Clinicopathologic and Molecular Characterization of Inflammatory Bowel Disease-Associated Neuroendocrine Carcinomas and Mixed Neuroendocrine-Non-Neuroendocrine Neoplasms.

The pathogenesis of neuroendocrine carcinomas (NECs) and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) in the gastrointestinal tract remains poorly understood. This study aims to characterize the clinicopathologic and molecular features of NEC/MiNEN in patients with inflammatory bowel disease (IBD). Eighteen surgically resected IBD-associated intestinal carcinomas with a minimum of 30% neuroendocrine component were collected from 6 academic centers and compared with a control group of 12 IBD-associated carcinomas lacking neuroendocrine differentiation. Both groups exhibited a male predominance and similar age distribution. The NEC/MiNEN group was more likely to have a higher percentage of Crohn disease (9/18 vs 1/12; P = .024), occur in the rectum (9/18 vs 3/12) and small intestine (4/18 vs 0/12) (P < .01), be diagnosed on resection without a preceding biopsy (6/18 vs 0/12; P = .057), and have unidentifiable precursor lesions (10/18 vs 1/12; P = .018) than the control group. Synchronous carcinoma, advanced tumor stage (pT3 and pT4), and lymph node metastasis occurred at similar rates; however, the NEC/MiNEN group had a higher incidence of angiovascular invasion (14/18 vs 4/12; P = .024), distant metastasis (8/18 vs 1/12; P = .049), mortality (8/18 vs 2/12; P = .058), and worse survival (Kaplan-Meier; P = .023) than the control group. All tested cases were mismatch repair proficient. A Ki-67 proliferation index ranged from 25% to 100%. Next-generation sequencing in 11 NEC/MiNEN cases revealed low tumor mutational burdens but complex genetic abnormalities commonly involving TP53 (9/11; 82%), FBXW7 (4/11; 36%), and APC (3/11; 27%) genes, with the other genetic alterations randomly occurring in 1 or 2 cases. The neuroendocrine component, which shared similar molecular alterations as the nonneuroendocrine component, was subcategorized into intermediate (G3a) and high grade (G3b); the higher grade correlated with more genetic alterations. In conclusion, IBD-associated NEC/MiNEN shows diverse histologic features, variable precursor lesions, intricate genetic abnormalities, and aggressive biologic behavior. The classification and grading of gastrointestinal NEC/MiNEN may be refined for better clinical management.

Analyses of combined Merkel cell carcinomas with neuroblastic components suggests that loss of T antigen expression in Merkel cell carcinoma may result in cell cycle arrest and neuroblastic transdifferentiation.

Merkel cell carcinoma (MCC) is an aggressive skin cancer frequently caused by genomic integration of the Merkel cell polyomavirus (MCPyV). MCPyV-negative cases often present as combined MCCs, which represent a distinctive subset of tumors characterized by association of an MCC with a second tumor component, mostly squamous cell carcinoma. Up to now, only exceptional cases of combined MCC with neuroblastic differentiation have been reported. Herein we describe two additional combined MCCs with neuroblastic differentiation and provide comprehensive morphologic, immunohistochemical, transcriptomic, genetic and epigenetic characterization of these tumors, which both arose in elderly men and appeared as an isolated inguinal adenopathy. Microscopic examination revealed biphasic tumors combining a poorly differentiated high-grade carcinoma with a poorly differentiated neuroblastic component lacking signs of proliferation. Immunohistochemical investigation revealed keratin 20 and MCPyV T antigen (TA) in the MCC parts, while neuroblastic differentiation was confirmed in the other component in both cases. A clonal relation of the two components can be deduced from 20 and 14 shared acquired point mutations detected by whole exome analysis in both combined tumors, respectively. Spatial transcriptomics demonstrated a lower expression of stem cell marker genes such as SOX2 and MCM2 in the neuroblastic component. Interestingly, although the neuroblastic part lacked TA expression, the same genomic MCPyV integration and the same large T-truncating mutations were observed in both tumor parts. Given that neuronal transdifferentiation upon TA repression has been reported for MCC cell lines, the most likely scenario for the two combined MCC/neuroblastic tumors is that neuroblastic transdifferentiation resulted from loss of TA expression in a subset of MCC cells. Indeed, DNA methylation profiling suggests an MCC-typical cellular origin for the combined MCC/neuroblastomas. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Clinicopathological characteristic of ciliated muconodular papillary tumour of the lung.

