S100A8 and S100A9 are associated with endometrial shedding during menstruation.

Matrix metalloproteinases (MMPs) and their major source, endometrial stromal cells (ESCs), play important roles in menstruation. However, other mechanisms in endometrial shedding may be unexplored. This study focused on four proteins: S100A8 and S100A9 (alarmins) are binding partners and induce MMPs, MMP-3 cycle-dependently plays a key role in the proteolytic cascade, and CD147, which has S100A9 as its ligand, induces MMPs. Immunostaining for these proteins was performed on 118 resected specimens. The percentage and location of each positive reaction in ESCs were measured and compared using Image J. The influence of leukocytes on S100A8 or S100A9 immunopositivity was also examined. From the premenstrual phase, S100A8 and MMP-3 began to have overlapping expressions in ESCs of the superficial layer, and ESC detachment was found within these sites. S100A9 was expressed from the late secretory phase and CD147 already from earlier. Later, the expression sites of S100A9 and CD147 included those of S100A8. Before menstruation, S100A8 or S100A9 expression was not affected by leukocytes. These results suggest that the local formation of S100A8/S100A9 complex, which occurs specifically in ESCs upon progesterone withdrawal, induces the local expression of MMP-3 and serves as a switch to the lysis phase.

A Case of Neonate with Split Cord Malformation Presenting with Hypoplasia of the Left Lower Extremity.

The frequency of split cord malformation (SCM) is approximately 1 in 5000 births; however, patients are rarely diagnosed with SCM in the neonatal period. Moreover, there have been no reports of SCM with hypoplasia of the lower extremities at birth. A 3-day-old girl was transferred to our hospital for a thorough examination of hypoplasia of the left lower extremity and lumbosacral abnormalities detected after birth. The spinal magnetic resonance imaging (MRI) revealed a split spinal cord in a single dural tube. Based on the MRI findings, the patient was diagnosed with SCM type II. Following discussions with the parents, pediatricians, neurosurgeons, psychologists, and social workers, we decided to perform untethering to prevent further neurological impairment after achieving a sufficient body weight. The patient was discharged on day 25 of life. Early diagnosis and intervention may improve the neurological prognosis in terms of motor function, bladder and bowel function, and superficial sensation; thus, clinicians should report infrequent findings that may lead to SCM diagnosis. SCM should be differentiated in patients with left-right differences in the appearance of the lower extremity, particularly in those with lumbosacral abnormalities.

Membranous S100A10 involvement in the tumor budding of colorectal cancer during oncogenesis: report of two cases with immunohistochemical analysis.

BACKGROUND: Tumor budding (TB) and poorly differentiated clusters (PDCs) are a sequence of histologic findings that predict worse prognosis and node metastasis in colorectal cancer (CRC). TB and PDC (TB/PDC) are caused by cancer cell detachment and are distinguished by the number of cancer cells that constitute a cell cluster. In short, PDC is regarded as the previous step of TB. TB/PDC and epithelial-mesenchymal transition (EMT) are closely linked, but its pathogenic mechanisms are still unclear. S100A10, a member of the S100 protein family, forms a heterocomplex with annexin A2 (ANX A2) and then translocates to cell membrane from the cytoplasm and plays various roles in cell dynamics, including plasminogen activation. S100A10 is the activation modulator of the heterocomplex and promotes cell invasion. S100A10 is involved in the remodeling of both actin and extracellular matrix (ECM), which is also associated with EMT. CASE PRESENTATION: In two representative cases of conventional advanced CRC, we immunohistochemically examined S100A10 and ANX A2 expressions in which both TB and PDC were prominent. Both CRCs metastasized to multiple regional lymph nodes. In both cases, a membranous positivity for S100A10 was diffusely found in both tumor buds and PDCs and was observed in the tumor cells protruding toward the stroma, giving rise to TB/PDC. However, even in tumor glands with TB/PDC, the tumor cells with a smooth border around the stroma showed either cytoplasmic fine-granular expression or no positivity. The immunoreactivity for ANX A2 was almost the same as that for S100A10. In the main tumor components without TB/PDC, no distinct positivity was detected at their smooth borders. CONCLUSIONS: During oncogenesis, membranous S100A10 has the potential to be related to TB of CRC. This may be due to plasminogen activation, actin remodeling, and interaction with an altered ECM. However, further study is required to confirm this hypothesis.

