Rhabdoid Phenotype Research Articles

Cecal Adenocarcinoma With Prominent Rhabdoid Feature: Report of a Case With Immunohistochemical, Ultrastructural, and Molecular Analyses

Colorectal adenocarcinoma with rhabdoid phenotype is extremely rare, and only 1 case of adenocarcinoma showing rhabdoid dedifferentiation has been reported. The authors present another case of cecal adenocarcinoma with prominent rhabdoid feature in a 66-year-old man. The 13-cm sized tumor consisted mainly of rhabdoid cells and partly of adenocarcinoma, and transition from adenocarcinoma to rhabdoid areas was noted. Ultrastructural analysis revealed intracytoplasmic aggregates of intermediate filaments in the rhabdoid cells. Adenocarcinoma cells were diffusely immunoreactive to cytokeratin 7 and AE1/3, but occasionally positive for vimentin. The rhabdoid cells were negative for cytokeratin 7, weakly/focally immunoreactive to AE1/3, and diffusely positive for vimentin. These results suggested that the rhabdoid cells were dedifferentiated adenocarcinoma. Analysis of the rhabdoid cells with molecular techniques is also presented.

MP-16.14: Rhabdoid phenotype renal cell carcinomas: clinicopathologic, immunohistochemical, and flow cytometry study

MP-16.14: Rhabdoid phenotype renal cell carcinomas: clinicopathologic, immunohistochemical, and flow cytometry study

Primary pleural epithelioid hemangioendothelioma with rhabdoid phenotype: Report and review of the literature

Epithelioid hemangioendothelioma (EHE) is a rare malignant vascular tumor described in diverse locations including lung and liver. Relative to these sites, primary EHE of the serous cavities is uncommon. EHE in the serous cavities mimics mesothelioma and adenocarcinoma clinically, radiographically, cytologically, and histologically. EHEs have plasmacytoid epithelioid cells with cytoplasmic vacuoles. In addition to these features, we noted eccentric nuclei with abundant eosinophilic cytoplasm and nuclei displaced peripherally by globular cytoplasmic inclusions imparting a "rhabdoid" phenotype. These cells were often seen surrounding a hyaline core. Rhabdoid features are not unique to a single entity, and a comprehensive immunohistochemical panel is essential. We report the occurrence of pleural EHE with rhabdoid features presenting in a pleural effusion, and review the literature of primary serosal EHEs.

Poorly differentiated thyroid carcinoma with rhabdoid phenotype: A diagnostic dilemma—Report of a rare case

Rhabdoid tumor is a distinct entity reported in renal and extrarenal sites. Malignant tumors of various types may have rhabdoid phenotype. There are eight case reports of carcinomas of thyroid with rhabdoid phenotype. All of these cases, except two, have been reported in middle-aged women (42-72 yr) and have had an aggressive clinical course with death occurring within few months to 4 yr after diagnosis. We report a case of poorly differentiated carcinoma of the thyroid with rhabdoid phenotype in a 22-yr-old male. The rhabdoid cells were immunopositive for thyroid transcription factor-1, vimentin, epithelial membrane antigen, and focally for cytokeratin. Synaptophysin, chromogranin, thyroglobulin, carcinoembryonic antigen, smooth muscle actin, myogenin, and desmin were all negative. To the best of our knowledge this is the ninth case report of carcinoma of the thyroid with rhabdoid phenotype. This case, unlike the previous reported cases, has certain unusual features including presentation in a young male, the absence of either follicular/papillary differentiation, and immunohistochemical profile of the rhabdoid cells.

Immunohistochemical Analysis of INI1 Protein in Malignant Pediatric CNS Tumors: Lack of INI1 in Atypical Teratoid/Rhabdoid Tumors and in a Fraction of Primitive Neuroectodermal Tumors without Rhabdoid Phenotype