AIMS: Ciliated muconodular papillary tumour (CMPT) is a rare tumour characterised by tripartite cellular components of mucinous cells, ciliated columnar cells and basal cells with a predominantly papillary architecture. Its clinicopathological characteristics and treatment methods have not been fully elucidated. METHODS: Twenty-six patients with CMPT diagnosed and treated in our hospital were retrospectively analysed. RESULTS: The cohort was composed of 13 males and 13 females, with a mean age of 64.4±5.93 years. The diameter of the primary tumour ranged from 0.3 to 1.4 cm. The lesions appeared as subsolid nodules, ground-glass nodules and cavitary nodules under the CT scan. All the patients underwent surgical treatment and did not receive postoperative adjuvant therapy. All the CMPTs were diagnosed by immunohistochemistry and not by intraoperative frozen sections. Next-generation sequencing detection demonstrated EGFR, KRAS and BRAF mutations and ALK rearrangements in CMPTs. The follow-up duration ranged from 5 to 65 months, and no case of tumour recurrence was observed until the final follow-up. CONCLUSIONS: The incidence of CMPT is low, and the prognosis is good. Immunohistochemistry is helpful for an accurate diagnosis of CMPT, while intraoperative frozen sections cannot fully guide the surgical method. Sublobectomy may be enough without adjuvant treatment. CMPTs exhibited a relatively high rate of driver gene mutations, while the mutation sites were not consistent with those in lung adenocarcinoma.

Case report: composite pancreatic intraductal papillary mucinous neoplasm and neuroendocrine tumor: a new mixed neuroendocrine-non-neuroendocrine neoplasm?

BACKGROUND: Mixed neuroendocrine-non-neuroendocrine neoplasms (MiNEN) of the pancreas are extremely rare. Their pathogenesis and molecular landscape are largely unknown. Here, we report a case of mixed pancreatic intraductal papillary mucinous neoplasm (IPMN) and well-differentiated neuroendocrine tumor (NET) and identify its genetic alterations by next-generation sequencing (NGS). CASE PRESENTATION: A fifty-year-old male was admitted into the hospital for evaluation of a pancreatic lesion detected during a routine examination. Abdominal ultrasound indicated a hypoechoic mass of 2.6 cm at the head of the pancreas. Malignancy was suspected and partial pancreatectomy was performed. Thorough histopathological examination revealed a mixed IPMN-NET. In some areas, the two components were relatively separated, whereas in other areas IPMN and NET grew in a composite pattern: The papillae were lined with epithelial cells of IPMN, and there were clusters of NET nests in the stroma of papillary axis. NGS revealed shared somatic mutations (KRAS, PCK1, MLL3) in both components. The patient has been uneventful 21 months after the surgery. CONCLUSIONS: Our case provides evidence of a common origin for mixed IPMN-NET with composite growth features. Our result and literature review indicate that KRAS mutation might be a driver event underlying the occurrence of MiNEN. We also recommend the inclusion of mixed non-invasive exocrine neoplasms and neuroendocrine neoplasms into MiNEN.

Gene expression microarray analysis of adult testicular germ cell tumor: a comparison between pure-type seminomas and seminoma components in mixed tumors.

We previously demonstrated a genetic evidence of the progression from seminoma to embryonal carcinoma in mixed testicular germ cell tumors (TGCTs). This process, the "reprogramming" of seminoma cells, is crucial for pathological tumorigenesis and should be kept in mind while designing clinical therapeutic strategies. We hypothesized that a comparison between pure-type seminomas and seminoma components in mixed tumors (mixed-type seminomas) could reveal early changes in the reprogramming process. In the present study, we performed gene expression microarray analysis of six pure-type and six mixed-type seminomas. Hierarchical clustering analysis properly grouped each type of seminomas into a separated cluster. Supervised analysis between pure-type and mixed-type seminomas revealed 154 significantly dysregulated genes (Storey-adjusted q < 0.05). The genes with the highest overexpression in mixed-type seminomas compared with the pure-type seminomas included MT1 isoforms, PRSS8, TSC22D1, and SLC39A4; downregulated genes included DEFB123, LMTK2, and MYRF. Functional annotation analysis of the differentially expressed genes revealed that the top-ranked functional categories were related to cellular zinc metabolism and consisted of MT1 isoforms and SLC39A4, the results of which were validated using quantitative polymerase chain reaction and immunohistochemical analysis. In conclusion, this research provides further evidence that pure and mixed types of seminomas are molecularly different, which may contribute to elucidate the reprogramming mechanism in the progression of TGCTs.

