A panel-based approach using immunohistochemistry (IHC) is currently used for subtyping perianal Paget disease (PPD) in the absence of a synchronous neoplasm. Special AT-rich Sequence Binding Protein 2 (SATB2) has been established as a sensitive and specific marker for lower gastrointestinal tract carcinomas. We evaluated its performance as a marker of secondary PPD. A panel of IHCs including CK7, CK20, GCDFP-15, CDX2, and SATB2 were performed on fifteen cases of PPD (identified between 1991-2001) and seven cases of primary vulvar Paget disease with perianal involvement. Eight cases (53%) were classified as secondary PPD based on the presence of a synchronous (n = 7) or a metachronous neoplasm (n = 1). There was no differential staining for CK7 (positive in 7/7 primary vs. 7/8 secondary PPD; P = 1.00) and CK20 (positive in 4/7 primary vs. 8/8 secondary PPD; P = .08). GCDFP-15 was positive in 5/7 cases of primary PPD while negative in all cases of secondary PPD (P = .01). CDX2 was positive in all cases of secondary PPD (P = .001) while SATB2 was positive in 7/8 cases of secondary PPD (P = .01). Both CDX2 and SATB2 were positive in 1/7 cases of primary PPD. The addition of an IHC panel in conjunction with clinical/imaging findings can help definitively classify PPD as either primary or secondary in most cases. We show that SATB2 has comparable performance to CDX2 and can be a helpful additional tool.

Mammalian dentition exhibits distinct heterodonty, with more simple teeth located in the anterior area of the jaw and more complex teeth situated posteriorly. While some region-specific differences in signalling have been described previously, here we performed a comprehensive analysis of gene expression at the early stages of odontogenesis to obtain complete knowledge of the signalling pathways involved in early jaw patterning. Gene expression was analysed separately on anterior and posterior areas of the lower jaw at two early stages (E11.5 and E12.5) of odontogenesis. Gene expression profiling revealed distinct region-specific expression patterns in mouse mandibles, including several known BMP and FGF signalling members and we also identified several new molecules exhibiting significant differences in expression along the anterior-posterior axis, which potentially can play the role during incisor and molar specification. Next, we followed one of the anterior molecules, SATB2, which was expressed not only in the anterior mesenchyme where incisor germs are initiated, however, we uncovered a distinct SATB2-positive region in the mesenchyme closely surrounding molars. Satb2-deficient animals demonstrated defective incisor development confirming a crucial role of SATB2 in formation of anterior teeth. On the other hand, ectopic tooth germs were observed in the molar area indicating differential effect of Satb2-deficiency in individual jaw regions. In conclusion, our data provide a rich source of fundamental information, which can be used to determine molecular regulation driving early embryonic jaw patterning and serve for a deeper understanding of molecular signalling directed towards incisor and molar development.

BACKGROUND: It is known that the neurodevelopmental disorder associated gene, Satb2, plays important roles in determining the upper layer neuron specification. However, it is not well known how this gene regulates other neocortical regions during the development. It is also lack of comprehensive delineation of its spatially regulatory pathways in neocortical development.
RESULTS: In this work, we utilized spatial transcriptomics and immuno-staining to systematically investigate the region-specific gene regulation of Satb2 by comparing the Satb2+/+ and Satb2-/- mice at embryonic stages, including the ventricle zone (VZ) or subventricle zone (SVZ), intermediate zone (IZ) and cortical plate (CP) respectively. The staining result reveals that these three regions become moderately or significantly thinner in the Satb2-/- mice. In the cellular level, the cell number increases in the VZ/SVZ, whereas the cell number decreases in the CP. The spatial transcriptomics data show that many important genes and relevant pathways are dysregulated in Satb2-/- mice in a region-specific manner. In the VZ/SVZ, the key genes involved in neural precursor cell proliferation, including the intermediate progenitor marker Tbr2 and the lactate production related gene Ldha, are up-regulated in Satb2-/- mice. In the IZ, the key genes in regulating neuronal differentiation and migration, such as Rnd2, exhibit ectopic expressions in the Satb2-/- mice. In the CP, the lineage-specific genes, Tbr1 and Bcl11b, are abnormally expressed. The neuropeptide related gene Npy is down-regulated in Satb2-/- mice. Finally, we validated the abnormal expressions of key regulators by using immunofluorescence or qPCR.
CONCLUSIONS: In summary, our work provides insights on the region-specific genes and pathways which are regulated by Satb2 in neocortical development.

