Gastrointestinal stromal tumor arising from anorectum: correlation of imprint cytology and radiologic imaging

The diagnosis of gastrointestinal stromal tumor (GIST) is generally established on histopathologic examination of surgical specimens. Gastrointestinal stromal tumor comprises a heterogenous group of neoplasms of the gastrointestinal tract previously referred to as leiomyomas, leiomyosarcomas, or schwannomas. Gastrointestinal stromal tumor arising from anorectum is a rare instance. We report a case of GIST for the correlation of imaging and cytologic features with immunocytochemical staining. A computed tomography and magnetic resonance imaging confirmed a 2-cm tumor growing into the rectal lumen. The central portion of the tumor showed T1-weighted imaging of low signal and suspected central necrosis by the T2-weighted imaging of high signal. Imprint cytology from excised tumors showed isolated or loosely aggregated spindle cells with scanty and fibrillary cytoplasmic processes, nuclear pleomorphism, fine granular chromatin, and irregular nuclear margins. Epithelioid tumor cells showed grooves with abundant cytoplasm and several round nucleoli. Both c-kit and CD34 antigen were positive with strong and diffuse stainability in smears as well as paraffin sections by immunoperoxidase staining. We suggest that the combined use of imaging diagnosis and cytology with immunocytochemical staining are useful initial diagnosis of GIST.

Spontaneous infarction of an intraductal papilloma of the breast: cytological presentation on fine needle aspiration

A relatively rare case of spontaneous infarction of an intraductal papilloma of the breast is presented which was considered to be suspicious for malignancy on fine needle aspiration (FNA) cytology. The aspirate revealed several groups of atypical cells featuring a high nuclear-cytoplasmic ratio, coarsely granular chromatin, and somewhat prominent nucleoli. There was abundant necrotic cellular debris in the background. These cellular features were considered evidence of ductal carcinoma of the breast. The correct diagnosis was made by open biopsy which revealed necrosis involving the breast due to infarction of an intraductal papilloma.

Langerhans cell histiocytosis of the skull on cytologic squash preparations

We present a case in which a primary cytodiagnosis of Langerhans cell histiocytosis (LCH) of the skull was made using squash preparations. The patient, a 25-year-old male, presented with raised intracranial pressure and decreased visual acuity. Magnetic resonance imaging revealed a large skull lesion with osteolytic features in the left frontal bone. The patient underwent surgical resection by the extended basal frontal epidural approach. The squash preparation smears were cellular and demonstrated a mixed population of small, mature lymphocytes, eosinophils, and a high histiocytes content. The histiocytes occurred as isolated or loosely cohesive and clustered. They possessed abundant cytoplasm with rounded cell shape and had characteristic nuclear features, composed of fine chromatin and delicate nuclear membranes. The cytologic features of these histiocytes were consistent with Langerhans cells (LCs). A final impression of LCH of the skull was rendered. Subsequent histopathology confirmed the diagnosis. LCs reacted with both S-100 protein and CD1a immunohistochemically. The demonstration of Birbeck granules on electron microscopic study was also noted. Whenever squash preparation yields a mixed population of mature lymphocytes, eosinophils, and histiocytes, the cytologists should be aware of and consider LCH as a diagnostic possibility.

Immunohistochemical expression of PTEN and beta-catenin for endometrial intraepithelial neoplasia in Japanese women

PTEN and beta-catenin are the most common genes for which genetic abnormalities are found in endometrioid adenocarcinoma (type I) and even in their precursors. Currently, the World Health Organization (WHO) classifies endometrial hyperplasia as a premalignant disease. However, one of the problems in the current WHO endometrial hyperplasia schema is that it is not always a reproducible classification system. Subsequently, the alternative molecular genetics and morphometric-based classification, referred to as the endometrial intraepithelial neoplasia (EIN) classification system, has been proposed. We reclassified endometrial lesions in Japanese women using the EIN category and compared them with the results of PTEN as well as beta-catenin immunohistochemistry. A total of 117 cases that were initially diagnosed as endometrial hyperplasia according to WHO classification were reevaluated histopathologically by the EIN diagnosis category. They were classified into 38 EIN and 32 benign architectural changes of unopposed estrogen (BAC), and 47 cases were excluded. In addition, for comparison, we examined 20 cases of normal proliferative endometrium (NPE). Subsequently, the expressions of PTEN and beta-catenin were analyzed immunohistochemically. Glandular epithelium was positive for PTEN in all the cases of NPE (20/20), whereas 12.5% (4/32) of BAC and 34.2% (13/38) of EIN were PTEN-null (negative). Endometrial intraepithelial neoplasia was significantly less frequently positive for PTEN than NPE (P < .025). The nuclear staining for beta-catenin was seen in 26.3% (10/38) of EIN cases, and the intensity was generally strong. Instead, none of the BAC or NPE showed positive nuclear staining. Thus, the nuclear staining was statistically more frequently seen in EIN than in the other 2 categories (P < .025 for each). In addition, 22 of 38 EIN cases (57.9%) were either PTEN-negative or nuclear beta-catenin-positive. This combination was statistically significantly more frequently seen than BAC (4/32, 12.5%) (P < .001) and NPE (0/20, 0%) (P < .0001). Immunohistochemical loss of PTEN and positive nuclear staining of beta-catenin were frequently seen in EIN but were not seen in NPE cases in Japanese women. The combination of PTEN-negative/beta-catenin-positive results may become the reliable marker for detecting EIN.