Mixed phenotype acute leukemia in a child associated with a NUP98-NSD1 fusion and NRAS p.Gly61Arg mutation.

BACKGROUND: Mixed phenotype acute leukemia (MPAL) is a rare subset of acute leukemia in the pediatric population associated with genetic alterations seen in both acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). CASE: We describe a patient with MPAL with a NUP98 (nucleoporin 98)-NSD1 gene fusion (nuclear receptor binding SET domain protein1) and NRAS (neuroblastoma RAS viral oncogene homolog mutation) p.Gly61Arg mutation who was treated with upfront AML-based chemotherapy, received hematopoietic stem cell transplant (HSCT), but unfortunately died from relapsed disease. CONCLUSION: This case highlights the challenges faced in choosing treatment options in MPAL patients with complex genomics, with predominant myeloid features.

DNA mismatch repair deficiency and p53 abnormality are age-related events in mixed endometrial carcinoma with a clear cell component.

Mixed endometrial carcinoma (MEC) is defined as a tumor composed of two or more spatially distinct subtypes, at least one of which is serous or clear cell carcinoma. In this study, the clinicopathological features of 15 MEC cases containing a clear cell component (MEC-C) were investigated. The ages of patients ranged from 32 to 83 years (median, 61 years). The combinations of carcinoma components observed were endometrioid and clear cell in ten patients; endometrioid, clear cell and serous in three; and clear cell and serous in two. Immunohistochemically, nine had DNA mismatch repair (MMR) protein deficiency (MMR-d), nine had loss of ARID1A and three cases had aberrant p53 expression. MMR-d and loss of ARID1A showed a strong correlation. Only one case showed both MMR-d and aberrant p53 expression. The patients with MMR-d were younger than those without MMR-d (median; 58 years vs. 71 years). Loss of ARID1A also showed significant predilection for younger women than ARID1A intact cases. In conclusion, MMR-d was observed in 60 % of MEC-C, showed predilection for young women, and was associated with ARID1A loss. In contrast, non- MMR-d MEC-C occurred in elder women and some tumors may associate with TP53 mutation. These findings suggest that MEC-C develop via two different molecular mechanisms and they are age-related events.

Parotid Salivary Duct Carcinoma With a Prominent Squamous Component: Immunohistochemical Profile, Diagnostic Pitfalls, and Therapeutic Implications.

Salivary duct carcinoma of the parotid gland is a highly aggressive epithelial malignancy morphologically resembling high-grade, invasive, and in situ breast carcinoma. It can occasionally present with variable morphology making it diagnostically challenging in cases with unusual morphological components. Ancillary testing, particularly androgen receptor (AR) positivity on immunohistochemistry, can be very helpful in cases that demonstrate extensive squamous morphology, since AR positivity is uncommon in both the primary salivary gland and metastatic squamous cell carcinomas to the parotid. In this report, we describe a case of salivary duct carcinoma that showed only a squamous cell carcinoma component on the initial primary tumor site biopsy, as well as in subsequent contralateral neck lymph node and skin metastases. Apart from the variable morphology, the typical salivary duct and squamous cell carcinoma tumor components also showed significant immunohistochemical differences, including differential staining of human epidermal growth factor receptor 2/neu. The associated diagnostic pitfalls, distinct immunoprofiles of the tumor components, helpful adjuncts for making the correct diagnosis, and associated therapeutic implications are discussed.

Comprehensive genetic features of gastric mixed adenoneuroendocrine carcinomas and pure neuroendocrine carcinomas.