Immunohistochemical lack of nuclear INI1 protein expression has been recently described as characteristic finding in atypical teratoid/rhabdoid tumors (AT/RTs), and has been suggested as useful marker to distinguish AT/RTs from other malignant pediatric central nervous system (CNS) tumors. In this study, we examined a large series of malignant pediatric CNS tumors to determine the immunohistochemical expression of INI1 protein in different malignant pediatric tumor entities. Archival paraffin-embedded biopsy specimens of 289 malignant pediatric CNS tumors including medulloblastomas, supratentorial primitive neuroectodermal tumors, glioblastomas, anaplastic astrocytomas, anaplastic ependymomas, choroid plexus carcinomas, germ cell tumors, and AT/RTs were analyzed immunohistochemically for expression of nuclear INI1 protein. Positive INI1 staining was observed in 263 tumors. Lack of INI1 protein was detectable in 26 tumors. Seventeen of the 26 tumors showed morphologically characteristic features of AT/RTs, whereas 9 embryonal tumors did not display rhabdoid features. Tumors without rhabdoid phenotype but lack of INI1 showed an aggressive clinical course and poor response to conventional treatment regimens. In summary, immunohistochemical expression of INI1 protein is lacking in tumors displaying characteristic morphologic features of AT/RT. Furthermore, a certain number of embryonal tumors without rhabdoid features but lack of INI1 protein and aggressive biologic behavior can be detected. We conclude that INI1 protein analysis should be routinely performed in all malignant pediatric embryonal CNS tumors to detect cases with lack of INI1 protein, because patients with these tumors are likely to benefit from intensified treatment.

Adrenocortical adenoma with rhabdoid features

We report a case of an aldosterone producing adrenocortical adenoma with rhabdoid features in a 16-year-old girl. Grossly, the tumor measured 30 mm in diameter and weighed 24 g. Histologically, the tumor was composed of approximately equal parts of tumor cells with rhabdoid features arranged in a solid and trabecular pattern and cells characterized by compact eosinophilic cytoplasm, solid growth with focal necroses, and increased mitotic activity. The lipid-rich tumor cells with ample clear vacuolized cytoplasm represent a minor component. Immunohistochemically, all the tumor cells showed the same results and were positive for vimentin, synaptophysin, Melan A, and α-inhibin. Cytokeratin CAM 5.2 was positive only focally. Chromogranin A, actin, α-actin, S100 protein, EMA, and cytokeratin AE1/AE3 were negative. Rhabdoid features have been described in many tumors of variable histogenesis; however, to the best of our knowledge, the presence of rhabdoid phenotype has never been described in either adrenocortical adenoma or carcinoma.

Intracytoplasmic Inclusions (Including the So-Called "Rhabdoid" Phenotype) in Pancreatic Endocrine Tumors

The cytoplasm of pancreatic endocrine tumors (PET) can show a diverse range of appearances from clear, to oncocytic, to intracellular mucin accumulation, and the presence of intracytoplasmic inclusions. Intracytoplasmic eosinophilic inclusions can vary morphologically and the spectrum ranges from small, dot-like hyaline inclusions, to deeply acidophilic/eosinophilic ones that occupy almost the whole cytoplasm and displace the nucleus eccentrically: the so-called "rhabdoid" phenotype. The aim of this study was to analyze the frequency, morphology, behavior, and relationship to clinicopathological features of large intracytoplasmic inclusions, including the rhabdoid phenotype, in a large number of PET. The morphological features of 84 cases were assessed for the presence of large, globular intracytoplasmic inclusions. Fourteen of 84 cases contained intracytoplasmic inclusions with 5 cases containing cells conforming to the characteristic rhabdoid morphology. The remaining nine cases showed pale intracytoplasmic inclusions. Four of the five cases with rhabdoid cells had spread to lymph nodes and/or peripancreatic fatty tissue. This study confirms that a spectrum of large intracytoplasmic inclusions is encountered in PET, ranging from lightly eosinophilic intracytoplasmic globules to the more typical rhabdoid phenotype (deeply eosinophilic inclusions). This phenotype, in particular the rhabdoid cells, is worthy of attention as a proportion may show lymphovascular invasion with evidence of metastasis at the time of presentation, irrespective of size, mitotic rates, or necrosis.

