Clinicopathologic and molecular study of superficial CD34-positive fibroblastic tumours mimicking atypical fibrous histiocytoma (dermatofibroma).

AIMS: Superficial CD34-positive fibroblastic tumour (SCD34FT) is an uncommon but distinctive low-grade neoplasm of the skin and subcutis that shows frequent CADM3 expression by immunohistochemistry (IHC). In this study, prompted by an index case resembling 'atypical fibrous histiocytoma (FH)' that was positive for CADM3 IHC, we systematically examined a cohort of tumours previously diagnosed as 'atypical FH' by applying CADM3 and fluorescence in situ hybridization (FISH) for PRDM10 rearrangement, to investigate the overlap between these tumour types. METHODS AND RESULTS: Forty cases of atypical FH were retrieved, including CD34-positive tumours (n = 20) and CD34-negative tumours (n = 20). All tumours were stained for CADM3. All CADM3-positive tumours were evaluated by FISH to assess for PRDM10 rearrangement. Eleven CD34-positive tumours (11/20, 55%) coexpressed CADM3 and were reclassified as SCD34FT. None (0/20) of the CD34-negative atypical FH were CADM3-positive. Reclassified SCD34FT (10/11) arose on the lower extremity, with frequent involvement of the thigh (n = 8). Features suggestive of atypical FH were observed in many reclassified cases including variable cellularity, spindled morphology, infiltrative tumour margins, collagen entrapment, epidermal hyperpigmentation, and acanthosis. Variably prominent multinucleate giant cells, including Touton-like forms, were also present. An informative FISH result was obtained in 10/11 reclassified tumours, with 60% (6/10) demonstrating PRDM10 rearrangement. CONCLUSION: A significant subset of tumours that histologically resemble atypical FH, and are positive for CD34, coexpress CADM3 and harbour PRDM10 rearrangement, supporting their reclassification as SCD34FT. Awareness of this morphologic overlap and the application of CADM3 IHC can aid the distinction between SCD34FT and atypical FH.

Peer-to-peer validation of Ki-67 scoring in a pathology quality circle as a tool to assess interobserver variability: are we better than we thought?

Ki-67, a nuclear protein expressed in all stages of cellular proliferation, is a valuable tool to assess tumor proliferation and has been linked to more aggressive tumor behavior. However, interlaboratory staining heterogeneity and inter-observer variability challenge its reproducibility. Round Robin tests are a suitable tool to standardize and harmonize immunohistochemical and molecular analyses in histopathology. The study investigates the interrater and interlaboratory reproducibility of Ki-67-scoring using both manual and automated approaches. Unstained TMA slides comprising diverse tumor types (breast cancer, neuroendocrine tumors, lymphomas, and head and neck squamous cell carcinoma) were distributed to six pathology laboratories, each employing their routine staining protocols. Manual and automated scoring methods were applied, and interrater and interlaboratory agreement assessed using intraclass correlation coefficients (ICC). The results highlight good-to-excellent reliability overall, with automated scoring demonstrating higher consistency (ICC 0.955) than manual scoring (ICC 0.871). Results were more variable when looking at the individual entities. Reliability remained good for lymphomas (ICC 0.878) and breast cancer (ICC 0.784) and was poor in well-differentiated neuroendocrine tumors (ICC 0.354). This study clearly advocates standardized practices and training to ensure consistency in Ki-67-assessment, and it demonstrates that this can be achieved in a peer-to-peer approach in local quality-circles.

[Gastric and colic digestive localizations of myeloma; 3 case studies and literature review]. / Localisations digestives gastriques et coliques de myélomes ; étude de 3 cas et revue de la littérature.

