Histological Architectures Research Articles

The variable morphological spectrum of penile basaloid carcinomas: differential diagnosis, prognostic factors and outcome report in 27 cases classified as classic and mixed variants

BackgroundBasaloid carcinomas of the penis, HPV-related tumors, are morphologically less homogenous than originally thought. The study objective was to evaluate the prognostic influence of the basaloid pattern in mixed tumors.MethodsWe studied 154 Mexican patients from the Hospital de Oncología, CMN, Mexico City (2000–2013) and found 27 with basaloid features in at least 20% of the sections classified as classic basaloid (8 cases), warty-basaloid (7), papillary-basaloid (5) and usual-basaloid squamous cell carcinomas (7). We evaluated patients’ age, site and size of tumor, histological classification, grade, thickness, anatomical level, vascular and perineural invasion, prognostic index score and node involvement. Penile intraepithelial neoplasia in adjacent epithelia was documented. Follow up ranged from 12–78 months. Statistical methods were Fisher’s exact test and Kruskal-Wallis test. Kaplan-Meier method and log-rank test were used for survival analysis. The cutoff for statistical significance was p <0.05.ResultsThere were not clinical differences. Microscopically types were distinctive and easy to separate. Usual-basaloid squamous cell carcinomas were smaller, thinner and rarely invaded corpora cavernosa, with a low prognostic index score. Classic basaloid, warty-basaloid and papillary-basaloid carcinomas had higher rates of vascular and perineural invasion and higher prognostic index scores. These findings correlated with the rate of nodal metastasis. The majority of patients with classic and papillary-basaloid neoplasms died from systemic metastasis (87.5 and 80%) whereas only 1 patient with usual-basaloid carcinoma died of the disease (14%).ConclusionsBasaloid carcinomas are not a single entity but a spectrum of variable histological architectures mixed with those of classic basaloid tumors. Identification of mature squamous cells in a basaloid carcinoma may be important to recognize and report because patients with these tumors may carry a better prognosis.

Abstract LB-040: Establishment of a predictive patient-derived xenograft model for renal cell carcinoma

Abstract Renal Cell Carcinoma (RCC) is classically considered a difficult malignancy to diagnose and treat. Although the surgery is a resolving approach for many local tumors, the metastatic disease generally is characterized by poor outcomes. The lack of valid preclinical cancer models has hampered the discovery of valuable diagnostic, prognostic and predictive biomarkers to develop effective therapeutic options. In order to create preclinical models, we established an orthotopic patient derived xenograft (PDX) murine model using an enriched stem cell like-heterogeneous bulk obtained from surgery patients’ specimens. To predict effective conventional and innovative therapeutic treatment, the stem cell like-heterogeneous bulks were analyzed before injection for key total and phosphorylated protein expression by Reverse Phase Protein Array (RPPA). METHODS: Using specific enzymatic dissociation and culture conditions, we first isolated enriched stem cell like-heterogeneous bulks from fresh surgery specimens derived from 30 patients who underwent nephrectomy. After one week, bulks were orthotopically injected in immunocompromised mice (NSG mice). Cells were infected with lentiviral vector (Tween-Luc) and in vivo monitored by IVIS imaging system. The percentage of engrafting bulks, sizes and distal spreading capacity were evaluated. Several xenografts were further dissociated, serially inoculated and propagated for up to eighth generations. Bulks were analyzed before injection by RPPA. This technique performs the detection of total and phosphoproteins allowing the analysis of hundreds of proteins. This RPPA platform includes specific antibodies for key proteins belonging or involved in targeted therapy signaling cascade. RESULTS: Approximately 67% of the implanted samples engrafted. We observed a correlation between the engraftment success and the aggressiveness of the parental tumor. Moreover, the PDXs obtained from more aggressive tumors showed increased size. Hematoxylin and Eosin staining showed that PDX displayed similar histological architectures to parental tumors. Furthermore, immunohistochemical analysis demonstrated that PDX retained CD10 and PAX 8 expression, two typical RCC biomarkers, at similar level than parental tumors. Finally, we obtained maps highlighting the specific activated proteins which are key candidates of targeted therapy pathways by RPPA. CONCLUSIONS: Our established in vitro and PDX models recapitulate tumor histology and molecular characteristic creating new source for ameliorating diagnosis, prognosis and therapy sensitiveness prediction. Furthermore, we were able to propagate PDXs from the same patient for up to eight generations. Since in average tumor uptake is 4-5 weeks, it would be theoretically possible to test in parallel therapeutics in murine models while the corresponding metastatic patient is under therapy. The ability to generate large PDX animal cohorts is very promising and could be exploited to obtain valuable preclinical platforms for innovative drug testing. Moreover, the possibility to map a wide variety of intracellular pathways and biological functions in enriched stem cell like-heterogeneous bulks enable us to explore protein-protein interaction networks with potential impact on drug activity and to identify deregulated circuits related to pharmacological inhibition. Citation Format: Simona Di Martino, Gabriele De Luca, Ludovica Grassi, Giulia Federici, Laura De Salvo, Anna Laura Di Pace, Antonio Addario, Giovanni Muto, Manuela Costantini, Mauro Biffoni, Michele Signore, Steno Sentinelli, Michele Milella, Michele Gallucci, Désirée Bonci, Ruggero De Maria. Establishment of a predictive patient-derived xenograft model for renal cell carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-040.