Papillary thyroid carcinoma with anaplastic transformation showing a rhabdoid phenotype solely in the cervical lymph node metastasis

We describe a rare case of anaplastically transformed papillary thyroid carcinoma with a rhabdoid phenotype appearing solely in a metastatic focus. A 77-year-old man presented with a rapidly enlarging, painful right lateral cervical mass. CT scan revealed a tumor in the right upper pole of the thyroid gland and a right lateral cervical mass. Examination of surgically resected specimens disclosed that the thyroid tumor was a well-differentiated papillary carcinoma (2.0 cm in diameter), and the right lateral cervical mass was an anaplastic carcinoma (2.4 cm in diameter) showing a rhabdoid phenotype with scant amounts of a papillary carcinoma component in the periphery, considered to be transformed through the metastasis of the papillary thyroid carcinoma in a cervical lymph node. The rhabdoid cells had eccentric nuclei with conspicuous nucleoli and spherical hyaline cytoplasmic inclusions, which are immunoreactive for vimentin and sarcomeric actin. Ultrastructurally, these had globular aggregation of thin and intermediate filaments. Nuclear immunoreactivity for INI1 indicated that the tumor had no INI1 abnormalities, suggesting a secondary rhabdoid tumor. Recurrence developed in the right cervical and mediastinal lymph nodes, and the patient died of disease 6 months after surgery. A rhabdoid phenotype is a pathological hallmark indicating the aggressive nature not only in the neck region, but also in other organs.

Cutaneous extrarenal rhabdoid tumor with myogenic differentiation

The rhabdoid phenotype is characterized by large epithelioid cells with abundant eosinophilic cytoplasm and paranuclear inclusions of intermediate filaments. Although originally described in tumors from pediatric kidneys, the rhabdoid phenotype has since been described in a variety of patient ages and extrarenal sites. Extraordinarily, the rhabdoid phenotype has emerged in cutaneous neoplasms, either as a pure extrarenal rhabdoid tumor or a composite phenotype coupled with another malignancy. Regardless of the clinical setting, the rhabdoid phenotype is uniformly associated with aggressive biological behavior. We report the findings from a rare and very aggressive primary extrarenal rhabdoid tumor of the skin with myogenic differentiation. A 53-year-old woman presented with an ulcerated nodule on her right medial calf and ipsilateral inguinal lymphadenopathy. Histological examination of the skin nodule as well as cytologic examination of a lymph node disclosed the characteristic rhabdoid phenotype. Electron microscopy demonstrated paranuclear globules of intermediate filaments; special stains suggested an underlying myogenic histogenesis. The patient was aggressively treated with chemotherapy but ultimately died of her disease 8 months after presentation. The rhabdoid phenotype is rarely seen in cutaneous neoplasms, but when present, portends a poor prognosis adding particular importance to its recognition.

Intrathoracic rhabdoid carcinoma: a clinicopathological, immunohistochemical, and ultrastructural study of 6 cases

We evaluated the clinicopathological spectrum of intrathoracic rhabdoid carcinoma, including its immunophenotype and ultrastructural features. Our series included 6 cases arising from the lung (4 cases) and the anterior mediastinum (2 cases). The patients were 4 men and 1 woman aged between 40 and 63 years (median, 53 years). Microscopically, all of the lesions were composed of loosely cohesive, large, atypical polygonal cells, with glassy cytoplasms and eccentric nuclei. Chromatin texture was finely granular or open. On immunohistochemical stain, the neoplastic cells were positive for vimentin in all cases, positive for vimentin, keratins and/or epithelial membrane antigen in all cases, and negative for other antigens. In 1 case, neoplastic cells were also positive for CD34. Electron microscopic study showed prominent perinuclear whorls of densely packed intermediate filaments or mitochondria. All patients were treated with combined chemotherapy and radiotherapy. One patient died 8 months after the diagnosis was made. Of the remaining patients, 3 are alive with evidence of disease progression, including brain metastases. We concluded that rhabdoid neoplasms arising in the thoracic cavity are aggressive tumors of epithelial lineage and should be categorized as true "rhabdoid carcinomas" instead of being ambiguously designated as "intrathoracic rhabdoid tumors" or "carcinomas with rhabdoid phenotype."