We aimed to determine the pathogenesis of gastric mixed adenoneuroendocrine carcinoma (MANEC) and pure neuroendocrine carcinoma (NEC), which is largely unknown. Targeted DNA sequencing was performed on 34 tumor samples from 21 patients - 13 adenocarcinoma (ADC)/NEC components from MANECs and eight pure NECs - and 21 matched non-neoplastic gastric tissues. Mutational profiles of MANECs/NECs were compared with those of other tumors using public databases. The majority (64.1%; 59/92) of mutations in MANEC were shared by both ADC and NEC components. TP53 was the most commonly mutated gene in MANEC (69.2%, 9/13) and pure NEC (87.5%, 8/9). All TP53 mutations in MANEC were pathogenic mutations and were shared by both ADC and NEC components. A subset of TP53WT MANECs had a microsatellite-unstable phenotype or amplifications in various oncogenes including ERBB2 and NMYC, and the only TP53WT pure NEC harbored MYC amplification. Compared to NEC in other organs, NECs arising from the stomach had unique features including less frequent RB1 mutations. Differentially altered genes of MANEC ADC components were significantly associated with receptor tyrosine kinase signaling pathways, while differentially altered genes of MANEC NEC components were significantly associated with the NOTCH signaling pathway. Our data provide evidence suggesting a possible clonal origin of ADC and NEC components of MANEC, and we found that gastric MANECs and pure NECs are distinct entities with unique mutational profiles and underlying protein networks. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Sex Cord Tumor With Annular Tubules-Like Histologic Pattern in Adult Granulosa Cell Tumor: Case Report of a Hitherto Unreported Morphologic Variant.

Adult granulosa cell tumor (AGCT) and sex cord tumor with annular tubules (SCTAT) are distinct sex cord stromal tumors with different molecular signatures. We present a unique case of an incidental ovarian tumor with mixed AGCT and SCTAT morphologic patterns. Due to the unusual co-occurrence, molecular testing was separately performed on both components. Despite minimal overlap in morphology, both the SCTAT and AGCT components were found to have an identical mutation profile, including the prototypical FOXL2 p.C134W mutation characteristic of AGCT. We thus present the first report of AGCT with SCTAT-like pattern.

Coexisting well-differentiated and anaplastic thyroid carcinoma in the same primary resection specimen: immunophenotypic and genetic comparison of the two components in a consecutive series of 13 cases and a review of the literature.

Anaplastic carcinoma (AC) is a rare but highly aggressive form of thyroid cancer. It mostly arises on a background of pre-existing well-differentiated cancer (WDC); however, whether it evolves directly from a WDC or originates as a second independent neoplasm is still to be defined. To obtain further insights into these mechanisms, we performed morphological, immunohistochemical, and next-generation sequencing analyses to compare AC and its associated WDC in a subset of 13 surgically resected specimens. Histologically, most WDC were of aggressive subtypes. Papillary carcinomas (8 cases; 62%) were tall cell (4/8), columnar (1/8), classic with hobnail features (1/8), classic and follicular variant in the remaining 2 cases; Hürthle cell and follicular carcinomas were present in 5 (38%) and in 1 (8%) patient, respectively. One patient harbored both a PTC, follicular variant, and a Hürthle cell carcinoma. We did not find any correlation between a histotype of WDC and a specific anaplastic growth pattern. Immunohistochemically, ACs retained pankeratin/PAX8 expression but with significantly lower levels than WDCs, and they tended to lose TTF1 expression, as can be expected within a dedifferentiation process. In addition, AC showed a more frequent expression of p63 and/or SMA, a mutated pattern of p53, and an abnormal expression of p16. Genetic analysis showed that the number of mutations was higher in AC than in the associated WDC, confirming a role of the progressive accumulation of genetic damage in this transition. We observed that mutations found in the WDCs were consistently identified in the anaplastic counterparts, further supporting the hypothesis of a developmental link.

Role of SMARCA4 (BRG1) and SMARCB1 (INI1) in Dedifferentiated Endometrial Carcinoma With Paradoxical Aberrant Expression of MMR in the Well-Differentiated Component: A Case Report and Review of the Literature.

INTRODUCTION: Dedifferentiated endometrial carcinoma is an uncommon highly aggressive uterine tumor. It comprises 2 components: a well-differentiated, low-grade epithelial carcinoma and an undifferentiated carcinoma. The undifferentiated carcinoma frequently exhibits rhabdoid cytologic features. Many of these tumors are characterized by an aberrant switch/sucrose non-fermenting (SWI/SNF) complex. They may also exhibit aberrant expression of mismatch repair (MMR) proteins. Together, these play an important role in the pathogenesis and aggressive nature of the tumor. MATERIAL AND METHODS: We present a case of dedifferentiated endometrial carcinoma in a 63-year-old female showing loss of expression of SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4 (SMARCA4/BRG1), and aberrant expression of MMR proteins. We also review the literature starting from the earliest recognition of this entity and the various studies done to explain its molecular pathogenesis and prognostic importance. RESULTS AND CONCLUSIONS: Recognition of SWI/SNF complex-deficient dedifferentiated endometrial carcinoma is important as these tumors do not respond to platinum-based chemotherapy, and consideration of alternative therapies is often necessary. We also want to emphasize that though most of the studies have found MMR deficiency in the undifferentiated carcinoma component, it may be seen only in the low-grade, well-differentiated component, as observed in this case.