An anaplastic lymphoma kinase-positive lung cancer microlesion: A case report

Anaplastic lymphoma kinase (ALK)-positive lung cancers are generally diagnosed at an advanced clinical stage. Herein, we report a case of an ALK-positive lung cancer patient who had a microlesion of this tumor type. The patient was a 51-year-old woman without a smoking history. Computed tomography performed during a lung cancer screening program showed a 7×5-mm subpleural nodule with an irregular border in the right lower lobe. The background lung parenchyma was almost normal. Serum tumor marker levels were not elevated. Histological assessment showed destructive growth in the center of the lesion, as confirmed using Victoria blue-hematoxylin and eosin staining and immunostaining for CD34 and D2-40; however, at the other site, the tumor mainly showed intra-alveolar growth with minor lepidic growth. The tumor cells were positive for thyroid transcription factor-1 and ALK. Fluorescent in situ hybridization of the tumor revealed an ALK gene spilt. Accordingly, the tumor was diagnosed as ALK-positive lung cancer. ALK-positive lung cancer presents diverse histological architectures in the early phase.

Histological architectures of clear cell carcinoma and their correlation to clinicopathologic features.

576 Background: The aim of this study is to clarify the relationship between histological architectures (HA) and clinicopathological features (CF) in clear cell carcinoma (CCC). Methods: Between 1984 and 2014 nephrectomy or partial nephrectomy were performed in 723 renal cell carcinoma cases in our hospital. Among them 603 cases (83.4%) were CCC. We reviewed the pathological reports and found 556 CCC cases had description of HA. The relationship between HA and CF were investigated. Results: HA were as follows: small acinar (SA)/acinar (A) in 453 cases (81.5%), large acinar (LA)/solid (S) in 113 (20.3%), papillary (P) in 54 (9.7%), Cystic (C) in 121 (21.8%) and tubular in 53 (9.5%). By the Spearman rank correlation, significant correlation was observed between HA and tumor grades: SA/A (rho -0.408, p &lt; 0.0001), LA/S (0.567, p &lt; 0.0001), P (0.257, p &lt; 0.0001), C (-0.241, p &lt; 0.0001). Acinar sizes were correlated with tumor grade (0.541, p &lt; 0.0001), tumor size (0.435, p &lt; 0.0001) and local stage (0.414, p &lt; 0.0001). LA/S or P showed low microvessel density evaluated by CD31 immunostaining, which resulted in weaker attenuation in corticomedullary phase of enhancement CT. On the contrary SA had high microvessel density and high attenuation after enhancement. Conclusions: HA is well-correlated with tumor grade, tumor size and local stage, and could be predicted by dynamic CT pattern preoperatively.

Ameliorative effect of propolis against cyclophosphamide-induced toxicity in mice

Context: Cyclophosphamide (CTX) is a common anticancer agent used for the treatment of several malignancies. However, upon treatment, it induces severe toxicity due to its oxidative stress capability. Propolis, a natural product collected by honey bees, has shown several biological activities, such as free radical scavenging and antioxidant agent.Objective: This study elucidates the protective effects of propolis against CTX-induced changes in mice.Materials and methods: Forty-eight male Swiss albino mice were divided into four groups; group 1 was intraperitoneally (i.p.) injected with 200 µL of phosphate buffer saline (PBS), group 2 was injected with 100 mg/kg/d propolis, group 3 was injected with a single dose of CTX (200 mg/kg), and group 4 was injected with a single dose of CTX (200 mg/kg) followed by propolis (100 mg/kg) for 7 consecutive days. After 12 d, mice were bled and then sacrificed to analyze the hematological, biochemical, and histological parameters.Results: The results indicated that CTX-injected mice showed an increase in the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, and creatinine and a decrease in the total number of white blood cells (WBCs) and platelets. Moreover, dramatically changes in the histological architectures of the liver and kidney were observed. The mice that were injected with CTX/propolis showed an improvement in the levels of ALT, AST, urea, creatinine, WBCs, and platelets. Moreover, the histological picture of the liver and kidney was significantly improved.Conclusions: In conclusion, propolis might be considered an effective agent in ameliorating the toxicity resulted from CTX treatment.