A number of immunohistochemical stains have been examined for utility in establishing the site of origin for metastatic well-differentiated neuroendocrine tumors (NETs). In the gastrointestinal (GI) tract, distinguishing metastatic duodenal NETs from jejunoileal and other GI NETs is important for clinical work-up, prognosis, and therapy. A recent study indicated that prohormone convertase 2 (PCSK2 or PC2) had broad expression in small intestine and appendiceal NETs. Because the study did not include duodenal NETs, we examined PCSK2 expression in duodenal and other GI NETs.
GI NETs (n = 69) and 13 corresponding lymph node metastases from stomach, duodenum, pancreas, ileum, appendix, and rectum were evaluated for the expression of PCSK2, along with ISL1, NKX2.2, CDX2, SATB2, and PAX8. Expression of each stain was evaluated using the H-score system, and differences in expression by site were evaluated by the chi square test.
PCSK2 was expressed at similar frequency in duodenal (50%), pancreatic (59%), and ileal NETs (40%). PCSK2 was infrequently expressed in stomach (0%), appendiceal (8%), and rectal (25%) NETs. However, incorporating PCSK2 into a panel including ISL1, NKX2.2, CDX2, and SATB2 allowed development of an algorithm which had 87% sensitivity and 93% specificity for classification of ileal NETs; and 68% sensitivity and 98% specificity for pancreaticoduodenal NETs.
In contrast to previous findings, PCSK2 does not show specificity for any particular GI site. An algorithmic approach incorporating the expression of PCSK2 with that of ISL1, NKX2.2, CDX2, and SATB2 is useful in discriminating pancreatic, duodenal, ileal, appendiceal, and rectal NETs.

BACKGROUND: The lungs are a common site of tumor metastasis. While morphology and immunophenotype can help differentiate primary from metastatic tumors, distinguishing pulmonary invasive mucinous adenocarcinoma (PIMA) from metastatic colorectal adenocarcinoma (CRC) may occasionally be challenging due to overlapping morphological and immunohistochemical features. Lineage-specific markers such as CDX2, TTF-1, and napsin A are helpful with pulmonary non-mucinous adenocarcinoma (PNMA), however they are non-specific and insensitive when applied to PIMA. SATB2 is a newer marker that distinguishes CRC from upper gastrointestinal and pancreaticobiliary tumors; its utility in distinguishing CRC from PIMA has not been fully elucidated.
OBJECTIVE: To evaluate the performance of lineage-specific and mucin glycoprotein immunostains in distinguishing PIMA and CRC.
METHODS: We stained tissue microarrays comprising 34 PNMA, 31 PIMA, and 32 CRC with CK7, CK20, SATB2, CDX2, villin, TTF-1, napsin A, and gel-forming mucins MUC2, MUC5AC, and MUC6.
RESULTS: PIMA showed significant (>50% of cells) expression of SATB2 (6%), CDX2 (6%), villin (74%), TTF-1 (13%), and napsin A (23%). However, significant CK7 expression was seen in nearly all PIMA (30/31) and none of the metastatic CRC.
CONCLUSIONS: Our results suggest that CK7 remains one of the most useful markers for distinguishing primary PIMA from metastatic CRC. Expression of the mucin glycoproteins MUC5AC and MUC6 and lack of expression of MUC2 favored a diagnosis of PIMA, but expression of these markers was too heterogeneous to be of clinical utility. To our knowledge this is the only study comparing the immunohistochemical profile of PIMA and metastatic CRC in lung metastasectomy specimens.