Membranous overexpression of S100A10 is associated with a high-grade cellular status of breast carcinoma.

S100A10 promotes tumor invasion in various cancers. Although genetic studies on S100A10 in breast carcinoma (BC) have been used for molecular biological classification, immunohistochemical studies are lacking. We aimed to identify the correlation between S100A10 expression in BC and various pathological parameters, including morphological features to determine histological grade (HG). Immunostained serial paraffin-embedded tissue sections from 176 cases of resected BC or normal mammary ducts (controls) were assessed for the membrane expression of S100A10. Of the 176 cases, 125 conventional infiltrating ductal carcinomas were chosen, comprising 67 (53.6%) S100A10-positive tumors, whereas normal mammary ducts were S100A10-negative. S100A10 immunoreactivity in ductal carcinoma in situ (n = 51) was similar to that of invasive carcinoma. The distinct membrane-immunopositivity was correlated with high HG, severe nuclear pleomorphism, frequent mitotic counts, high Ki-67 labeling index, HER2/neu overexpression, and low estrogen receptor status (P < 0.05), but not with tubular formation, pT categories, node metastasis, vessel permeation, and pStage. Membrane overexpression of S100A10 in BC correlates with the high-grade morphological and molecular status of the carcinoma cell rather than stromal invasion and architectural deviation. Evidence points to the use of S100A10 as a biomarker representing a high-grade cellular status of BC.

Bcl11b SWI/SNF-complex subunit modulates intestinal adenoma and regeneration after γ-irradiation through Wnt/ß-catenin pathway.

SWI/SNF chromatin remodeling complexes constitute a highly related family of multi-subunit complexes to modulate transcription, and SWI/SNF subunit genes are collectively mutated in 20% of all human cancers. Bcl11b is a SWI/SNF subunit and acts as a haploinsufficient tumor suppressor in leukemia/lymphomas. Here, we show expression of Bcl11b in intestinal crypt cells and promotion of intestinal tumorigenesis by Bcl11b attenuation in Apc (min/+) mice. Of importance, mutations or allelic loss of BCL11B was detected in one-third of human colon cancers. We also show that attenuated Bcl11b activity in the crypt base columnar (CBC) cells expressing the Lgr5 stem cell marker enhanced regeneration of intestinal epithelial cells after the radiation-induced injury. Interestingly, BCL11B introduction in human cell lines downregulated transcription of ß-catenin target genes, whereas Bcl11b attenuation in Lgr5(+) CBCs increased expression of ß-catenin targets including c-Myc and cyclin D1. Together, our results argue that Bcl11b impairment promotes tumor development in mouse and human intestine at least in part through deregulation of ß-catenin pathway.

A low-pungency S3212 genotype of Capsicum frutescens caused by a mutation in the putative aminotransferase (p-AMT) gene.

The purpose of this study was to identify the genetic mechanism underlying capsinoid biosynthesis in S3212, a low-pungency genotype of Capsicum frutescens. Screening of C. frutescens accessions for capsaicinoid and capsiate contents by high-performance liquid chromatography revealed that low-pungency S3212 contained high levels of capsiate but no capsaicin. Comparison of DNA coding sequences of pungent (T1 and Bird Eye) and low-pungency (S3212) genotypes uncovered a significant 12-bp deletion mutation in exon 7 of the p-AMT gene of S3212. In addition, p-AMT gene transcript levels in placental tissue were positively correlated with the degree of pungency. S3212, the low-pungency genotype, exhibited no significant p-AMT transcript levels, whereas T1, one of the pungent genotypes, displayed high transcript levels of this gene. We therefore conclude that the deletion mutation in the p-AMT gene is related to the loss of pungency in placental tissue and has given rise to the low-pungency S3212 C. frutescens genotype. C. frutescens S3212 represents a good natural source of capsinoids. Finally, our basic characterization of the uncovered p-AMT gene mutation should contribute to future studies of capsinoid biosynthesis in Capsicum.