Multiple myeloma is a malignant plasma cell proliferation located in the bone marrow and bones. It can secondarily manifest with extraosseous involvement, but the gastro-intestinal tract locations are rare. We report 3 cases of gastric and colonic localizations of myeloma in two males and one female, aged 66, 71 and 77years. Multiple myeloma had been diagnosed 1 to 7years before. Digestive symptoms were epigastric pain, rectal bleeding or an obstructive syndrome. Endoscopy revealed ulcerated and budding tumors in the stomach, and nodular pseudo-polypoid tumor formations or an ulcerated erythematous area in the colon. Histopathological examination of the biopsies showed a diffuse tumor cell proliferation in the lamina propria composed of cells with a plasmacytoid or plasmablastic appearance, expressing plasma cell markers such as CD138 on immunohistochemistry. The 3 patients died in the weeks following the diagnosis. The prognosis of digestive localizations of multiple myeloma remains very poor despite new therapies. In the presence of any digestive symptoms in these patients with multiple myeloma, more systematic endoscopy may allow an earlier diagnosis and the implementation of more effective therapies.

Diagnostic Value of SALL4 and OCT3/4 in Pediatric Testicular Tumors.

Testicular tumors (TTs) are rare in children, posing diagnostic and therapeutic challenges. This retrospective study evaluates the diagnostic and prognostic utility of SALL4 and OCT3/4 in pediatric TTs. We analyzed 18 cases of different types of TTs using immunohistochemistry (IHC) to assess SALL4 (Spalt-like transcription factor 4) and OCT3/4 (Octamer binding transcription factor 3/4) expression. SALL4 was positive in 83.3% of tumors, while OCT3/4 was positive in 38.9% of tumors, with a significantly higher prevalence in patients aged 12-18 years compared to those aged 0-11 years (p = 0.013). Mixed germinal cell tumors were significantly more frequently associated with OCT3/4 (p = 0.003), and a high immunostaining expression for SALL4 was observed primarily in yolk sac tumors and embryonal carcinoma. Our findings suggest that SALL4 and OCT3/4 immunostaining can aid in accurate diagnosis and treatment planning, and underscores the importance of OCT3/4 as a predictive factor in pediatric testicular tumors, highlighting its substantial correlation with tumor type and its impact on treatment response. These markers may guide personalized therapeutic strategies, potentially improving patient outcomes.

Prognostic Evaluation of Piezo2 Channels in Mammary Gland Carcinoma.

In the last decade, a group of Ca2+ channels called Piezo were discovered, demonstrating a decisive role in the cellular response to mechanical stimuli and being essential in the biological behavior of cells regarding the extracellular compartment. Several investigations have suggested a potential role in carcinogenesis, with a tumor suppressor role in some cases but increased expression in several high-grade neoplasms. Regarding Piezo2 expression in mammary gland neoplasms, a protective role for Piezo2 was initially suggested, but a subsequent study demonstrated a relationship between Piezo2 expression and the highly aggressive triple-negative phenotype of breast carcinoma. A cohort of 125 patients with clinical follow-up was chosen to study Piezo2 expression and clarify its clinical implications using the same immunohistochemical evaluation performed for other breast carcinoma parameters. Fisher's exact test was chosen to identify potential relationships between the different variables. A significant association was found with the Ki67 proliferation index, but not with mitoses. The tendency of most proliferative tumors was to have an increased score for Piezo2. A similar association was found between Piezo2 expression and perineural invasion.

Stimulator of Interferon Genes Protein (STING) Expression in Cancer Cells: A Tissue Microarray Study Evaluating More than 18,000 Tumors from 139 Different Tumor Entities.

Stimulator of interferon genes protein (STING) activates the immune response in inflammatory cells. STING expression in cancer cells is less well characterized, but STING agonists are currently being evaluated as anticancer drugs. A tissue microarray containing 18,001 samples from 139 different tumor types was analyzed for STING by immunohistochemistry. STING-positive tumor cells were found in 130 (93.5%) of 139 tumor entities. The highest STING positivity rates occurred in squamous cell carcinomas (up to 96%); malignant mesothelioma (88.5%-95.7%); adenocarcinoma of the pancreas (94.9%), lung (90.3%), cervix (90.0%), colorectum (75.2%), and gallbladder (68.8%); and serous high-grade ovarian cancer (86.0%). High STING expression was linked to adverse phenotypes in breast cancer, clear cell renal cell carcinoma, colorectal adenocarcinoma, hepatocellular carcinoma, and papillary carcinoma of the thyroid (p < 0.05). In pTa urothelial carcinomas, STING expression was associated with low-grade carcinoma (p = 0.0002). Across all tumors, STING expression paralleled PD-L1 positivity of tumor and inflammatory cells (p < 0.0001 each) but was unrelated to the density of CD8+ lymphocytes. STING expression is variable across tumor types and may be related to aggressive tumor phenotype and PD-L1 positivity. The lack of relationship with tumor-infiltrating CD8+ lymphocytes argues against a significant IFN production by STING positive tumor cells.