Mixed large cell neuroendocrine carcinoma and squamous cell carcinoma of the colon: detailed molecular characterisation of two cases indicates a distinct colorectal cancer entity.

We present two rare cases of mixed large cell neuroendocrine carcinoma and squamous cell carcinoma of the colon. A literature search revealed only three published cases with similar histology but none of these reports provided profound molecular and mutational analyses. Our two cases exhibited a distinct, colon-like immunophenotype with strong nuclear CDX2 and ß-catenin expression in more than 90% of the tumour cells of both components. We analysed the two carcinomas regarding microsatellite stability, RAS, BRAF and PD-L1 status. In addition, next-generation panel sequencing with Ion AmpliSeq™ Cancer Hotspot Panel v2 was performed. This approach revealed mutations in FBXW7, CTNNB1 and PIK3CA in the first case and FBXW7 and RB1 mutations in the second case. We looked for similar mutational patterns in three publicly available colorectal adenocarcinoma data sets, as well as in collections of colorectal mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) and colorectal neuroendocrine carcinomas. This approach indicated that the FBXW7 point mutation, without being accompanied by classical adenoma-carcinoma sequence mutations, such as APC, KRAS and TP53, likely occurs at a relatively high frequency in mixed neuroendocrine and squamous cell carcinoma and therefore may be characteristic for this rare tumour type. FBXW7 codifies the substrate recognition element of an ubiquitin ligase, and inactivating FBXW7 mutations lead to an exceptional accumulation of its target ß-catenin which results in overactivation of the Wnt-signalling pathway. In line with previously described hypotheses of de-differentiation of colon cells by enhanced Wnt-signalling, our data indicate a crucial role for mutant FBXW7 in the unusual morphological switch that determines these rare neoplasms. Therefore, mixed large cell neuroendocrine and a squamous cell carcinoma can be considered as a distinct carcinoma entity in the colon, defined by morphology, immunophenotype and distinct molecular genetic alteration(s).

Pineal teratoma with nephroblastic component in a newborn male: Case report and review of the literature.

Neonatal germ cell tumors are rare and comprise both benign and malignant neoplasms. Teratoma with nephroblastoma is a malignant subset defined pathologically by the presence of nephroblastoma and teratoma elements. Although teratoma with nephroblastoma is most often found in the kidney, 24 of 59 reported cases are associated with extrarenal locations, such as the mediastinum or retroperitoneum. To our knowledge, this is the first patient in the literature with intracranial/pineal teratoma with nephroblastoma, which was managed with staged transcranial approaches resulting in gross total resection and no adjuvant therapy (surveillance observation imaging). We further augmented the patient's management by comprehensive genomic profiling of the tumor to better understand the molecular biology and explore options for targeted therapy.

Molecular Profiles of Mixed Endometrial Carcinoma.

Mixed endometrial carcinomas are defined as a combination of 2 or more distinct histologic subtypes, one of which must be a type II tumor comprising at least 5% of the tumor volume. The oncogenesis of these tumors remains unclear, particularly in light of the increasingly appreciated morphologic overlap among subtypes, as well as evolving molecular data. We evaluated 8 cases of mixed endometrial carcinoma, including 4 endometrioid (EC)/serous (SC), 1 SC/clear cell (CC), and 3 EC/CC cases, to study the underlying molecular features and oncogenic mechanisms at play. Each component was analyzed by a targeted next-generation sequencing assay. All tumors shared mutations in both components. In 6 cases, one component showed additional mutations. Two EC/SC cases showed shared mutations and mutations unique to each component. When present, unique mutations were typically seen in the SC component, including variants in POLE and TP53, as well as potentially targetable genes DDR2, MAP2K1, and CCNE1. In EC/SC tumors, ERBB2 abnormalities were seen in 2 cases. EC/CC cases showed FGFR2 activating mutations in the EC component only. No fusion drivers were identified. Our data suggest that the majority of these tumors begin as a single clone and diverge along 2 pathways: (1) tumor progression, with one component showing additional mutations, and (2) tumor divergence, in which tumor components have both shared mutations and mutations unique to each component. In addition, the findings suggest a component of morphologic mimicry in these tumors. Our findings are clinically relevant since targetable mutations may be present in only one component of mixed tumors.