Simple and rapid synthesis of magnetite/hydroxyapatite composites for hyperthermia treatments via a mechanochemical route.

This paper presents a simple method for the rapid synthesis of magnetite/hydroxyapatite composite particles. In this method, superparamagnetic magnetite nanoparticles are first synthesized by coprecipitation using ferrous chloride and ferric chloride. Immediately following the synthesis, carbonate-substituted (B-type) hydroxyapatite particles are mechanochemically synthesized by wet milling dicalcium phosphate dihydrate and calcium carbonate in a dispersed suspension of magnetite nanoparticles, during which the magnetite nanoparticles are incorporated into the hydroxyapatite matrix. We observed that the resultant magnetite/hydroxyapatite composites possessed a homogeneous dispersion of magnetite nanoparticles, characterized by an absence of large aggregates. When this material was subjected to an alternating magnetic field, the heat generated increased with increasing magnetite concentration. For a magnetite concentration of 30 mass%, a temperature increase greater than 20 K was achieved in less than 50 s. These results suggest that our composites exhibit good hyperthermia properties and are promising candidates for hyperthermia treatments.

A Case of Colonic Micropapillary Carcinoma with a High Frequency of Apoptosis.

Colorectal micropapillary carcinoma (MPC) exhibits aggressive biological characteristics, with empty spaces and reversed polarity, similar to the poorly differentiated clusters (PDCs) formed from detached cancer cells. Epithelial-mesenchymal transition, which is involved in the cancer cell acquisition of apoptosis resistance, is closely linked with histological findings of MPC, PDCs, and tumor buds (TBs), with MPC and TBs considered as apoptosis-resistant features. However, we encountered a case of colonic MPC with frequent apoptosis. We examined the case using immunohistochemistry. In many of the tumor glands (TGs) of the MPC, empty spaces and tumor cell detachment toward the gland interior were observed. Moreover, TG ruptures were scattered, with PDCs adjacent to them. Apoptosis occurred mainly at the TG and PDC peripheries in the middle and deep tumor layers, and transforming growth factor beta 1 (TGF-ß1) positivity was evident in those tumor cells. Cells positive for apoptosis-related M30 were distributed mainly in the deep layer with a significant PDC and TB presence. However, apoptosis and M30 positivity were low in the TBs. Non-tumorous bud components, especially those in the deep layer, had poor ability to promptly acquire apoptosis resistance. No nuclear ß-catenin positivity was found in any of the tumor cells. Apoptosis has the potential to reciprocally produce MPC, PDCs, and TBs, with TGF-ß1 involvement.

A COL4A1 variant in a neonate with multiple intracranial hemorrhages and congenital cataracts.

A 2-day-old neonate presented with seizures, multiple intracranial hemorrhages, and bilateral congenital cataracts. Targeted next-generation sequencing of the collagen type IV alpha 1 chain (COL4A1) gene revealed a heterozygous de novo missense variant (NM_001845.6:c.2291G>A/p.Gly764Asp). This missense variant adds to the compendium of COL4A1 variants and is associated with a COL4A1-related disorder.

Development of a novel tablet machine for a tiny amount of powder and evaluation of capping tendency.