Expression of programmed cell death protein 1 and programmed cell death ligand 1 in feline injection site fibrosarcomas.

Feline injection site fibrosarcomas represent a unique challenge in veterinary oncology due to their association with injection sites and aggressive behaviour. The study explores the expression of immune checkpoints programmed cell death protein 1 and programmed cell death ligand 1 in the malignancy, aiming to unravel their potential significance in tumour progression. The study included 31, archival diagnostic specimens of feline fibrosarcomas, located in the common injection sites. The programmed cell death protein 1 and programmed cell death ligand 1 expression in tumour cells and tumour infiltrating lymphocytes were assessed by immunohistochemical methods. Programmed cell death protein 1 and programmed cell death ligand 1 expression were observed in 84% and 81% of cases, respectively. In tumour infiltrating lymphocytes the PD-1 expression was observed in 71% of cases. Notably, higher programmed cell death protein 1 expression correlated with tumour grade and heightened inflammation score, suggesting a potential association with tumour aggressiveness. Similarly, programmed cell death ligand 1 expression exhibited a positive correlation with tumour grade and inflammation score. The observed findings suggest a potential role for programmed cell death protein 1 and programmed cell death ligand 1 in tumour progression and immune response within the tumour microenvironment. Moreover, this study contributes to a deeper understanding of feline injection site fibrosarcoma pathogenesis, emphasizing the importance of considering immunological perspectives in developing effective treatment strategies for this challenging condition. Further investigations are warranted to advance our knowledge and refine therapeutic approaches for feline injection site fibrosarcoma management.

Cancer Stem Cells (CD44+/CD24-), RAD6, DDB2 Immunohistochemistry Expression and IHC-UNEDO Scoring System As Predictor of Ovarian Cancer Chemoresistance.

Backgrounds: Ovarian cancer is a deadly women cancer with many chemoresistance after standard treatment. Ovarian cancer tissues' CD44+/CD24- (CSCs), RAD6 overexpression and DDB2 underexpression are associated with chemoresistance, recurrence, and poor prognosis of the disease because of the existence of cancer stem cells (CSCs). We tried to analyze the expression of those three proteins while building a predictor scoring system to predict the ovarian cancer chemoresistance from the ovarian cancer tissue immunohistochemistry. Materials and Methods: We conducted a cohort study of 64 patients divided into two groups (32 patients in each group) at the Cipto Mangunkusumo, Tarakan, Dharmais, and Fatmawati Hospital which are located in Jakarta city, Indonesia. The patients underwent cytoreductive debulking and histopathological examination continued by six series of chemotherapy followed by six months of observation. We divided the groups into chemoresistant and chemosensitive by using Response Criteria in Solid Tumors (RECIST) criteria. Ovarian cancer tissue immunohistochemistry tests were then performed to count the CSCs, RAD6 and DDB2 expressions. Results: We found relationship between increased CSCs, RAD6 and reduced DDB2 (p < 0.05) expression in ovarian cancer tissue with the chemoresistance. A possible predictor scoring system named IHC-UNEDO scoring was built to aid the ovarian cancer chemoresistance prediction. Conclusions: The conclusion is that CSCs, RAD6 and DDB2 expressions are significantly associated with ovarian cancer chemoresistance, and IHC-UNEDO scoring should be considered as a tool to predict ovarian cancer chemoresistance.

NIR-II light therapy improves cognitive performance in MPTP induced Parkinson's disease rat models: A preliminary experimental study.