A comparative study of the histology and microanatomy of the stomach in Mystus vittatus (Bloch), Liza parsia (Hamilton) and Oreochromis mossambicus (Peters)

Histological and topological architectures in the mucosal epithelium of the stomach of Mystus vittatus, Liza parsia and Oreochromis mossambicus were studied. The mucosa of the sac like stomach of M. vittatus was made up of superficial epithelium and gastric epithelium. The superficial epithelium was made up of single layer of columnar epithelial cells while the gastric epithelium was composed of gastric glands. In L. parsia the mucosal epithelium of the gizzard like stomach consisted of single layer of columnar epithelial cells but gastric glands were totally absent. The caecal like stomach of O. mossambicus was made up of superficial columnar epithelial cells and tubular gastric glands. The topological characteristics of the entire mucosa of the stomach of M. vittatus, L. parsia and O. mossambicus were provided with mucosal folds forming empty concavities. However, the concavities were comparatively deeper in O. mossambicus. The mucosal surface of stomach also typified with columnar epithelial cells whose apical surfaces were provided with short and stubby microridges in M. vittatus and L. parsia while in O. mossambicus the microridges were fine and delicate. Physiological functions of the stomach of aforesaid fishes were discussed.

Hepatoprotective effect of vitamins C and E against gasoline vapor-induced liver injury in male rats

The protective effect of vitamins C and E against gasoline vapor-induced liver injury was investigated in rats. Liver injury was assessed from the activities of liver function diagnostic indices including serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma glutamyl transferase (\gamma-GT), alkaline phosphatase (ALP) activities, total serum protein (TSP), albumin concentrations, and the histological architectures of the liver tissues of the experimental animals. The results showed that gasoline vapors caused a significant (P = 0.05) higher than that of vitamin C. The results of our study suggest a protective effect of vitamin C and vitamin E against gasoline vapor-induced liver injury, with vitamin E as a better option.

TU‐G‐220‐04: High‐Frequency (HF), Three‐Dimensional (3D), Quantitative Ultrasound (QUS) for Detecting Metastases in Dissected Lymph Nodes

A reliable means of detecting metastases in lymph nodes is essential for accurate staging of cancer and effective planning of therapy. The standard means of detecting metastases in nodes is histopathologic evaluation of surgically dissected nodes; however, because examinations tend to be limited to thin sections derived from the center of the node, this time‐consuming procedure appears to have high false‐negative rates for metastases that are 2 mm or smaller. We have been investigating high‐frequency (HF) quantitative ultrasound (QUS) methods as a more‐effective means of providing a rapid and reliable detection of metastases in dissected nodes based on their ultrasound‐scattering properties.We acquired HF ultrasound and histological data from dissected lymph nodes of patients with colorectal, gastric, breast, and other cancers. Freshly dissected nodes were scanned in a saline bath using a raster pattern to acquire 3D RF echo‐signal data. Scans utilized a broadband, F‐2, 25.6‐MHz, single‐element transducer with scan vectors separated by 25 μm in X and Y directions. Scanned nodes were color inked to provide references for subsequent orientation, then fixed and serially‐sectioned in their entire volume at 50‐μm intervals. The presence of metastatic foci was determined histologically in every section; evaluation of node status in the center section provided a basis for comparison with conventional methods.To date, we have analyzed the echo signals of more than 240 nodes including abdominal nodes of colorectal and gastric cancer patients and axillary nodes of breast‐cancer patients. 3D images generated from RF data were segmented semi‐automatically to select nodal tissue for analysis. Echo signals from nodal tissue were processed to yield QUS estimates, which included spectral parameters, scatterer‐property estimates, and B‐mode envelope‐signal statistical features. Different histological node architectures were observed and different QUS results were obtained for abdominal compared to axillary nodes.Linear discriminant analysis and ROC‐curve methods were applied to assess the ability of QUS estimates to distinguish cancerous from non‐cancerous nodes. Classification performance was assessed for individual estimates and various linear combinations of estimates. ROC results for axillary as well as abdominal nodes showed excellent classification. For abdominal nodes, the best area under the ROC curve exceeded 0.95. For axillary nodes, the best area approached 0.90. Images based on QUS parameters showed an excellent ability to depict metastatic foci. Results to date strongly suggest that HF QUS methods may provide a clinically valuable means of detecting small metastatic cancers in dissected lymph nodes and significantly improving the sensitivity for metastases that might not be detected using current, standard histopathology procedures. The ability of HF QUS to reveal otherwise missed metastases will enable pathologists to more‐ efficiently focus histological effort on regions of nodes that have a high suspicion of containing cancer and minimizing wasted time evaluating actually cancer‐free nodes. Future studies will investigate the applicability of these methods to detection of nodal metastases in situ.