Myoepithelial cells in solid variant of intraductal papillary carcinoma of the breast: a potential diagnostic pitfall and a proposal of an immunohistochemical panel in the differential diagnosis with intraductal papilloma with usual ductal hyperplasia

We examined myoepithelial status in intraductal papillary carcinoma (IPC) along with the expression of high-molecular weight cytokeratin (HMWK) and neuroendocrine markers, with special reference to the differential diagnosis of solid intraductal papillary carcinoma(SIPC) and intraductal papilloma with usual ductal hyperplasia (IP-UDH). Twenty-six (93%) of the twenty-eight intraductal papillomas (IP) had myoepithelial cells in >70% of the epithelial-stromal interface of the intraluminal proliferating component. Six (29%) of twenty-one SIPC had almost complete myoepithelial layer like IP-UDH at the epithelial-stromal interface. HMWK (34 beta E-12) was diffusely positive in 14 (93%) of 15 IP-UDH, but 16 (76%) of 21 SIPC were completely negative for HMWK. Neuroendocrine markers were positive in 14 (67%) of SIPC, but all 28 IPs were completely negative. If only the presence of myoepithelial cells is emphasized as a benign hallmark, about 30% of SIPCs may be underdiagnosed as IP-UDH. However, by using a combination of myoepithelial markers, HMWK, and neuroendocrine markers, all of the 36 solid intraductal papillary lesions were properly classified as benign and malignant. Solid intraductal papillary lesions meeting at least two of the following criteria are highly likely to be malignant: (1) absence of myoepithelial cells(<10% of epithelial-stromal interface of intraluminal proliferating component), (2) negative HMWK(<10%), (3) positive neuroendocrine markers (>10%).

Metaplastic breast carcinoma with chondrosarcomatous differentiation: fine-needle aspiration cytology findings. A case report

Metaplastic carcinoma (carcinoma with pseudosarcomatous metaplasia) of the breast are high-grade carcinomas in which much of the tumor undergoes metaplastic change producing a pseudosarcomatous pattern. We report a case of metaplastic breast carcinoma (MBC) in whom fine-needle aspiration (FNA) cytology was performed with later histological confirmation. The lesion affected a 68-yr-old woman, with a tumor measuring 6.4 x 5.3 cm well demarcated mass located in the upper outer quadrant of the right breast. FNA cytology revealed a variety of markedly atypical cells, mainly spindle-shaped, and mitotic figures sporadically distributed against a severely necrotic background. Atypical chondrocytes were observed against a background of myxomatous substance that displayed metachromasia with May-Giemsa stain that resembled chondrosarcoma cells. Clusters of markedly atypical carcinoma cells that exhibited epithelial junctions were also seen, and immunostaining confirmed the presence of both mesenchyme-marker-positive sarcomatous and epithelial-marker-positive carcinoma cells. Careful attention to the precise cellular composition such as sarcomatous cells, chondrosarcomatous cells and carcinoma cells should allow the recognition of these neoplasms. Therefore, MBC seems to be very a characteristic tumor in which accurate cellular diagnosis may be achieved by FNA cytology.