A novel single punch tablet machine was developed for a tiny amount of powder sample. This tablet machine mainly consists of upper and lower punches, single die, and conical powder feeder equipped with micro-vibrators. By using the powder feeder, mass of discharged powder can be maintained constant even if a tiny amount of powder having poor flowability is used. Motions of both upper and lower punches can be set arbitrarily. Thus, this machine enables us to prepare tablets with a tiny amount of powder sample under the same compression mechanism as conventional rotary tablet machines. Performance of the developed tablet machine was evaluated in a continuous direct tableting using a model powder with poor flowability. Thirty-four tablets (195 mg×34) having acceptable properties can be successfully prepared using no more than 10.0 g of a powder sample. We then proposed a novel in-die evaluation method of capping tendency. A new phase diagram consisting of the elastic recovery energy and the plastic deformation energy was proposed. These energies were calculated from a force-displacement profile, continuously monitored by the developed tablet machine. The results indicate that by using the new diagram the capping tendency of tablets prepared from various model powders can be well discriminated. The developed tablet machine and proposed evaluation method can contribute to a significant cost reduction and speeding up of formulation studies of oral dosage form.

Rare paraneoplastic syndromes in digestive systems caused by lung cancer.

We observed a rare case of two different digestive paraneoplastic syndromes that improved with the treatment of the neoplasms. The first syndrome was chronic intestinal pseudo-obstruction (CIPO), which is a subtype of paraneoplastic syndromes called a paraneoplastic neurological syndrome (PNS). The second was Stauffer's syndrome, which is a unique paraneoplastic syndrome characterised by non-metastatic intrahepatic cholestasis associated with neoplasms. Here, we report the case of a 55-year-old man who presented with two concurrent paraneoplastic syndromes in the digestive system. The intestinal pseudo-obstruction and elevated biliary enzyme levels improved as the lung cancer responded to chemotherapy. In this case, CIPO as a PNS led to the detection of lung cancer. To our knowledge, this is the first report of Stauffer's syndrome caused by lung adenocarcinoma.

Carcinoma showing thymus-like differentiation (CASTLE) of the salivary gland: Report of 2 cases of a hitherto under-recognized extrathyroid counterpart.

Carcinoma showing thymus-like differentiation (CASTLE) outside the thyroid gland is extremely rare. Here we report two cases of CASTLE of the major salivary gland. The tumors occurred in the parotid gland of a 31-year-old female (Case 1) and in the submandibular gland of a 40-year-old female (Case 2). Both tumors showed a lobulated growth pattern, and were histologically composed of a nested or sheet-like proliferation of carcinoma cells with round- to oval-shaped nuclei, distinct nucleoli and pale eosinophilic cytoplasm, accompanied by various degrees of lymphocytic infiltration. Immunohistochemical staining revealed that the tumors were positive for pan-cytokeratin, p40, CD5, CD117 and bcl-2. In addition, PD-L1 expression was seen in 10-90% of tumor cells. After the initial surgery, Case 1 remained tumor-free for 20 months, while Case 2 suffered lymph node recurrence at 4 months, followed by lung metastasis, which was treated with chemoradiotherapy and anti-PD-1 immune checkpoint inhibitor, resulting in a partial response. The present findings indicate that an extrathyroid counterpart of CASTLE can occur as a primary salivary gland neoplasm. Salivary CASTLEs seem to show a wide range of biological behavior, and long-term follow-up may be needed. Immune checkpoint inhibitor targeting PD-1 might become a promising treatment option in patients with CASTLE; however, further study with a larger number of cases is necessary to establish the optimal therapeutic strategy and prognostic factors for this rare cancer.

Long Spinal Cord Lesions Caused by Venous Congestive Myelopathy Associated with Intravascular Large B-cell Lymphoma.