Proximal-Type Epithelioid Sarcoma: Report of Two Cases in the Perineum

The authors report two cases of perineal proximal-type epithelioid sarcoma in middle-aged men, age 51 and 43 years old. Both tumors were located in the right side. In the first patient a 7.5-cm, well-encapsulated tumor was completely excised. The second patient was a referral case with incomplete excision, but the computed tomography scan and magnetic resonance imaging showed a 14-cm nonencapsulated tumor involving the soft tissues of the inner thigh and perineum, as well as metastasis in right inguinal and retroperitoneal lymph nodes. Both neoplasms had a predominant solid pattern alternating with occasional discohesive areas. Both were composed of large oval to polygonal cells with vesicular nuclei, conspicuous nucleoli, and amphophilic to eosinophilic cytoplasm. Rhabdoid phenotype was identified in the second case only. The first neoplasm displayed 15% necrosis, 7 mitoses per 10 high-power field, focal vascular invasion, and no extracapsular invasion. The other exhibited 60% necrosis, 12 mitoses per 10 high-power fields, extensive vascular invasion, no distinct capsule, and invasion of the surrounding fatty tissue. Both were positive for vimentin, cytokeratin, epithelial membrane antigen, and CD34. Muscle-specific actin was negative in the first case and focally positive in the second. CD56 was positive in the second case and negative in the first case. Desmin, CD45, CD30, factor VIII, CD31, S100, HMB45, calretinin, and synaptophysin were negative in both. Since proximal-type epithelioid sarcoma can be confused with a number of other soft tissue tumors with epithelioid and/or rhabdoid features, the authors emphasize the immunohistochemical differential diagnosis.

Pulmonary large cell carcinoma with rhabdoid phenotype

Large cell carcinoma of the lung with a rhabdoid phenotype is very rare. We present a 55-year-old man with multiple nodules in his lung. He had an emergency operation because of abundant hemoptysis. The microscopic appearance was a large cell carcinoma with a pure rhabdoid phenotype. There were no foci of any other carcinomatous components. Tumor cells had abundant eosinophilic cytoplasmic globules and eccentric nuclei and did not adhere to each other. Histochemically, these cells were periodic acid-Schiff-negative. Immunohistochemically, vimentin and neuron-specific enolase were positive. Epithelial membrane antigen was focally and weakly positive, p53 was positive in 60% of tumoral cells, and Ki-67 (MIB-1 labeling index) was 50%. The patient died of disseminated disease 2 months after the operation.

Esophageal carcinoma with a rhabdoid phenotype: A case report of diagnosis by endoscopic ultrasound-guided fine-needle aspiration

Malignant extra renal tumors with rhabdoid phenotype are aggressive neoplasms associated with a poor prognosis. These tumors have been reported in soft tissue and various organs including the gastrointestinal tract. We report one of such tumors arising in the esophagus and discuss the cytopathologic, immunohistochemical, and ultrastructural features. Endoscopic ultrasound-guided fine-needle aspiration (FNA) cytology revealed a highly cellular tumor, consisting of polygonal poorly cohesive cells with prominent eosinophilic paranuclear cytoplasmic inclusions. Immunohistochemical staining showed strong cytoplasmic positivity for vimentin and cytokeratin. Electron microscopy revealed presence of numerous intermediate filaments. To the best of our knowledge, this is the first example of carcinoma with rhabdoid phenotype of the esophagus diagnosed by FNA cytology.

JUNE 2004: A MALE IN HIS LATE 60s WITH RECURRENT EXTRA‐CEREBRAL TUMOR

June 2004: Over the past year, this man in late-60s had complained about progressive weakness of concentration and memory disturbances, associated with word finding difficulties. MRI examination revealed an extra-axial, parasagittal tumor 3 cm in diameter located in the left frontoparietal region. Five years ago, a meningioma in the same region, with radiographic appearance comparable to the present tumor had been totally removed. The histological picture of the current tumor was dominated by sheets of large rounded pleomorphic tumor cells with abundant eosinophilic cytoplasm and eccentric nuclei (rhabdoid cells). Cytoplasmic inclusions were frequent; occasionally,multinucleatedtumorcellswereseen. Mitoticfigures were absent and the MIB was 3%. Meningothelial lobules were scarce, and regions with fibroblastic appearance were absent. There were no psammoma bodies, necrosis or brain invasion. Moderate immunoreactivity for EMA was found. Additionally, strong cytoplasmic immunoreaction for vimentin within the rhabdoid cells was observed. Review of the previous material showed small islets of rhabdoid cells. Rhabdoid meningioma is an uncommon meningioma variant. It has been suggested that rhabdoid meningiomas are highly aggressive tumors (WHO grade III)and that the rhabdoid phenotype represents a marker of malignant transformation in meningiomas. Histologically, rhabdoid meningiomas usually exhibit signs of anaplasia, a high mitotic activity, and a markedly increased MIB-1 labeling index. Extracranial metastases may occur in the course of the disease. However, not all rhabdoid tumors appear to have anaplastic features (as this case illustrates). Another interesting feature of rhabdoid meningiomas is that in a significant number of cases, the rhabdoid cells appear only at the time of recurrence. Alternatively, as seen in this case, the rhabdoid cells may be already present in the primary meningioma, but not as the predominating histological feature.

