig. C-1A

Fig. C-3

Fig. C-18 Fig. C-2

Fig. C-4

Fig. C-5 Fig. C-6

Figs. C-1-C-12. Figs. C-1-C-3. Sarcomatoid renal cell carcinoma, malignant fibrous histiocytoma-like type (case 8). C-IA, B: Aspiration cytology smear of the sarcomatoid component. Note the giant cell present with pleomorphic spindle cells (Papanicolaou, x 630). C-2: Histology of transbron- chial biopsy specimen of metastatic sarcomatoid renal cell carcinoma (H&E, ~ 4 0 0 ) . (2-3: Immunocytochemical stain showing strong positivity of the sarcomatoid tumor cells for keratin ( x 630). Fig. C-4-C-8. Sarcomatoid renal cell carcinoma, fibrosarcomatous type (case 1). C - 4 Aspiration cytology smear of the sarcomatoid component (Diff-Quik, x 630). C-5: Aspiration cytology smears of the sarcomatoid component (Papanicohou, X 630). C - 6 Aspiration cytology smears of the epithelial component (Papanicolaou, x 630). (2-7: Cell block made from cytologic material illustrating

Fig. C-I

Fig. C-9

Fig. C-8A

Fig. C-10

Fig. C-8B Fig. C-8C

Fig. C-11 Fig. C-12

sarcomatoid component (H&E, X 630). C-8: Immunocytochemical stains performed on the cell block. Note the positivity of the spindle cells for keratin (A), for vimentin (B) and focally for muscle-specific actin (C) ( X 630). Figs. C-9-C-12. Sarcomatoid renal cell carcinoma, unclassified type (case 12). C - 9 Aspiration cytology smear of the epithelial component (Papanicolaou, x 400). C-10: Aspiration cytology smear of the sarcomatoid component (Diff-Quik, X400). C-11: Aspiration cytology smear of the sarcomatoid component (Papanicolaou stain X400). C-12: Cell block made from the cytologic material (H&E x 630).

AUGER ET AL.

Table 11. Clinical Follow-up*

Proportion of Sarcomatoid Component vs.

- No. of' patients

o/c Sarcomatoid component in tumors Alive Dead

> 60% 3 5 < 60% 3 4

*P:>o.Io. -

the distribution of cases according to whether the sar- comatoid component made up more or less than 60% of the total tumor and to clinical outcome. There was no statistically significant correlation between survival and the proportion of the sarcomatoid component (P > 0.10).

Necrosis was present in 5 cases and absent in 10. Six of 10 patients without tumor necrosis and 3 of 5 patients with necrosis died of tumor. There was no statistically signifi- cant correlation between presence or absence of necrosis and survival (P > 0.10). The diagnoses made by FNA were confirmed by histologic examination of the cell blocks in 1 I cases and by histology of surgical material in 4 cases.

Immunocytochemical Findings The epithelial component recognized on the smears in all 1 I biphasic tumors showed diffuse strong positivity for keratin. The sarcomatoid component of the biphasic and monophasic tumors stained positively for keratin in 12 of 14 cases (85%), for vimentin in 10 of 11 cases (91%), and for muscle-specific actin in 4 of 11 cases (36%). The im- munocytochemical staining reactions of the sarcomatoid component are summarized in Table 111. Figures 1C and 2E illustrate immunocytochemical results in two cases.

Follow- Up Nine patients have died of their disease with survival times ranging from 3 to 27 mo (median, 3.5 mo). Six patients were alive at the last follow-up, with survival ranging from 1 to 22 mo (median, 14 mo).

Discussion SRCC is an uncommon renal tumor accounting for ap- proximately 5% of all RCC. For a tumor to be diagnosed as SRCC, it must consist of a typical RCC component associated with a definite sarcomatoid component. The two components may abut directly upon or intermingle with each other.9

Very little has been written about the cytological fea- tures of this entity.4,5 The report by Hidvegi et a1.5 is based on FNA performed on surgically resected SRCC specimens. Up to now, no clear cytologic diagnostic crite- ria have been defined for this entity. Our experience with the FNA cytology in 15 cases of SRCC shows that, in most instances, the criterion (i.e., a dimorphic population

Table 111. Immunocytochemical Findings in Sarcomatoid Components"