Malignant tumours of the uterus and ovaries with Mullerian and germ cell or trophoblastic components have a somatic origin and are characterised by genomic instability.

AIMS: Tumours of the female genital tract with a combination of malignant Mullerian and germ cell or trophoblastic tumour (MMGC/T) components are usually diagnosed in postmenopausal women, and pursue an aggressive clinical course characterised by poor response to therapy and early relapses. These clinical features suggest that MMGC/T are somatic in origin, but objective molecular data to support this interpretation are lacking. This study evaluates the molecular features of nine MMGC/T, including seven tumours containing yolk sac tumour (YST), one tumour containing choriocarcinoma and one tumour containing epithelioid trophoblastic tumour. The objectives were to: (i) investigate whether MMGC/T show a distinct genetic profile and (ii) explore the relationship between the different histological components. METHODS AND RESULTS: Next-generation sequencing of paired samples demonstrated that the mutational profile of the Mullerian and non-Mullerian components of the tumour were almost identical in all cases. Moreover, the driver mutations identified were those expected in the specific subtype of Mullerian component present in each case. In contrast, variants expected in postpubertal germ cell tumours and gestational trophoblastic tumours were not identified, and FISH for i(12p) was negative in all cases tested. In this study, mismatch repair-proficient MMGC/T (eight of nine) were characterised by a complex copy-number variant profile, including numerous focal, regional, arm-level and chromosome-level events. CONCLUSIONS: Comparison of paired samples supports that the YST and trophoblastic tumour components of MMGC/T have a somatic origin and often show numerous copy-number variants, suggestive of underlying genomic instability.

Mixed adenoneuroendocrine carcinoma of the gallbladder, amphicrine type: Case report and review of literature.

Amphicrine type mixed adenoneuroendocrine carcinoma (MANEC), also known as amphicrine carcinoma, is an exceedingly rare neoplasm comprising of tumor cells simultaneously demonstrating both neuroendocrine and exocrine differentiation. Majority of reported cases were found in tubular gastrointestinal tracts such as colon. Herein, we report the first case of amphicrine carcinoma in gallbladder in a 57-year-old female who presented with abdominal pain, vomiting, and gallbladder mass on imaging followed by radical cholecystectomy. Macroscopically, the tumor was a polypoid solid mass with a firm and tan-white cut surface located at the gallbladder fundus. Histologically, the tumor cells were composed of monotonous-appearing signet-ring cells with fine chromatin, variably conspicuous nucleoli, brisk mitotic figures, and spotty necrosis. They were loosely clustered, forming nests and cords but no glandular formation. Immunohistochemically, the entire tumor showed strong and diffuse immunoreactivity for CDX2, p53, and synaptophysin, with patchy positivity for CD56, chromogranin, and INSM1. Kreyberg stain highlighted both intracytoplasmic and extracellular mucin. Ki-67 proliferation index was approximately 70%. Next-generation sequencing performed on a 724 cancer-related gene panel identified TP53 mutation at c.844C>T (p.R282W). To our knowledge, this is the first case of amphicrine carcinoma in gallbladder. It highlights the complex dynamism and controversial pathogenesis of this unique entity, the exact mechanism and clinicopathologic behavior of which are not yet understood.

Chromosomal and molecular pathway alterations in the neuroendocrine carcinoma and adenocarcinoma components of gastric mixed neuroendocrine-nonneuroendocrine neoplasm.