Intravascular large B-cell lymphoma (IVLBCL) is a subtype of B-cell lymphoma, characterized by lymphoma cell proliferation within small blood vessels. We herein describe a rare case with long spinal cord lesions caused by venous congestive myelopathy associated with IVLBCL. An 81-year-old man presented with paraplegia of the lower limbs and sensory disturbances. Magnetic resonance imaging revealed intramedullary longitudinal T2-hyperintensity lesions in the thoracic cords. The patient died three months after disease onset, and a neuropathological analysis revealed predominantly atypical B-lymphocytes located sparsely in the veins of the spinal cord. IVLBCL should be considered in the differential diagnoses of long spinal cord lesions.

Periostin expression and its supposed roles in benign and malignant thyroid nodules: an immunohistochemical study of 105 cases.

BACKGROUND: Thyroid tumors are often difficult to histopathologically diagnose, particularly follicular adenoma (FA) and follicular carcinoma (FC). Papillary carcinoma (PAC) has several histological subtypes. Periostin (PON), which is a non-collagenous extracellular matrix molecule, has been implicated in tumor invasiveness. We herein aimed to elucidate the expression status and localization of PON in thyroid tumors. METHOD: We collected 105 cases of thyroid nodules, which included cases of adenomatous goiter, FA, microcarcinoma (MIC), PAC, FC, poorly differentiated carcinoma (PDCa), and undifferentiated carcinoma (UCa), and immunohistochemically examined the PON expression patterns of these lesions. RESULTS: Stromal PON deposition was detected in PAC and MIC, particularly in the solid/sclerosing subtype, whereas FA and FC showed weak deposition on the fibrous capsule. However, the invasive and/or extracapsular regions of microinvasive FC showed quite strong PON expression. Except for it, we could not find any significant histopathological differences between FA and FC. There were no other significant histopathological differences between FA and FC. Although PDCa showed a similar PON expression pattern to PAC, UCa exhibited stromal PON deposition in its invasive portions and cytoplasmic expression in its carcinoma cells. Although there was only one case of UCa, it showed strong PON immunopositivity. PAC and MIC showed similar patterns of stromal PON deposition, particularly at the invasive front. CONCLUSIONS: PON may play a role in the invasion of thyroid carcinomas, particularly PAC and UCa, whereas it may act as a barrier to the growth of tumor cells in FA and minimally invasive FC.

Nivolumab-induced liver injury with a steroid-refractory increase in biliary enzymes, in a patient with malignant mesothelioma: An autopsy case report.

This is the first autopsy report of hepatotoxicity from nivolumab immunotherapy for malignant mesothelioma. The increase in levels of biliary enzymes and randomly distributed endothelial damage were steroid-refractory, but second-line option was abandoned because of cachexia. Further discussions are needed regarding the customized management of immune-related toxicities.

Salivary Duct Carcinoma With Rhabdoid Features-No or Aberrant Expression of E-cadherin and Genetic Changes in CDH1: Immunohistochemical and Genetic Analyses of 17 Cases.

Salivary duct carcinoma is a relatively uncommon malignancy of the salivary glands; however, it frequently occurs as a carcinomatous component of carcinoma ex pleomorphic adenoma. We previously reported salivary duct carcinoma with rhabdoid features (SDCRF) as an extremely rare subtype of salivary duct carcinoma, and that it occurred as a salivary counterpart of pleomorphic lobular carcinoma of the breast (PLCB). We collected new cases of SDCRF for this study, in which we examined a total of 17 cases immunohistochemically and genetically. As it is known that PLCB exhibits loss of or aberrant E-cadherin expression and carries nonsense/missense mutations in or deletion of the CDH1 gene, we examined the CDH1 gene status of our SDCRF cases. All of the examined SDCRF cases involved the diffuse proliferation of large ovoid cells with eosinophilic cytoplasm and eccentric nuclei, which displayed reduced cell-cell adhesion. Most cases were positive for pan-cytokeratin, androgen receptor, gross cystic disease fluid protein-15, SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1, and WI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily A member 4, whereas they were negative for vimentin. No and decreased/cytoplasmic E-cadherin expression was observed in 11 and 4 of 17 cases, respectively, whereas no and decreased/cytoplasmic ß-catenin expression were observed in 10 and 5 of 17 cases, respectively. Among the 11 cases that could be genetically analyzed, a nonsense mutation (1 case), missense mutations (6 cases), and insertions (1 case) were detected in the CDH1 gene. In conclusion, we propose that SDCRF is the salivary counterpart of PLCB due to its morphology and immunophenotype, and the genetic status of CDH1.