Comparative histological study of levels 1-3 supportive tissues using pelvic floor semiserial sections from elderly nulliparous and multiparous women

The connective tissue located between the uterine cervix and sacrospinous ligament (the uterospinous connective tissue; USCT) has recently been noted as the level 1 supportive tissue instead of the classical uterosacral ligament. We examined whether or not the USCT changes its histological architecture by vaginal delivery in correlation with the levels 2 and 3 supportive tissues. In the pelvic floors of 17 female cadavers (9 nuliparous and 8 multiparous), we compared histological architectures among the USCT, arcus tendineus fasciae pelvis (ATFP) and perineal membrane (PM). The USCT was evident as a string-like tissue structure in multiparous women or a thick mesh in nuliparous women. It consistently contained fewer elastic and smooth muscle fibers than other levels. In contrast, the ATFP usually contained abundant elastic fibers and smooth muscle. Likewise, the PM also displayed a constant morphology. Although all three sites were likely to be injured by delivery, the USCT seemed to be more severely damaged and/or more difficult to be recovered than the ATFP and PM.

Extraspinal ependymoma of the broad ligament

Extraspinal ependymoma is a rare tumor, occurring most commonly in the sacrococcygeal region, and only a small number of cases have been reported to arise in the uterine ligament. Herein is reported a case of extraspinal ependymoma arising in the broad ligament of a 27-year-old woman. The lesion was 14 cm in diameter with an intra-abdominal implant in the omentum. On cut section the tumor was found to be solid, and demonstrated hemorrhaging, necrosis, myxoid foci, and central cystic spaces. Microscopically the tumor was composed of a proliferation of short spindle or polygonal cells arranged in short fascicles or in a solid sheet-like fashion with occasional perivascular pseudorosettes, together with myxoid areas and variable histological architectures exhibiting cribriform, pseudopapillary, and variable-sized cystic patterns. On immunohistochemistry most tumor cells were positively reactive to glial fibrillary acidic protein (GFAP), CD99, estrogen receptor, and progesterone receptor. The patient has remained disease-free for 6 months after the adjuvant chemoradiotherapy. Extraspinal ependymoma should be considered as a differential diagnosis when examining unusual intrapelvic tumors, especially in young female patients. The identification of characteristic histological features such as perivascular pseudorosettes and immunohistochemical expression of GFAP are helpful for confirming the diagnosis.

Quantitative Histological Validation of Diffusion MRI Fiber Orientation Distributions in the Rat Brain

Diffusion MRI (dMRI) is widely used to measure microstructural features of brain white matter, but commonly used dMRI measures have limited capacity to resolve the orientation structure of complex fiber architectures. While several promising new approaches have been proposed, direct quantitative validation of these methods against relevant histological architectures remains missing. In this study, we quantitatively compare neuronal fiber orientation distributions (FODs) derived from ex vivo dMRI data against histological measurements of rat brain myeloarchitecture using manual recordings of individual myelin stained fiber orientations. We show that accurate FOD estimates can be obtained from dMRI data, even in regions with complex architectures of crossing fibers with an intrinsic orientation error of approximately 5–6 degrees in these regions. The reported findings have implications for both clinical and research studies based on dMRI FOD measures, and provide an important biological benchmark for improved FOD reconstruction and fiber tracking methods.