Pulmonary Large Cell Carcinoma with Rhabdoid Phenotype

A 70-year-old woman presented with a coin lesion in her left lung. The tumor was well circumscribed and had a large area of central necrosis with a thin rim of viable tumor cells. It showed a solid growth pattern of polygonal cells with eosinophilic intracytoplasmic inclusion bodies. Immunohistochemically, the tumor cells were positive for vimentin, neural cell adhesion molecule, neuron-specific enolase, and vascular endothelial growth factor. Electron microscopy revealed intracytoplasmic inclusion bodies consisting of whorled intermediate filaments. Based on histological and immunohistochemical findings, the patient was diagnosed as having pulmonary large cell carcinoma with rhabdoid phenotype (LCCRP). The patient was in stage IA, and the histological findings may be the prototype of pure LCCRP. The tumor recurred after 6 years, and the second tumor had more apparent intracytoplasmic inclusion bodies. It is worthwhile detecting and recognizing the significance of these intracytoplasmic inclusions because of the poor prognosis of this tumor.

Adult Rhabdoid Renal Cell Carcinoma Divergent Differentiation of Conventional (Clear Cell) Carcinoma

c Background.—Pediatric rhabdoid tumor of the kidney is regarded as a distinct neoplasm, whereas rhabdoid differentiation in adult renal cell carcinoma is usually found in association with conventional (clear cell) tumor, from which it is thought to evolve. Objective.—To further characterize the rhabdoid phenotype in adult renal cell carcinoma and to determine its origin by genetic analysis. Design.—We performed histologic, immunophenotypic, and genetic analyses on 5 cases of adult renal cell carcinoma with rhabdoid differentiation, 3 samples of adjacent conventional (clear cell) tumor, and 6 conventional (clear cell) control tumors. Results.—Rhabdoid tumors differed from conventional (clear cell) carcinoma as follows: (1) macroscopically, rhabdoid tumors were solid white uniform masses; (2) microscopically, they had large rhabdoid cells with abundant eosinophilic cytoplasm, reduced lipid content, and the absence of a branching vascular pattern; and (3) biologically, they had a high metastatic potential. Despite these differences, loss of chromosome 3p in both the rhabdoid and clear cell carcinoma samples from 1 patient suggested a clonal origin. An identical mutation of the VHL gene in both rhabdoid and clear cell tumor samples from 2 patients confirmed a clonal origin for the histologically distinct tumor types in those cases. Conclusion.—Adult rhabdoid renal cell carcinoma can in some cases arise from conventional (clear cell) renal carcinoma and should be considered a clinically important form of renal cell carcinoma separate from, but analogous to, sarcomatoid change. (Arch Pathol Lab Med. 2002;126:1506‐1510)

Adult rhabdoid renal cell carcinoma.

Pediatric rhabdoid tumor of the kidney is regarded as a distinct neoplasm, whereas rhabdoid differentiation in adult renal cell carcinoma is usually found in association with conventional (clear cell) tumor, from which it is thought to evolve. To further characterize the rhabdoid phenotype in adult renal cell carcinoma and to determine its origin by genetic analysis. We performed histologic, immunophenotypic, and genetic analyses on 5 cases of adult renal cell carcinoma with rhabdoid differentiation, 3 samples of adjacent conventional (clear cell) tumor, and 6 conventional (clear cell) control tumors. Rhabdoid tumors differed from conventional (clear cell) carcinoma as follows: (1) macroscopically, rhabdoid tumors were solid white uniform masses; (2) microscopically, they had large rhabdoid cells with abundant eosinophilic cytoplasm, reduced lipid content, and the absence of a branching vascular pattern; and (3) biologically, they had a high metastatic potential. Despite these differences, loss of chromosome 3p in both the rhabdoid and clear cell carcinoma samples from 1 patient suggested a clonal origin. An identical mutation of the VHL gene in both rhabdoid and clear cell tumor samples from 2 patients confirmed a clonal origin for the histologically distinct tumor types in those cases. Adult rhabdoid renal cell carcinoma can in some cases arise from conventional (clear cell) renal carcinoma and should be considered a clinically important form of renal cell carcinoma separate from, but analogous to, sarcomatoid change.