[Case of visceral varicella-zoster virus infection after autologous peripheral blood stem cell transplantation in which severe abdominal pain preceded the skin rash].

We report a 54-year-old man who developed visceral varicella-zoster virus (VZV) infection after autologous peripheral blood stem cell transplantation (auto-PBSCT) without using immunosuppressive agents for multiple myeloma. He suffered from severe abdominal pain 2 months after auto-PBSCT, and morphine chloride was needed to control it. Since the characteristic skin rash of VZV infection appeared over his entire body on the seventh hospital day, aciclovir was immediately started with favorable results. It is extremely difficult to diagnose VZV infection when severe abdominal pain proceeds and the eruptions characteristic of VZV infections are absent. This may also result in devastating delays in effective antiviral treatment. The increase in fat density around the celiac trunk and the root of the superior mesenteric artery on computed tomography shown in this case may has contributed to the correct diagnosis of visceral VZV infection.

Involvement of Annexin A2 Expression and Apoptosis in Reverse Polarization of Invasive Micropapillary Carcinoma of the Breast.

Invasive micropapillary carcinoma (IMPC) is characterized by pseudopapillary tumor-cell clusters with a reverse polarity (RP) floating in lacunar spaces, with aggressive biological characteristics. The RP prevention is considered to inhibit IMPC, but its pathogenic mechanisms remain unclear. Annexin A2 (ANX A2), a cell-polarity protein, is known to be involved in lumenogenesis. ANX A2 expression is immunohistochemically examined, as well as both epithelial membrane antigen (EMA) and mucin-1 glycoprotein (MUC-1), the gold-standard markers for luminal differentiation, in the background tumor components of a case of IMPC. The following findings were noticed: (1) Apoptosis was scattered with peripheral apoptotic vacuolar change; (2) EMA and MUC-1 expressions were found, rimming the peripheral apoptotic vacuoles (including the contact surface with neighboring tumor cells), and these positions corresponded to the ones with a distinct ANX A2 positivity; and (3) partially detached tumor cells showed distinct positivity of three proteins at the stroma-facing surface, which is consistent with a RP. Taken together, frequent apoptosis in tumor cells with membranous accumulation of ANX A2 is considered to be indispensable for the reverse polarization of IMPC, and that secondary necrosis following apoptosis induces the cell-polarity disorder and creates detached tumor cells with a RP.

A case of small well-differentiated hepatocellular carcinoma with marked lymphocytic infiltrate.