Immunolocalization of serum proteins in xenografted mouse model of human tumor cells by various cryotechniques

The transport mechanism of soluble molecules throughout the interstitial matrix is closely associated with human tumor behavior in vivo. However, the examination of soluble components in histological architectures has been hampered by artifacts caused during conventional tissue preparation. In this study, the immunodistribution of intrinsic and extrinsic serum components in tumor tissues was examined in xenografted human tumor cells using 'in vivo cryotechnique' (IVCT) and cryobiopsy, where target tissues are directly cryofixed in vivo. Human lung cancer cells were subcutaneously injected into the dorsal flank of nude mice, and paraffin sections and cryosections of produced tumors were prepared with different methods. Immunolocalization of serum proteins, including albumin, immunoglobulin G (IgG) and IgM, as well as intravenously injected bovine serum albumin (BSA) was examined. Their immunodistribution was more clearly observed in the interstitium by both IVCT and cryobiopsy than conventional methods. IgM was immunolocalized within blood vessels, whereas albumin and IgG were observed in the tumor interstitium. Moreover, intravenously injected bovine serum albumin exhibited leakage from the blood capillaries into surrounding connective tissues in 24 h, but it gradually diffused to the interstitium of the tumor masses during 3 days. These results suggest that molecular leakage from blood capillaries varies significantly in different areas of developing tumors, and that small serum proteins, but not large ones, were abundantly immunolocalized in the tumor interstitium. Both IVCT and cryobiopsy were found to be useful for immunohistochemical studies of soluble molecules in tumors with blood circulation, and may therefore be helpful for further histopathological analyses.

The effect of interaction of Rauwolfia vomitoria root bark extract with vitamin E on rats’ liver enzymes

In our previous paper we demonstrated the influence of Rauwolfia vomitoria root bark extract on cardiac enzymes of normal Wistar rats and the effectiveness of this root bark as a source of antihypertensive agent, as determined by the marker enzymes, would be a useful index for the toxicity of this plant in clinical application. In this paper we present the results of the effect of Rauwolfia vomitoria root bark extract and its interaction with vitamin E on the liver function enzymes, such as alkaline phosphatase (ALP), alanine amino transferase (ALT), aspartate amino transferase (AST), gamma glutamyl transferase (\gamma-GT), and the histological architectures of the liver tissues of normal animals. The results showed significant (P Keywords: Rauwolfia vomitoria, root bark, vitamin E, liver enzymes, histopathology

Secondary Lymphoid Areas in Calf Ileal Peyer's Patch

The secondary lymphoid tissues appear in sheep ileum after involution of ileal Peyer's patch (PP). However, the existence of the secondary lymphoid tissues before involution of ileal PP has not yet been studied. We examined morphological characteristics of the full length of calf ileal PP using gross and microscopic anatomical techniques. Most areas of ileal PP consisted of densely packed lymphatic follicles contained very few follicular T-cell and associated with only scant interfollicular areas. However, the proximal end of ileal PP consisted of widely dispersed lymphatic follicles contained many follicular T-cell and associated with large interfollicular areas. The histological architectures of the proximal end of ileal PP strongly resembled those of the secondary lymphoid tissue in calf.

The Influence of Cryopreservation on the Oligosaccharide Expression of Tooth Germ-Sugar Chain Expression of Frozen Tooth Germs-

To explore the influence of preservation by freezing on tissues of tooth germ, we examined changes in histological architectures and glycoconjugate expression detected by lectins, in tooth germs, with or without freezing, of postnatal 5 day rats. The results acquired were as follows: tissue architectures and cellular morphologies were similar between frozen and control groups. Stellate cells of enamel medulla and pulpal cells were, however, slightly atrophic at the control group. With lectin staining, there are no remarkable changes between frozen and control groups. From these results, we conclude that the influence of preservation by freezing was relatively small.

Three-dimensional observations of histological architectures: hepatic sinusoids and juxtaglomerular complex.

Computer aided three-dimensional (3D)reconstruction from serial sections is a useful technique to observe the spatial arrangement and relationship of histological structures. The present images have been reconstructed with a volume rendering method with Voxel View software(Vital Images, Inc.,USA). Using this method, we can obtain interesting 3D findings, which have not been confirmed with general microscopic observations.

