Primary sclerosing epithelioid fibrosarcoma of kidney with variant histomorphologic features: report of 2 cases and review of the literature

For immunohistochemical labeling, a polymer detection system (Leica, DS9800) and the BOND-MAX automated immunostainer was used. The standard antibodies consumed, vendors, and dilutions were summarized in Table 1.

FISH analysis was performed on representative 4–5 μm thick unstained formalin-fixed, paraffin-embedded tissue sections of the tumor samples of each case. For characterization of the possible underlying gene rearrangement or fusion gene events, the following FISH probe sets were utilized on both cases: Vysis LSI EWSR1 (22q12) and Vysis LSI FUS (16p11) Dual Color Break Apart Probes (Abbott Molecular, Inc., Des Plaines, IL) and EWSR1 and CREB3L1 spanning probe sets using cocktails of BAC clones (RP11-945 M21 and RP11-1126O13, and RP11-1014A16, RP11-1106 J11 and RP11-481I24 respectively) selected on the basis of their location per the UCSC Human Genome Browser [http://​genome.​ucsc.​edu/​cgi-bin/​hgGateway] and obtained from BAC/PAC Resources Center (Children’s Hospital Oakland Research Institute, Oakland, CA, USA).

Hybridization studies using the Vysis LSI Dual Color Break Apart Probes for the assessment of rearrangement of the FUS and EWSR1 loci were performed following the manufacturer’s instructions (Abbott Molecular, Inc., Des Plaines, IL). With respect to the custom spanning probes, each BAC clone was directly labeled by nick translation with either Spectrum Green- or Spectrum Orange-dUTP per the manufacturer’s protocol (Abbott Molecular, Inc., Des Plaines, IL). An amount of 3 ug of DNA for each probe or 1.5 ug for each of two probes were combined. All nick translation reagents were then multiplied by the total ug of DNA used in the cocktail. Amounts of 200 ng of each probe were hybridized to the target DNA and blocked with approximately 15 fold excess of a combination of Human Cot-I DNA (Invitrogen, Carlsbad, CA) and human placental DNA.

Prior to hybridization, the slides were pretreated at room temperature in 0.2 N HCl for 20 min, washed in water for 3 min, incubated at 80 °C for 25 min in VP 2000 Pretreatment Reagent (Abbott Molecular, Inc., Des Plaines, IL) and then washed again in water for 3 min. Subsequently, the slides were incubated for 15 min at 37 °C in protease solution [25 mg of protease in 50 ml of protease solution (Abbott Molecular, Inc., Des Plaines, IL), washed in 1 × PBS at room temperature for 5 min and then dehydrated in gradient ethanol (75, 85, and 100 %) at room temperature for 1 min each and air-dried. After the cells and probes were co-denatured at 80 °C for 10 min and incubated overnight at 37 °C using the HYBrite™ system (Abbott Molecular, Inc., Des Plaines, IL), post-hybridization washing was performed in 2 × SSC/0.1 % NP-40 at 72 °C for 2 min, followed by 2 × SSC/0.1 % NP-40 at room temperature for 1 min. The slides were then counterstained with DAPI II (Abbott Molecular, Inc., Des Plaines, IL). To confirm correct mapping, optimal signal strength, and lack of cross-hybridization, each probe set was also hybridized to metaphase cell preparations of karyotypically normal peripheral blood lymphocytes before proceeding with analysis of the patient samples.

The cutoff level for scoring a specimen as positive for a rearrangement of the FUS or EWSR1 locus or as positive for an EWSR1/CREB3L1 fusion was >15 % of the cells evaluated. Images were prepared using the Cytovision Image Analysis System (Applied Imaging, Santa Clara, CA). For each probe set, 100–200 interphase nuclei with strong and well-delineated signals were examined.

The patient was a 16-year-old girl who presented at the urology clinics with pain on the left side of the abdomen radiating to the back. Her past medical history was insignificant. Computerized axial tomography scans of the chest, abdomen, and pelvis revealed a 70 × 70 × 60 mm left renal mass (Fig. 1), bilateral pulmonary nodules (the largest being 16 mm in diameter), and widespread bone metastases in vertebrae, sacrum and left femoral head. A biopsy from the tumor in the kidney through laparotomy was performed followed by left radical nephrectomy after the diagnosis of malignancy.