Choroid plexus carcinomas and rhabdoid tumors: phenotypic and genotypic overlap.

Five of six poorly differentiated choroid plexus carcinomas identified at our institution contained cells displaying a rhabdoid phenotype. Immunoperoxidase stains showed focal positivity for cytokeratin, epithelial membrane antigen, glial fibrillary acidic protein, S100, and vimentin. The MIB-1 proliferative index ranged from 7.0% to 27.1%. All six tumors were p53 positive. Only the one child with Li-Fraumeni syndrome had a p53 germline mutation. Electron microscopy verified choroid plexus differentiation and the co-existence of rhabdoid cells. Of the five studied, four had deletions of chromosome 22 [three with monosomy 22 and one with del(22)(q12)]. Thus, there was a phenotypic and genotypic overlap between choroid plexus carcinomas and rhabdoid tumors.

Proximal-Type Epithelioid Sarcoma: A Clinicopathologic Study of 20 Cases

We studied the clinicopathologic and immunohistochemical features of 20 cases of proximal-type epithelioid sarcoma to identify prognostic factors. The 20 patients ranged in age from 13 to 80 years (mean, 40 y); 12 patients were male and 8 were female. The tumors presented as deep soft-tissue or subcutaneous masses on the inguinal region in five, the thigh in four, the vulva in three, the axilla in three, and one each in the flank, chest wall, back, hip and perineum. The tumors ranged from 2 to 16 cm at their greatest diameter (mean: 7.8 cm). Histologically, 12 tumors (60%) were classified as the large-cell subtype, characterized by sheets of large cells with prominent nucleoli resembling poorly differentiated carcinoma, and a frequent rhabdoid phenotype, six (30%) were classified as the conventional subtype, and two (10%) as the angiomatoid subtype. The numbers of tumors exhibiting immunoreactivity for various markers were: vimentin (20 cytokeratin (20 [100%]); epithelial membrane antigen (17 [85%]); CD34 (9 [45%]); CD99 (5 [25%]); muscle markers, either desmin or α-smooth muscle actin (3 [15%]), other markers such as S-100 protein, neurofilament, neuron-specific enolase, synaptophysin and CD56 (12 [60%]); and p53 (16 [80%]). Fourteen lesions (70%) exhibited an MIB-1 index of 30% or more and, by a system of histologic grading using the MIB-1 score, 16 tumors (80%) were classified as high-grade (Grade 3). Thirteen patients (65%) developed local recurrence and 15 (75%) had metastases, primarily to the lymph nodes. At the last follow-up, 13 patients (65%) had died of their disease. A large tumor size and early metastasis were independently associated with a poor outcome. We conclude that proximal-type epithelioid sarcomas are rare, undifferentiated soft-tissue sarcomas of adults, with epithelioid features and a frequent rhabdoid phenotype. These tumors, when arising in proximal locations, have a much worse prognosis than those arising in distal locations.

Lung carcinoma with rhabdoid cells: a clinicopathological study and survival analysis of 14 cases.

We determined the clinicopathological features of primary lung carcinomas with rhabdoid cells by defining the immunophenotype of rhabdoid cells and analysing survival. Rhabdoid cells are distinctive in having an eccentric nucleus and a large intracytoplasmic inclusion on routinely stained sections. Based on the number of rhabdoid cells, 45 cases of large cell carcinoma were divided into the following three types: lung tumour with a rhabdoid phenotype (LTRP) (n=4), lung carcinoma with a small number of rhabdoid cells (LCSR) (n=10), large cell carcinoma containing no rhabdoid cells (LCNR) (n=31). LTRP is composed of at least 10% rhabdoid cells. In LCSR the percentage of rhabdoid cells is less than 10%. LTRP and LCSR are associated with locally advanced disease. Immunohistochemical stains were positive for epithelial markers in all LTRP and eight LCSR, for neuroendocrine markers in one LTRP and three LCSR. The outcome is worse for patients with LTRP than LCSR or LCNR. LCSR shows a trend close to LCNR. Stage-matched survival analysis, however, revealed no statistically significant difference among the histological subtypes. Rhabdoid cells are heterogeneous except for epithelial markers and vimentin positivity. Less than 5% of rhabdoid cells has a negligible effect on prognosis.