Cognitive impairment is an important component of non motor symptoms in Parkinson's disease (PD), and if not addressed in a timely manner, it can easily progress to dementia. However, no effective method currently exists to completely prevent or reverse cognitive impairment associated with PD. We therefore aimed to investigate the therapeutic effect of near-infrared region II light (NIR-II) region illumination on cognitive impairment in PD through behavioral experiments (water maze and rotary rod) and multiple fluorescence immunohistochemistry techniques. The 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced group was compared with the MPTP- untreated rat group, showing a significant reduction in escape latency and significant increase in the fall latency in the MPTP-treated group. The horizontal analysis results indicated that NIR-II phototherapy improved the learning and cognitive abilities as well as coordination and balance abilities of rats. Post-treatment, the MPTP rats showed significantly shortened, escape latency, prolonged target quadrant residence time, and prolonged fall latency compared with pre-treatment. The longitudinal analysis results reaffirmed that NIR-II phototherapy improved the learning and cognitive abilities as well as coordination and balance abilities of rats. The multiple fluorescence immunohistochemistry analysis trend plot showed that the activated microglia and astrocytes in the hippocampus were highest in MPTP-induced PD untreated group, moderate in MPTP-induced PD treatment group, and lowest in the control group. Our data indicates that NIR-II illumination improves learning and cognitive impairment as well as coordination and balance abilities in PD rats by downregulating the activation of microglia and astrocytes in the hippocampus.

Myeloid sarcoma with maxillary gingival swelling as the initial symptom: A case report and review of literature.

BACKGROUND: Myeloid sarcoma (MS), also referred to as granulocytic sarcoma or chloroma, is a rare type of extramedullary malignant tumor. MS comprises primitive granulocytic precursor cells that play a key role in the early stages of white blood cell development. Notably, the occurrence of this tumor in the gingiva is rare. CASE SUMMARY: The present study reported the case of MS with gingival swelling in the maxillary region, with aleukemic presentation in a 32-year-old male patient. Following two courses of chemotherapy, computed tomography of the region demonstrated complete clearance of the tumor. At the 12-month follow-up appointment, the patient was in a stable condition with the absence of progression. The etiology, clinical features, diagnosis, and relevant treatment of MS are discussed in the present study. CONCLUSION: Diagnosis of MS may be confirmed following histological and immunohistochemical examinations.

Rhabdomyosarcoma in a Rabbit.

A geriatric Holland Lop rabbit presented for acute lameness. A pathologic fracture of the right distal femur associated with a pleomorphic rhabdomyosarcoma was diagnosed, and staging radiographs showed no overt metastasis upon initial presentation. The limb was amputated and submitted for microscopic examination. Immunohistochemical evaluation revealed the neoplastic cells were positive for desmin and MyoD1, and negative for cytokeratin AE1/AE3, CD204, IBA-1, and SMA. Gross, histologic, and immunohistochemical evaluation confirmed a diagnosis of pleomorphic rhabdomyosarcoma. The patient died 396 days after amputation, and a post-mortem examination showed metastatic sarcoma to multiple organs.

Solitary neurofibroma confined to inferior rectus muscle tendon: a case report.

The present study reports a case of solitary neurofibroma attached to the Inferior Rectus (IR) muscle tendon in a 24-year-old healthy woman and reviews the relevant literature regarding the clinical presentation, diagnosis, and management of this uncommon tumor. The patient underwent successful surgical resection of the tumor, leading to the resolution of associated symptoms (left lower eyelid protrusion and redness). Pathological examination confirmed the diagnosis of neurofibroma based on characteristic histopathological and immunohistochemical markers. This case report underscores the rarity of solitary neurofibromas and primary neoplasms of orbit and ocular adnexa. We also discuss the background of solitary neurofibromas originating from orbit and ocular adnexa. The successful management of this case through surgical resection highlights the importance of accurate diagnosis and tailored treatment strategies. To the best of our knowledge, this is the first reported solitary neurofibroma confined solely to the IR tendon.

Spatial correlation between in vivo imaging and immunohistochemical biomarkers: A methodological study.