Gastric mixed adenoneuroendocrine carcinoma (MANEC) is a clinically aggressive subtype of mixed neuroendocrine-nonneuroendocrine neoplasm (MiNEN) with unclear clonal origin. In this study, we analyzed high-resolution copy number (CN) profiling data using the OncoScan CNV Assay in the neuroendocrine carcinoma (NEC) and adenocarcinoma components of eight MANECs. Some common CNVs, including the gain of CCNE1 (19q12) and the loss of FAT1 (4q35.2), were frequently detected in both components; these CNVs were verified by FISH, qPCR and immunohistochemistry staining assays in samples with sufficient material. The identification of common CNVs in both components supports the likelihood of single clonal origin of morphologically heterogeneous tumor cells and suggests several novel genetic events potentially involved in the development of gastric MANEC. We also detected and validated some CNVs and alterations specific for the NEC component, such as MAPK1 loss and MAPK signaling pathway alterations, which could contribute to the neuroendocrine differentiation of gastric MANEC. In addition, we found that the NEC component presented more CNVs and greater CN loss than the adenocarcinoma component (P = 0.007 and P = 0.004, respectively); the NEC components from different cases were not clustered in the hierarchical clustering analysis, indicating the marked genetic heterogenicity of the NEC component in gastric MANEC. In summary, this study describes the cytogenetic characteristics of each component of gastric MANEC, providing some clues for further studies on the development and progression of gastric MANEC as well as providing some potential therapeutic targets.

Stemness regulation of the adrenal mixed corticomedullary tumorigenesis-a case-control study.

Mixed corticomedullary tumor is an adrenal tumor intermixed with cortical and medullary cells. It is extremely rare with unclear tumorigenesis. We reported a 32-year-old female, manifested with typical Cushing's syndrome and hypertension, to be diagnosed with right huge adrenal mixed corticomedullary tumor (8.8 cm). Right adrenalectomy was done to document the tumor intimately admixed with adrenal cortical adenoma and pheochromocytoma by biochemistry and immunohistochemistry. A case-control study was designed to explore the tumorigenesis of mixed corticomedullary tumor by whole exome sequencing. Expression of the stemness markers was controlled by a tissue array of 80 adrenal tumors. Overall, 1559 identical variants coexisted in parts of adrenal cortical adenoma and pheochromocytoma, which mainly (85.8%) originated from germline mutations. These enriched mutations were engaged in stemness control, coherent with substantial expression of the stemness markers (SOX2, CD44 and OCT4) in both parts. The differential stemness expressions were demonstrated in other adrenal tumors as well. The germline mutations were also enriched in signaling involving cancer proliferation, hypoxia inducible factor-1, focal adhesion and extracellular matrix receptor interaction. Somatic mutations affecting mitogen-activated protein kinase signaling, glycolysis and the citrate cycle were found in some tumor elements. This is the first study to verify the rare mixed corticomedullary tumor by molecular and genetic evidence to link with its phenotype. Germline mutations involving the stemness regulation and cancer proliferative signaling may drive intermixed tumor formation. Somatic mutations related to glycolysis and the citrate cycle may contribute to greater tumor outgrowth.

The Immunosuppressive Niche of Soft-Tissue Sarcomas is Sustained by Tumor-Associated Macrophages and Characterized by Intratumoral Tertiary Lymphoid Structures.

PURPOSE: Clinical trials with immune checkpoint inhibition in sarcomas have demonstrated minimal response. Here, we interrogated the tumor microenvironment (TME) of two contrasting soft-tissue sarcomas (STS), rhabdomyosarcomas and undifferentiated pleomorphic sarcomas (UPS), with differing genetic underpinnings and responses to immune checkpoint inhibition to understand the mechanisms that lead to response. EXPERIMENTAL DESIGN: Utilizing fresh and formalin-fixed, paraffin-embedded tissue from patients diagnosed with UPS and rhabdomyosarcomas, we dissected the TME by using IHC, flow cytometry, and comparative transcriptomic studies. RESULTS: Our results demonstrated both STS subtypes to be dominated by tumor-associated macrophages and infiltrated with immune cells that localized near the tumor vasculature. Both subtypes had similar T-cell densities, however, their in situ distribution diverged. UPS specimens demonstrated diffuse intratumoral infiltration of T cells, while rhabdomyosarcomas samples revealed intratumoral T cells that clustered with B cells near perivascular beds, forming tertiary lymphoid structures (TLS). T cells in UPS specimens were comprised of abundant CD8+ T cells exhibiting high PD-1 expression, which might represent the tumor reactive repertoire. In rhabdomyosarcomas, T cells were limited to TLS, but expressed immune checkpoints and immunomodulatory molecules which, if appropriately targeted, could help unleash T cells into the rest of the tumor tissue. CONCLUSIONS: Our work in STS revealed an immunosuppressive TME dominated by myeloid cells, which may be overcome with activation of T cells that traffic into the tumor. In rhabdomyosarcomas, targeting T cells found within TLS may be key to achieve antitumor response.