Fine needle aspiration cytology: a survey of current European practice

Fine needle aspiration cytology (FNAC) is practised widely throughout Europe. The majority of countries have dedicated cytopathologists as well as histopathologists practicing cytology. Despite this, FNAC is performed mostly by clinicians and radiologists except in the larger centres with dedicated staff with a special interest in cytopathology. The advent of One-Stop diagnostic services and image-guided procedures are prompting further development of FNAC clinics where cytopathologists take their own samples, issue reports in the same clinical session and take extra material for ancillary tests to complete the diagnosis. The volume of FNAC work varies accordingly; in dedicated centres FNAC represents up to 80% of the workload whilst, in the majority of countries, it represents one quarter or less. Hence, the rate of inadequate FNAC varies widely, depending on the local sampling policies and the organ, but does not exceed 25% in any of the countries. The most sampled organs are breast and thyroid, followed by lymph nodes. Most countries have dedicated training in cytopathology for pathology trainees, the duration varying between 6 months and 2 years of the total training time. This discussion, focusing on European practices, highlights the heterogeneity of FNAC activity but also its success in many centres where it is practiced to a high standard, particularly in breast, thyroid and lymph node pathology. The relatively high rate of inadequate material in some centres reflects local policies and calls for greater uniformity of FNAC practice, particularly specimen sampling. To achieve this, the future direction should concentrate on specialist training, to include performing as well as interpreting FNAC, as part of the curriculum. Current emphasis on web-based training may not provide first hand experience of the FNAC procedure and should be supplemented by attending FNAC clinics and developing the technique to its full potential.

Direct intrauterine sampling with Uterobrush: cell preparation by the "flicked" method

The aim of this study was to evaluate the efficacy of endometrial cytology using the Uterobrush in the collection of samples for the diagnosis of endometrial lesions. The preparation technique for endometrial brushing specimens was also demonstrated. In their earlier study, the authors described the cyto-architectural criteria that appear to be more useful for the cytological assessment of endometrial lesions. Therefore, for the application of the diagnostic criteria, endometrial cytological sampling will become more important. With regard to the cell sample collection, the authors used the Uterobrush because the insertion into the uterine cavity is easy and painless. The authors compared the Uterobrush with the Endocyte, since they thought that cell clumps using the former device tended to be smaller. The purpose of the current study was to improve and evaluate cell preparation methods using the Uterobrush. The authors investigated three methods [i.e., conventional and improved techniques ("flicked" method) with the Uterobrush and the Endocyte] of endometrial cell collection and preparation. Using conventional methods, a brush was rolled along a glass slide and the collected material spread and smeared. However, using the "flicked" method, a brush is strongly flicked with forceps, so that the cells are transferred to the slide and its position is moved along the slide little by little and smeared. The frequency by size of cell clumps with tube or sheet-shaped pattern was examined in the preparations. Cell block specimens with the Uterobrush were also investigated. Endometrial cytology from a total of 90 women was evaluated. Most were outpatients and all were older than 20 yr (ranging from 20 to 54, average 42.7 yr). Of these, 30 cases from each group were examined by three methods. Uterobrush samples prepared by the "flicked" method have a greater quantity of cell clumps than those using the Endocyte sampler, while the frequency-by-size of cell clumps was by degree the same as the Endocyte. The cell clumps obtained in the Uterobrush "flicked" method preparation was considered equivalent or superior as an aid to making a diagnosis of endometrial lesions and it became obvious that the same criteria were applicable to both of instruments. Our cytological examination may be a potent aid to making a diagnosis of endometrial lesions and these findings will be helpful in the standardization of criteria in direct intrauterine cell samples.

Cellular features of endometrial hyperplasia and well differentiated adenocarcinoma using the Endocyte sampler

BACKGROUND

Because cellular atypia is often limited in endometrial hyperplasia and well-differentiated endometrial adenocarcinoma (WHO Grade 1 adenocarcinoma), diagnostic criteria for endometrial cytology have not been fully established. New diagnostic criteria based on the composition and architecture of tissue fragments (cytoarchitecture) in the smears were used in the present study. Cytologic features are of less importance because the distinction between endometrial hyperplasia and Grade 1 adenocarcinoma relies more on architectural features than cellular changes. Cell clumps of various size are usually collected abundantly with cytologic material using a disposable scraping device and it was noticed that those cell clumps reflected the histologic architecture. The purpose of the current study was to determine the form of the cytoarchitecture that reflects the histologic structure and to examine the cellular features in endometrial hyperplasia and Grade 1 adenocarcinoma.

METHODS

The frequency of each type of cell clump (tube or sheet-shaped pattern, dilated or branched pattern, irregular protrusion, and papillotubular pattern) were obtained from 49 cases of normal proliferative endometrium (NPE) (patient age range, 28-51 yrs; average age, 39.9 yrs), 63 cases of endometrial hyperplasia without atypia (EH) (patient age range, 35-65 yrs; average age, 47.7 yrs), 13 cases of endometrial hyperplasia with atypia (AEH) (patient age range 47-65 yrs; average age, 53.8 yrs), and 49 cases of Grade 1 adenocarcinoma (patient age range, 42-73 yrs; average age, 58.9 yrs).