Tumor occupied the entire upper half of the kidney, extended into the renal sinus, was a solid white unencapsulated lesion with sharp borders, measuring 7.5 × 7 × 7 cm in size (Fig. 2). Microscopical sections showed diffuse infiltration of the neoplastic tissue in kidney parenchyma separating normal renal elements from each other. The neoplastic cells were small, monotonous and epithelioid with clear to pale eosinophilic cytoplasm, and were arranged in single files, cords, nests or irregular aggregates in collagenous matrix (Fig. 3). Nuclei were generally round to oval, with indistinct nucleoli. Hypercellular areas alternated randomly with hypocellular densely hyalinized or at times myxoid stroma. Additionally, a peculiar lobular organization was noted in many regions where a renal tubule in the center was surrounded by concentric inner hypo and outer hypercellular zones of neoplastic cells (Fig. 4a and b). These lobules were separated from each other by myofibroblasts. Tubules entrapped in the tumor were lined by single layered Pax-8 positive cuboidal cells without atypia, some showed shallow papillary hyperplasia and rare mitosis. Mitotic rate was 1/10 hpf in the neoplasm and there were occasional areas of necrosis in the tumor. Hypercellular areas occasionally contained vague nodules of collagen mimicking those seen in hyalinizing spindle cell tumor with giant rosettes (HSCTGR). The surrounding kidney showed no specific pathologic changes. By immunohistochemistry, neoplastic cells were immunoreactive diffusely and strongly for vimentin, bcl-2 and CD99; EMA labelled them in a weak and patchy fashion (Fig. 5). They were negative for pan-cytokeratin, Pax-8, WT-1, CD34, S-100, GFAP, Melan-A, HMB-45, desmin, and estrogen and progesterone receptors. Smooth muscle actin (SMA) stained myofibroblastic cells in-between the neoplastic lobules (Fig. 6). INI-1 was preserved. Then, an immunohistochemical stain for MUC4 was performed which showed strong positivity throughout the tumor (Fig. 6). Finally, FISH analysis with the EWSR1 Break Apart probe revealed loss of one copy of the Spectrum Green labeled probe flanking the 3’ (telomeric) side of the EWSR1 gene as well as the presence of a single fused EWSR1/CREB3L1 signal (represented by a juxtaposed orange signal and green signal) consistent with the presence of an unbalanced der(22)t(11;22)(p11;q12) (Fig. 7), confirming the diagnosis of sclerosing epithelioid fibrosarcoma. FISH study was negative for a rearrangement of the FUS gene locus.

Patient was given chemotherapy with multiple agents. She is alive with disease after 30 month follow-up.

The patient was a 57-year-old woman who was investigated for cholelithiasis due to dyspeptic complaints. During abdominal ultrasonography, she was found to have a left renal mass incidentally. The CT scan showed that the tumor was located at the upper pole of the kidney and was measured 6 cm in the largest diameter. Her past medical history was unremarkable except for hypertension, congestive heart failure and arrhythmia. Serum and urine tests were within the normal limits. The patient subsequently underwent open left partial nephrectomy.

On gross examination, the specimen had an unencapsulated, solid - white firm tumor with irregular borders, measuring 7.5 × 5.5 × 4 cm (Fig. 8). Histologic examination revealed that tumor contained abundant entrapped native renal tubules throughout as in the first case, mimicking a biphasic neoplasm (Fig. 9). These tubules were hyperplastic and proliferating, were of various size and shapes, some being cystic or leaf-like, and lined by single layered cuboidal or occasionally flattened cells, all expressing nuclear Pax-8. Intraluminal papillary projections were common, but without cytologic atypia. Neoplastic component had a variable cellularity (Fig. 10). Hypocellular regions contained abundant hyalinized collagen and some showed myxoid change. Hypercellular areas were divided into anastomosing compartments by sclerotic collagen bands. Neoplastic cells were polygonal epithelioid or plump spindle type forming short fascicles (Fig. 11). Cytoplasm was clear or eosinophilic. Cellular pleomorphism was prominent with scattered bizarre and hyperchromatic nuclei, intranuclear inclusions were evident in some. Tumor abutted lining urothelium of renal pelvis without ulceration and formed large hypocellular sheets of short spindle cells in myxoid matrix encircling pelvic wall. There were rare foci of necrosis. Mitotic rate ranged 5–10/10 hpf. Immunohistochemical profile of tumor was similar to the first case including strong and diffuse MUC4, vimentin and bcl-2, weak EMA expression (Fig. 12) except negative immunoreactivity for CD99. SMA showed frequently scattered myofibroblasts between the tumor cells. FISH demonstrated an unbalanced der(22)t(11;22)(p11;q12), as in the case #1 (Fig. 13). A FUS gene rearrangement was not identified.

The lesion occupied both renal cortex and medulla, and invaded into peripelvic and perirenal fat tissue. As one of the surgical margins was in continuation with the tumor, the patient underwent left radical nephrectomy which showed 1 cm residual mass. No adjuvant treatment was given. Patient is alive without local or distant recurrence 10 months after surgery.