We herein report a case of well-differentiated small hepatocellular carcinoma (HCC) with severe lymphocytic infiltrate (SLI) in a 55-year-old male patient with HCV-related cirrhosis. The patient had been followed-up because of HCV-related cirrhosis. He was found to have two small nodules in S8 by imaging techniques, and he underwent S8 segmentectomy. The resected liver showed two small nodules. Both were encapsulated, well-defined, solid, reddish and expansive nodules with fibrous septa. They measured 8 × 8 mm and 15 × 10 mm, respectively. Histologically, both tumours were pure HCC; the smaller showed SLI with lymphocytes/HCC cells ratio over 20, while the larger showed mild lymphocytic infiltration with lymphocytes/HCC cells ratio of 0.8. The smaller HCC was well-differentiated (trabecular thickness <3) HCC-SLI with Edmondson II = I cytologic atypia, while the larger was moderately-differentiated (trabeculae >3) HCC (Edmondson II>III>I). Extremely well-differentiated Edmondson I HCC or adenomatous hyperplasia areas were seen in the periphery of both HCCs. The patterns of SLI could be classified into the following three: sinusoids (S) type, portal tract (PT) type, lymph follicle (LF) type. In S-type, lymphocytes were infiltrated between the trabeculae. In PT-type, SLI was found to arise from extension from already inflamed PT within HCC or neighboring PT. The HCC cells frequently exhibited moth-eaten or piece meal necrosis in PT-type. In LF-type, lymphocytes were activated, and nuclear dusts were noted. It appeared that LF-type has arisen from preexisting S-type and/or PT-type. We speculated that the entry of SLI was from S in S-type, from incorporated inflamed PT in PT-type, and from both in LF-type. The approximate overall positive ratios of lymphoid cells among inflammatory cells were as follows: CD20 50%, CD3 70%, CD4 50%, CD8 30%, CD138 3%, CD163 40%, granzyme B 2%, smooth muscle actin (SMA) 30%, CD31 30%, CD21 2%, S100 3%, bcl-2 10%, CK19 1%, CD10 1%, CD30 0%, CD56 0% and Ki67 labeling index = 5%. EBV-ISH and HPV IHC were negative. Interestingly, Kupffer cells had myofibroblastic antigen in addition to macrophage antigens, and stellate cells expressed macrophage antigens aside from myofibroblastic antigens. These data suggest that, in the present case, pan-B-cells, pan-T-cells, helper T-cells, cytotoxic T-cells, plasma cells, macrophages, Kupffer cells, stellate cells, myofibroblasts, fibroblasts, endothelial cells, dendritic cells, Langerhans cells, and toxic molecules may play roles in tumour immunology.

A case of small hepatocellular carcinoma with malignant ductular reaction.

Herein reported is the unique case of a small hepatocellular carcinoma (HCC) with several foci of a minor (10% in area) component of "malignant ductular reactions". The patient was 51-year-old man who was a drinker. HBV/HCV were negative. The tumor was small (12×10×11 mm), solid, expansile and reddish-brown, and contained fibrous septa. The background was cirrhotic without alcoholic features. Histologically, the tumor was well differentiated HCC, and, besides the HCC, it contained several small foci consisting of the following four biliary epithelial elements: clusters of small cells (CSC), ductules (D), ductular hepatocytes (DH), and bile ducts (BD). The proportion of area was as follows: HCC 90%, CSC 3%, D 3%, DH 2%, and BD 2%. These non-HCC elements were intimately admixed and formed several foci that were characteristically located in the fibrous septa (FS), except for CSC which were situated among HCC cells close to FS. There were gradual merges between HCC and CSC, CSC and D, D and DH, and D and BD, respectively. Cells of CSC and D resembled rat oval cells. Cells of these four elements had atypical features regarded as malignant. Immunohistochemically (IHC), HCC were positive for arginase, HepPar1, and less frequently CK7. CSC were positive for CK7. D were positive for arginase, HepPar1, CK7, CK19, EMA, and EpCAM. DH were positive for arginase, HepPar1, and CK7. BD were positive for CK7, CK19, EMA, EpCAM and mucin. Although such tumors as this have been termed stem cell-related cancers, our case lacked definite evidence for stem cell origin in histology as well as in the IHC that showed negativity for KIT, CD34, and OCT3/4. The above findings suggest that CSC, D, DH and BD are analogous to the ductular reaction seen in hepatic inflammation. Therefore, we termed the phenomenon "malignant ductular reaction". It is suggested in the present tumor that at first only HCC developed, and then HCC cells in the interface with FS transformed to CSC, like a fetal ductal plate. Then, the CSC gave rise to D, which in turn led to DH and BD in FS, all findings of which are most likely sequential considering embryonic biliary development. The idea that the present tumor was at first D carcinoma and then D developed on one hand into CSC and HCC, and on the other into DH and BD seems possible, but its probability appears low because the vast majority of the present tumor had the phenotype of HCC.