RESULTS

Certain characteristics of the cytoarchitecture were observed. In the NPE, cell clumps with a tube or sheet-shaped pattern were found in 97.5% of cases. In the EH, cell clumps with a dilated or branched pattern were found in 34.9% of cases. In the Grade 1 adenocarcinoma, cell clumps with irregular protrusions were found in 61.8% cases, whereas a papillotubular pattern was present in 29.7% of cases.

CONCLUSIONS

The results of the current study revealed that cytoarchitectural criteria appear to be more useful for the cytologic assessment of endometrial lesions, especially for the diagnosis of endometrial hyperplasia and Grade 1 adenocarcinoma.

Cytologic diagnosis of brain metastasis from hepatocellular carcinoma by squash preparation

Hepatocellular carcinoma (HCC) metastasizes to the brain is rare instances. In published series and case reports of metastatic HCC, diagnosis of central nervous system metastases has been determined by histologic methods. We present a case of metastatic HCC of brain diagnosed by squash cytologic preparation. A 69-year-old male, HCV positive, suffering from post-hepatitic cirrhosis, initially diagnosed at age 68 with HCC presented with headaches of increasing frequency and severity. A computed tomography scan confirmed a 3-cm nodule in the right parietal lobe of the brain. Squash cytology was performed intraoperatively and preparations of a small tissue fragment resected from the mass showed medium-to-large-sized, well-cohesive clusters or sheets of uniform tumor cells. The tumor cells are highly cellular and contain solitary tumor cells in loose groupings as well as many fragments. They also appear somewhat bizarre and contain large, round, or ovoid nuclei with prominent nucleoli. Cytologic diagnosis of metastatic HCC was rendered reported and confirmed by a subsequent frozen section examination. To the best of our knowledge, this is the first reported case in which HCC was reported as brain metastasis, by using squash cytology. We suggest that intraoperative squash cytologic examination be viewed as a useful initial approach in the diagnosis of metastatic brain tumor.

Infarcted intraductal papilloma of the breast: Cytologic features with stage of infarction

Fine-needle aspiration cytology (FNAC) is being employed with increasing frequency for the pre-operative diagnostic workup of breast lesions. Although most cases show morphologic features very characteristic of specific entities, rare lesions with infarcted breast can cause problems in interpretation. We present cytologic findings in seven cases of an infarcted intraductal papilloma of the breast (IDPB) that was diagnosed by FNAC, and we also report the correlation of cytological features and stages of infarcted IDPB. In the early stage of infarction, numerous degenerative cells and necrotic debris were demonstrated. Isolated degenerative cells showed columnar, spindle, polygonal and fiber-like cells, with coagulated and smudged nuclei. Ghost cells were also seen. Extensive necrosis was demonstrated with a few sheets of ductal cells in the mid-stage of infarction. In the late stage of infarction, clusters of fibroblasts, ductal cells and necrotic debris were found. Knowledge of the characteristic cytologic pattern in different stages of infarcted IDPB may be helpful to suggest the probable pre-operative diagnosis of those lesions. Familiarity with this entity is important in preventing misdiagnosis of malignancy.

Endometrial glandular and stromal breakdown, part 1: Cytomorphological appearance

Endometrial carcinoma is the most common invasive neoplasm of the female reproductive tract. Early detection and accurate diagnosis of these lesions and its precursor by endometrial cytology is now accepted in Japan and regarded as an effective primary method of evaluating endometrial pathology (atypical hyperplasia or carcinoma). Careful cytomorphologic evaluation of the abnormal endometrial lesions has made possible an accurate and reproducible microscopic assessment. The current study was conducted to determine the significance of endometrial cytology on disordered endometrium associated with anovulation when compared with endometrial hyperplasia. From January 1998 through April 2004, 144 cases on which histopathological diagnoses were obtained by endometrial curettage after taken direct endometrial sample by Endocyte. The materials comprise 49 cases of normal proliferative endometrium, and 63 cases of endometrial hyperplasia without atypia were prepared as control cases. The cytomorphology was examined involving so-called endometrial glandular and stromal breakdown (EGBD). EGBD cases evidenced significant numbers of stromal cells condensed and formed compact nests with hyperchromatic nuclei and little or no cytoplasm. They were often associated with fragmented clusters of endometrial glands with condensed cluster of stromal cells. Both the fragmented cluster of endometrial glands and condensed cluster of stromal cells are a characteristic cytologic feature of EGBD endometrium on the cyto-architectural diagnosis. The combination of these cellular patterns is highly specific to this abnormal pathological condition in EGBD endometrium. To improve the accuracy of the cytodiagnosis, it is important that the cytology of the EGBD endometrium should be diagnosed negative; as a result, we can achieve successful endometrial cytology with cyto-architectural criteria for the endometrial pathology.