Histological classification of renal cell carcinoma--problems in JUA classification

Although renal cell carcinoma (RCC) is often heterogeneous, the histological classification of RCC in Japanese Urological Association (JUA) is designed to select only the dominant histological components. We evaluated whether this system could provide an adequate information concerning the prognosis of the patients. Histological slides of 130 cases with RCC were microscopically evaluated. We classified these cases according to the JUA classification, and also checked the presence or absence of each histological components (3 cell types and 5 histological architectures) regardless of whether or not they were dominant. Univariate and multivariate analysis were then performed to determine the histological components which have prognostic impact on patient survival. Multivariate analysis demonstrated that only spinde/pleomorphic cells and solid architecture were the significant prognostic parameters. The presence of these histological components was not correctly shown in the JUA classification. The histological classification of RCC in JUA did not provide enough information about the presence of the important prognostic parameters. This system should be modified to describe all the histological components regardless of whether they are dominant or not.

Analysis of histological heterogeneity in renal cell carcinoma: tumor size-related histological change and its prognostic significance.

It is well recognized that the histology of renal cell carcinoma (RCC) is often heterogeneous. It is also believed that the prognosis of patients with large tumors is generally poorer than those with small tumors. However, there has been no detailed study on changes in histological features of RCCs associated with tumor growth. This study was conducted to investigate whether there are any specific histological changes related to tumor size and to study the prognostic value of histological parameters in RCCs. The presence or absence of each histological component (3 cell types and 5 histological architectures) was investigated in 110 RCCs. The tumor size-associated changes in the histological composition of the RCCs were evaluated, and the prognostic significance of the histological parameters was analyzed using univariate and multivariate analysis. The percentage of RCCs with multiple cell types increased with tumor size, whereas increases in multiplicity were not as prominent in the histological architectures. Several characteristic changes, however, were observed in both cell types and architectures. RCCs with a pure clear cell, pure alveolar pattern or cystic architectural pattern decreased, while those with granular or spindle/pleomorphic cell types, or papillary or solid architectural patterns increased with tumor size. A univariate analysis revealed that a clear cell type and an alveolar or cystic architectural pattern were associated with a better prognosis, while spindle/pleomorphic cells and a solid architecture pattern correlated with a poorer prognosis. Multivariate analysis of cell types and architectures showed, however, that only the presence of spindle/pleomorphic cell types and a solid architecture were independent prognostic variables. The histological composition of RCCs varied according to the size of the tumor. Sarcomatous components increased with tumor size and were independently associated with a poor prognosis. Further study is warranted to correlate specific genetic alterations with tumor growth-related histological changes in RCCs.

Morphology of diethylnitrosamine-induced lung tumours in Dzungarian dwarf hamsters

After transplacental application of 30 mg/kg b.w. diethylnitrosamine 16 out of 21 Dzungarian dwarf hamsters developed lung tumours. The histological picture of these tumours is described. The neoplasms are classified as papillary, tubular, or alveolar adenomas or adenocarcinomas, respectively. Different histological architectures occur in one and the same animal or even in different parts of the same tumour. The neoplasms derive from outgrowths of the epithelium of small bronchioles. The significance of the Dzungarian dwarf hamster as a suitable tool for transplacental and postnatal cancer research is discussed.

トリプシン処理腫瘍細胞の艀化鶏卵漿尿膜上培養に関する研究

Malignant tumor cells (HeLa strain, L strain, chicken sarcoma and human uterine cancer cells) were dispersed with trypsin and inoculated onto the chorioallantoic membrane (CAM) of embryonated chicken eggs. HeLa and L cells formed tumors on CAM. Some of factors affecting the tumor formation were age of eggs used and number of cells inoculated. In the present experiments, in which 9 to 13-day old eggs were used and each egg received 5-6×105 or more cells, the rate of tumor formation was practically 100%. The tumors became visible 3 or 4 days after the inoculation of cells and increased in size during the additional 3 to 5 days. The maximum size was about 15×15×5mm. The in vitro restoration or egg passage of the original cell strains was possible. While the tumors produced by either kind of cells were of the similar macroscopic appearance, their histological architectures were different. HeLa cells in the tumors were arranged in aciniform grouping, and the acini gathered together to form larger conglomerates. The L cell tumors were characterized by diffuse infiltration of round or a littleelongated cells without showing specific arrangement; this resembled the pattern of tumors produced by the chicken sarcoma cells which were more infiltrative and typically'sarcomatous.' Trypsinized cells from human uterine cancer tissues formed tumors when inoculated onto CAM. It was shown histologically that the tumors included acinous clusters of cells with undifferentiated characters; the type of cellulargrouping had a resemblance to the specific arrangement of HeLa cells, on one hand, and to that of the cells found in the original cancer tissues, on the other. Some concepts regarding growth of cancer cells are discussed, and a potentiality ofthe technique for studying cancer cells is suggested.