In this study, we present a method that enables voxel-by-voxel comparison of in vivo imaging to immunohistochemistry (IHC) biomarkers. As a proof of concept, we investigated the spatial correlation between dynamic contrast enhanced (DCE-)CT parameters and IHC biomarkers Ki-67 (proliferation), HIF-1α (hypoxia), and CD45 (immune cells). 54 whole-mount tumor slices of 15 laryngeal and hypopharyngeal carcinomas were immunohistochemically stained and digitized. Heatmaps of biomarker positivity were created and registered to DCE-CT parameter maps. The adiabatic approximation to the tissue homogeneity model was used to fit the following DCE parameters: Ktrans (transfer constant), Ve (extravascular and extracellular space), and Vi (intravascular space). Both IHC and DCE maps were downsampled to 4 × 4 × 3 mm[3] voxels. The mean values per tumor were used to calculate the between-subject correlations between parameters. For the within-subject (spatial) correlation, values of all voxels within a tumor were compared using the repeated measures correlation (rrm). No between-subject correlations were found between IHC biomarkers and DCE parameters, whereas we found multiple significant within-subject correlations: Ve and Ki-67 (rrm = -0.17, P < .001), Ve and HIF-1α (rrm = -0.12, P < .001), Ktrans and CD45 (rrm = 0.13, P < .001), Vi and CD45 (rrm = 0.16, P < .001), and Vi and Ki-67 (rrm = 0.08, P = .003). The strongest correlation was found between IHC biomarkers Ki-67 and HIF-1α (rrm = 0.35, P < .001). This study shows the technical feasibility of determining the 3 dimensional spatial correlation between histopathological biomarker heatmaps and in vivo imaging. It also shows that between-subject correlations do not reflect within-subject correlations of parameters.

ISLET-1 expression in soft tissue neoplasms reveals high sensitivity but moderate specificity for desmoplastic small round cell tumors and potential utility as a diagnostic biomarker.

ISLET-1 (ISL1) is a LIM-homeodomain transcription factor. Selective ISL1 expression is shown in neuroendocrine, non-neuroendocrine, and some soft tissue tumors including desmoplastic small round cell tumor (DSRCT). We assessed the specificity of ISL1 (clone EP283, 1:500, Cell Marque) in 288 soft tissue tumors, which included 17 DSRCTs and other histologic mimics. Positive staining threshold for ISL1 was set to >10 % of neoplastic cell nuclei at moderate intensity. ISL1 IHC was positive in 15/16 (94 %) DSRCTs with 75 % showing diffuse (>50 %) expression. ISL1 was positive in 1/10 (10 %) Ewing sarcomas (EWS), 7/13 (54 %) alveolar rhabdomyosarcoma (RMS), 14/22 (63 %) embryonal RMS, 7/14 (50 %) synovial sarcomas, 15/16 (93 %) neuroblastoma, 1/5 (20 %) Wilms tumor, 2/4 (50 %) olfactory neuroblastoma, and all 9 Merkel cell carcinomas. Other tumors, including all CIC::DUX4 sarcomas, were negative except 3/27 leiomyosarcomas, and 1 each of angiosarcoma, myxoid liposarcomas, inflammatory myofibroblastic tumor, malignant peripheral nerve sheath tumor, tenosynovial giant cell tumor, dedifferentiated LPS, and 1 ectomesenchymoma. In summary, among the soft tissue tumors tested, ISL1 is a highly sensitive but moderately specific marker for DSRCT and may be useful to distinguish from round cell mimics including EWS and CIC::DUX4 sarcomas. The oncogenic role of ISL1 in these tumors warrants further investigation.

Evaluation of immunophenotype and inflammation in canine mammary neoplasms with solid arrangement.