Endometrial glandular and stromal breakdown, part 2: Cytomorphology of papillary metaplastic changes

Careful cytomorphologic evaluation of abnormal endometrial lesions has made accurate and reproducible microscopic assessment possible. Histopathology of patients with dysfunctional uterine bleeding due to an anovulatory cycle usually contain endometrial glandular and stromal breakdown (EGBD) and papillary metaplasia on the endometrial surface epithelium, if an appropriate sample has been collected. We often recognized abnormal cell clumps in the cytological smears with EGBD cases. They were composed of metaplastic cells, and some irregular small projection figures were observed from the margins of the cell clumps. We describe the quantitation of metaplastic clumps with irregular protrusions (MCIP) in endometrial endocyte samples. The current study presents the cytomorphological characteristics of the metaplastic changes recognized in EGBD cases. During a 7-yr period, 144 cases for which histopathological diagnoses were obtained following endometrial curettage, after collecting a direct endometrial sample using the endocyte. The material comprised 49 cases of normal proliferative endometrium (NPE) (patients aged 28-51, average 39.9), 32 cases of EGBD (patients aged 30-67, average 49.6), and 63 cases of endometrial hyperplasia without atypia (EH) (patients aged 35-65, average 47.7). The following points were investigated: (1) the occurrence of metaplastic cells; (2) the occurrence and the frequency of MCIP; and (3) the occurrence of MCIP that contains condensed stromal clusters. Metaplastic cells were seen in 93.8% of the EGBD cases. Cytomorphologic pattern identified with MCIP was 90.6%, and its frequency showed 16.1%. The occurrence of MCIP that contain condensed stromal clusters (93.1%) showed a strong association in comparison with other lesions, such as NPE and EH. Our data appear to indicate that the appearance of MCIP with condensed stromal clusters originated from the papillary metaplasia, which occurred on the endometrial surface epithelium. The cytologic observation of those cells may be a useful indicator for providing the nature of EGBD endometrium.

Küttner's tumor of the submandibular glands: Report of five cases with fine-needle aspiration cytology

Küttner's tumor (KT) is a benign tumor-like lesion of the salivary gland that mimics neoplasm clinically because of presentation as a hard mass. Recently, the histomorphological and immunohistochemical findings of this lesion have been analyzed, and differential diagnostic problems relating to salivary gland lymphoma have been discussed. However, currently there is little information on the cytological findings of those lesions. We present cytological findings from five such cases using fine-needle aspiration cytology (FNAC). FNAC of this lesion may present a diagnostic challenge to the cytologist as lesions share some cytologic features with inflammatory process containing numerous lymphoid cells. Smears obtained from two cases contained moderate to large numbers of lymphoid cells without definite cytological atypia, scattered ductal structures, and acinar cell clusters. The remaining three cases showed low cellularity probably attributable to fibrosis that made it difficult to aspirate the cellular element. FNAC findings of scattered ductal structures surrounded by collagens and infiltrated by a mixed population of lymphoid cells, not specific for KT, are highly suggestive of the diagnosis with the appropriate clinical findings. However, a portion of cytological specimens of KT containing relatively large numbers of lymphoid cells should be differentiated from malignant lymphoma arising from the submandibular gland.