Case Muscle Sarcomatous n 0. Keratin Vimentin actin type

Biphasic tumors

1 + + Focal + Fibros 3 + 4 - + - MFH 5 + Focal + N/A Fibros 6 + Focal + - Fibros 7 + N/A - Fibros 8 Focal + - - MFH 9 + + Focal + MFH

10 Focal + Focal + - Fibros 11 + + - Fibros 12 - N/A N/A Unclass

Focal + ~ Unclass

Monophasic tumors

13 + Focal + Focal + Fibros 14 + + Focal + MFH 15 Focal + N/A N/A MFH

a + , positive staining in majority of cells; Focal +, positive staining in minority of cells; -, absence of staining; Fibros, fibrosarcomatous type; MFH, malignant fibrous histiocytomatous type; N/A, not available; Unclass, unclassified type.

of epithelial and spindle-shaped cells) applied to surgical specimens can also be used for cytologic specimens.

The proportions of the epithelial and sarcomatoid com- ponents seen on the smears from the dimorphic tumors in our series (12 of 15) varied widely. Some tumors exhibited approximately equal amount of epithelial and sarcomat- oid components, while in others either the epithelial or sarcomatoid component predominated.

In occasional cases (three in our series), the smears exhibited a monophasic pattern consisting exclusively of the sarcomatoid component, with no obvious epithelial component. However, in all three cases, the sarcomatoid component stained positively for keratin. This is in keep- ing with reports of others' who have shown that the spin- dle cells of the sarcomatoid component react for keratin and present ultrastructural features of epithelial differen- tiation. This combination of cytological and immunocyto- chemical features makes it possible to diagnose SRCC in its primary or metastatic sites, even in cases having an exclusively monomorphic spindle cell component. The positivity for keratin in such cases helps distinguish the tumors from true sarcomas in most cases, although it is reported in the literature that some sarcomas, such as leiomyosarcoma lo and endometrial stromal sarcomas, '' can coexpress cytokeratin. It is thus conceivable that some of our monomorphic cases could be true sarcomas with keratin expression rather than SRCC. However, the oc- currence of the monophasic spindle cell pattern on FNA is uncommon, and furthermore, since SRCC are much

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FNA CYTOLOGY OF SARCOMATOID RENAL CELL CARCINOMA

more frequent than true renal sarcomas, such a pattern is much more likely to represent the former rather than the latter statistically. The focal positivity for muscle actin in four of our cases most likely reflects myofibroblastic dif- ferentiation rather than true muscle differentiation. ’’

It should be noted that the preparation of cell blocks from the cytologic material may be of great benefit, espe- cially in equivocal cases. I t is often easier to appreciate the presence of an epithelial component on cell blocks than on smears alone. In addition, the evaluation of tissue sections from cell blocks makes it easier to assess the sarcomatoid component, and the blocks provide a good source of mate- rial for immunocytochemical evaluation.

SRCC is known to be a highly aggressive malignancy with a dismal prognosis, even worse than that of con- ventional nonsarcomatoid RCC of similar stages. Ro et al., in their histologic study of 42 cases, reported that in addition to tumor stage, the presence of tumor necrosis in the sarcomatoid area and the proportion of tumor com- posed of the sarcomatoid component were two other im- portant prognostic factors, the latter being an independent variable for stages I and TI. The overall prognosis in our series was poor and did not appear to be influenced by the presence of necrosis or the proportion of the sarcomatoid component. The discrepancy between the findings of Ro et al. and our study might be related to the fact that the sample obtained by FNA is much smaller than were the surgical materials they examined.

The ability to accurately diagnose SRCC by FNA has a significant impact on patient care. Many patients re- ferred to our institution with high-stage (stage IV) renal neoplasms are often treated with systemic therapy solely on the basis of diagnoses of their renal masses made by FNA, obviating the need for nephrectomy. Other patients are treated on the basis of F N A diagnoses of their metas- tases in the presence of a renal mass. Recognition of this subtype of RCC has implications for prognosis and possi- bly for treatment.3 This report shows that an accurate

diagnosis of SRCC by FNA cytology is possible, especially when both smears and cell blocks are assessed in conjunc- tion with immunocytochemical analysis.

Acknowledgments The authors wish to thank Ms. Hazel Dalton and Mr. Thomas Brooks for their technical assistance in im- munocytochemistry .

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