Morphological and immunohistochemical studies of solid arrangement canine mammary carcinomas have shown that the different histological types may be characterized by proliferation of epithelial and/or myoepithelial cells. However, little is known about immunophenotypes and the importance of inflammation as prognostic factors in these neoplasms. The objective of the present study was to characterize the immunophenotype and degree of inflammation in the solid type of canine mammary neoplasm and to investigate their association with metastasis, Ki-67 index, tumour size, necrosis and survival. Sixty-five carcinomas with solid pattern, basaloid carcinomas, solid papillary carcinomas, malignant adenomyoepitheliomas (MAMEs) or malignant myoepitheliomas (MMEs) were investigated. Luminal A, luminal B HER2 negative and HER2 positive, HER2 overexpressed and triple negative immunophenotypes were immunolabelled as were Ki-67 protein and cyclooxygenase-2 (Cox-2). Histological peritumoural and intratumoural inflammatory infiltrates were graded (distribution × intensity) and the presence of necrosis identified. We found a statistical difference between histological types and immunophenotypes, with MME and MAME having a higher occurrence of luminal A, whereas most neoplasms had the luminal B HER-negative immunophenotype. There was no correlation between immunophenotype and degree of peri- and intratumoural inflammation, nodal metastasis, necrosis or tumour size. An increased degree of peri- and intratumoural inflammation was significantly associated with lymph node metastasis, and more severe intratumoural inflammation was associated with the presence of tumour necrosis. Tumour size, Ki-67 index and Cox-2 score were not associated with inflammation in either peri- or intratumoural regions. No difference was observed in survival in relation to immunophenotype or degree of inflammation, but the Cox regression model revealed that nodal metastasis influenced the risk of death.

Giant intrapulmonary solitary fibrous tumor.

Solitary fibrous tumor (SFT) is a soft tissue tumor of mesenchymal origin involving, most commonly, the pleura. Intrapulmonary SFT is a slow-growing tumor that rarely reaches giant forms. SFTs are asymptomatic and often randomly discovered by routine chest X-rays. The diagnosis requires histopathological and immunohistochemical (IHC) examinations. Most of the SFTs are benign and present an indolent course. Larger tumors are more likely to be malignant and consequently associated with a worse prognosis. Despite having histopathological criteria for malignancy, the behavior of SFTs is challenging to predict. We report a case of giant intrapulmonary SFT of intermediate risk.

Clear cell myomelanocytic tumor of ligamentum teres.

Clear cell myomelanocytic tumor (CCMMT) of the falciform ligament/ligamentum teres is a rare hepatic tumor, a variant of the perivascular epithelioid cell tumor (PEComa) family. CCMMT is the rarest variant of hepatic PEComas. Only a few cases of CCMMT have been reported in the English literature. Because of its rarity, less is known about its biological behavior. We present a case of a 31-year-old female who complained of abdominal pain, bilious vomiting, and abdominal fullness over two months. The radiological impression was of focal nodular hyperplasia. The histological examination of the resection specimen revealed a well-circumscribed tumor arranged in fascicles, sheets, and a whorling pattern. The tumor cells were spindle to epithelioid shaped with abundant clear to pale eosinophilic cytoplasm. The tumor cells expressed both myoid (smooth muscle actin) and melanocytic (MelanA and HMB45) markers, while they were negative for hepatocytic and vascular markers. Thus, based on histology and immunohistochemistry, a diagnosis of CCMMT was made. This case presents the diagnostic challenges of CCMMT and discusses the differential diagnosis with a literature review.

Kaiso Expression in Triple Negative Breast Cancer in a Tertiary Hospital in Ghana.

Background: Breast cancer has produced more lost disability-adjusted life years (DALYs) than any other type of cancer. The prevalence of the disease, especially triple negative breast cancer (TNBC) in Africa is on the rise, with poor survival rates. With the great advancements in treatments of breast cancers, that of TNBC is still a challenge due to its narrowed treatment options and poor disease prognosis. This research seeks to explore the expression of kaiso in Ghanaian breast cancer and how they may modulate clinicopathological features, and disease prognosis. Methodology: A cross-sectional retrospective study was conducted on formalin-fixed paraffin-embedded (FFPE) breast cancer tissues retrieved from the archives of the pathology unit of Komfo Anokye Teaching Hospital (KATH). Immunohistochemistry assessment was performed on haematoxylin and eosin-stained slides selected for tissue microarray construction. Data were analysed using SPSS version 28 and Microsoft excel 2013. Results: 55.3% of the cases tested negative to progesterone receptor (PR), oestrogen receptor (ER), and human epidermal growth receptor 2 (HER2). There were significant associations between menopausal status and molecular subtype (p=0.010), Kaiso expression and histological diagnoses (<0.001) and Kaiso against lymphovascular invasion (0.050). However, there were no significant associations between Kaiso localization and the clinicopathological features although 63.9% of the expression was seen in the nucleus. Conclusion: The study indicates that Kaiso is highly expressed in Ghanaian TNBC and likely associated with worse outcomes in aggressive tumour types.