Eosinophilic cell change of the endometrium: a possible relationship to mucinous differentiation

Eosinophilic cell change is one of the most common endometrial metaplasias occurring in both non-neoplastic and neoplastic endometrium. Its phenotypic characteristics have not still been fully clarified. We examined expression of mucin core proteins in a total of 95 distinct histological areas of endometrial specimens comprising 39 benign nonhyperplastic endometria, 14 endometrial hyperplasias, and 42 endometrial carcinomas. Eosinophilic cell change was very common, seen in 27 endometrial areas (28%); mucinous metaplasia (28%) and ciliated (tubal) change (31%), were also frequently seen. Eosinophilic cell change was more frequently seen in endometrial hyperplasia and carcinoma than in benign nonhyperplastic endometrium. In endometrial carcinomas, eosinophilic cell change was frequently associated with mucinous metaplasia and the two types of metaplastic cells were occasionally intermingled in a single neoplastic gland. A total of 23 (85%) of 27 eosinophilic cell changes and 18 (72%) of 25 mucinous metaplasias showed MUC5AC expression. These frequencies of MUC5AC expression did not differ significantly among benign non-hyperplastic endometrium, endometrial hyperplasia and endometrial carcinoma. Totally, 15 (52%) of 29 ciliated (tubal) changes and two (100%) of two surface syncytial changes, which showed cytoplasmic eosinophilia at least focally, also expressed MUC5AC. Most of the endometrial changes characterized by cytoplasmic eosinophilia may be subtypes of immature mucinous metaplasia which express a mucin core protein but are not fully glycosylated.

Cytologic diagnosis of endosalpingiosis with pregnant women presenting in peritoneal fluid: a case report

The cytologic appearance of endosalpingiosis in peritoneal fluid cytology smears has not been extensively described. We report a case of endosalpingiosis in a 29-year-old pregnant female who presented with peritoneal fluid. Dense papillary epithelial clusters with indistinct ciliated cells were found in the Papanicolaou-stained smears. However, long and delicate cilia were obvious in papillary cluster with scanning electron microscopy. Cell nuclei were oval, with finely dispersed chromatin and uniform nuclear membrane. Peritoneal fluid cytology with these findings may be helpful to suggest the probable preoperative diagnosis of endosalpingiosis or benign glandular inclusions involving the pelvic peritoneum.

Papillary clusters as a diagnostic pitfall in urinary cytology of pseudosarcomatous fibromyxoid tumor of the bladder. A case report

BACKGROUND

Pseudosarcomatous fibromyxoid tumor (PFT) of the urinary bladder is an uncommon benign lesion that can involve any site in the bladder. Cellular features of PFT of the bladder are exceedingly rare. We describe the urinary cytology in a PFT patient who displayed numerous papillary fragments that suggested a malignant tumor.

CASE

A 52-year-old man was seen at the hospital for evaluation of gross hematuria. At cystoscopy, the urologist observed a 3-cm, smooth, polypoid and ulcerated mass extending from the trigone to the bladder neck. Urinary cytology showed many papillary clusters with irregular nuclear margins in the bloody cell background. No spindle cells were noted. Cytology was interpreted as papillary growth, factor transitional cell carcinoma, grade 2-3. A laparotomy with partial resection of the urinary bladder was carried out, and histologically the tumor was composed of spindle, stellate, fibroblastic cells embedded in myxoid stroma with little collagen. Immunohistochemical and ultrastructural studies revealed the fibroblastic nature of the lesion. The final diagnosis was PFT of the bladder on the basis of histologic examination of the resected material.

CONCLUSION

Papillary fragments are a diagnostic pitfall in urinary cytology of PFT lesions.

Highly anaplastic extraventricular ependymoma arising in an adult, mimicking metastatic adenocarcinoma with heavy stromal inflammation and emperiporesis

We report a case of extraventricular ependymoma arising in a 50-year-old woman that took an aggressive clinical course with recurrence three times. The initial tumor was a well-circumscribed nodule in the right temporal white matter measuring 2 cm in diameter. It showed variegated histological findings mimicking metastatic adenocarcinoma: an epithelioid arrangement of highly pleomorphic cells with pseudopapillary structures and perivascular pseudorosettes, and bizarre multinucleated giant cells with occasional emperiporesis surrounded by abundant mononuclear inflammatory cells, as well as a focal small area of conventional ependymoma. Emperiporesis and abundant mononuclear cell infiltration were not previously described in an ependymoma. The recurrent tumors predominantly showed an epithelioid pattern with frequent formation of astroblastoma-like pseudopapillary structures. Neoplastic cells were markedly atypical and had characteristic intracytoplasmic eosinophilic inclusion bodies. Much of the cells in both the initial and recurrent tumors showed a positive immunostaining for glial fibrillary acidic protein (GFAP) with accentuation to the cytoplasmic processes of the pseudorosettes and pseudopapillary structures. Epithelial membrane antigen (EMA) highlighted the epithelial differentiation of the tumor cells, while cytokeratin was completely negative. Although this tumor might be classified to at least WHO grade III from the histology and aggressive behavior, the exact grading is still controversial because of the rarity of such cases.