E-cadherin mutational landscape and outcomes in breast invasive lobular carcinoma.

Invasive lobular carcinomas (ILC) are characterized by a loss of E-cadherin expression and CDH1 gene inactivation. Diagnostic reproducibility for this tumor type is currently suboptimal and could be improved by a better understanding of its histomolecular and clinical heterogeneity. We have analyzed the relationship between presence, type or position of CDH1 mutations, E-cadherin expression and clinicopathological features (including outcome) in a retrospective series of 251 primary ILC with long follow-up (median: 9.5 years). The mutational status of E-cadherin gene (CDH1) was determined by RNA sequencing from frozen tumor samples. E-cadherin immunohistochemistry (IHC) was performed with antibodies directed against the intracellular domain (clone 4A2C7) and the extracellular domain (clone NCH38). IHC expression of p120 and ß-catenin was also assessed in E-cadherin diffusely positive cases. Three major patterns of E-cadherin membrane expression were identified by IHC, with good agreement between the two clones (overall concordance: 83.8%, Kappa 0.67): null/focal expression (≤10%) (72.8% of cases for 4A2C7, 83.8% for NCH38), heterogeneous expression (11-89%) (19.2% of cases for 4A2C7, 6.9% for NCH38) and diffuse expression (≥90%) (8% of cases for 4A2C7, 9.3% for NCH38). E-cadherin membranous expression, when present, was abnormal (incomplete labeling and/or reduced intensity). ILC with diffuse E-cadherin expression showed abnormal ß-catenin or p120-catenin staining in 21% of cases. Interestingly, these cases with diffusely expressed E-cadherin had a CDH1 mutation rate as high as the E-cadherin null/focal cases (∼70%), but were enriched in non-truncating mutations. Regarding CDH1 mutation location, intracytoplasmic domain mutations correlated with a divergent E-cadherin IHC phenotype between the two antibodies (4A2C7 ≤10% / NCH38 ≥10%). Clinico-pathological correlation analyses found that stromal amount (inversely correlated with tumor cellularity) and TILs were less abundant in ILC with E-cadherin null/focal cases. In addition, CDH1 truncating mutations were associated with radio-histological size discordance, and were identified in multivariate survival analysis as an independent poor prognosis factor in terms of metastasis risk and breast cancer related mortality. Overall, our study highlights the importance of the precise mutational status of CDH1 in the clinical, radiological, histological and phenotypic expression of lobular carcinomas. These findings should be taken into account in future attempts to improve diagnostic criteria or methods for ILC, as well as for clinico-biological studies dedicated to this tumor type.

Rosai-Dorfman Disease of pancreas: rare aetiology mimicking malignancy.

Rosai-Dorfman disease (RDD) is a non-Langerhans cell histiocytosis which usually presents as painless lymphadenopathy. Extranodal involvement is known to occur in various organs, and less than ten cases with primary pancreatic involvement have been reported previously. This case report details the clinical course of an elderly female, presenting with upper abdominal discomfort and imaging suggestive of malignancy. Multiple non-diagnostic fine-needle aspirations were followed by surgical intervention. Histopathological evaluation revealed a pancreatic mass with characteristic features of RDD. The large hallmark RDD histiocytes showed pale, watery-clear cytoplasm, central round nucleus, and prominent nucleolus, with and without lymphocyte emperipolesis. The RDD histiocytes showed positive immunostaining for CD68, CD163, S100 (nuclear and cytoplasmic), OCT-2, Cyclin D1 and are negative for CD1a, Factor XIIIa, fascin and langerin. This case underscores the importance of considering RDD in the differential diagnosis of pancreatic masses alongwith comprehensive evaluation, multidisciplinary approach and pancreatic core needle biopsy evaluation.