Accurate stratification of an ovarian mucinous neoplasm as primary or secondary is always challenging as they show overlapping histomorphological and immunohistochemical features. Immunohistochemical staining for SATB2 and PAX8 was performed on 80 cases of mucinous ovarian neoplasms subdivided into 53 primary [25 primary ovarian mucinous carcinomas (POMCs) and 28 mucinous borderline tumors (MBTs)] and 27 secondary (12 of colonic origin, 7 of appendiceal origin, and 8 of gastric origin). Expression was correlated with different clinicopathologic parameters. PAX8-positive immunostaining was detected in 38 out of 53 cases (71.69%) of primary ovarian mucinous neoplasms (POMNs) with null positivity in the secondary ovarian mucinous tumors (0/27). SATB2-positive expression was detected in 16 out of 27 cases (59.26%) of the secondary ovarian mucinous tumors. None of the studied POMNs showed any positive immunostaining for SATB2 (0/53). A profile of SATB2-/PAX8+ and SATB2+/PAX8- can be used to differentiate POMNCs from secondary ovarian mucinous tumors of GI origin, respectively, with 100% specificity. PAX8 expression is associated with some clinicopathologic parameters providing the basis for the possible usage of PAX8 as prognostic marker.

BACKGROUND: Glass syndrome, derived from chromosomal 2q33.1 microdeletions, manifests with intellectual disability, microcephaly, epilepsy, and distinctive features, including micrognathia, down-slanting palpebral fissures, cleft palate, and crowded teeth. Recently, SATB2 located within the deletion region, was identified as the causative gene responsible for Glass syndrome. Numerous disease-causing variants within the SATB2 coding region have been reported.
OBJECTIVE: Given the presentation of intellectual disability and multiple congenital anomalies in a patient with a de novo reciprocal translocation between chromosomes 1 and 2, disruption of the causative gene(s) was suspected. This study sought to identify the causative gene in the patient.
METHODS: Long-read whole-genome sequencing was performed, and the expression level of the candidate gene was analyzed.
RESULTS: The detection of breakpoints was successful. While the breakpoint on chromosome 1 disrupted RNF220, it was not deemed to be a genetic cause. Conversely, SATB2 is located in the approximately 100-kb telomeric region of the breakpoint on chromosome 2. The patient\'s clinical features resembled those of previously reported cases of Glass syndrome, despite the lack of confirmed reduced SATB2 expression.
CONCLUSIONS: The patient was diagnosed with Glass syndrome due to the similarity in clinical features. This led us to hypothesize that disruption in the downstream region of SATB2 could result in Glass syndrome. The microhomologies identified in the breakpoint junctions indicate a potential molecular mechanism involving microhomology-mediated break-induced repair mechanism or template switching.

Telangiectatic osteosarcoma (TOS) is a rare variant of osteosarcoma that typically affects young individuals and long bones. The case under discussion was seen in the mandible of a 57-year-old female and had rapidly grown in size within a week. Microscopically, the tumour was characterised by large vascular cavities surrounded by anaplastic cells. Thin lacy tumour osteoid was observed at various foci. Abundant multinucleated osteoclastic giant cells along with areas of necrosis were also noted. The tumour cells were positive for SATB2, while negative for Cytokeratin AE1/3, CD 34. Ki-67 positivity was observed in more than 50% of tumour cells. A diagnosis of high grade telangiectatic osteosarcoma was thus made.

Special AT-rich sequence binding protein-2 (SATB2) is a nuclear matrix protein that binds to nuclear attachment regions and is involved in chromatin remodeling and transcription regulation. In stem cells, it regulates the expression of genes required for maintaining pluripotency and self-renewal and epithelial-mesenchymal transition (EMT). In this study, we examined the oncogenic role of SATB2 in prostate cancer and assessed whether overexpression of SATB2 in human normal prostate epithelial cells (PrECs) induces properties of cancer stem cells (CSCs). The results demonstrate that SATB2 is highly expressed in prostate cancer cell lines and CSCs, but not in PrECs. Overexpression of SATB2 in PrECs induces cellular transformation which was evident by the formation of colonies in soft agar and spheroids in suspension. Overexpression of SATB2 in PrECs also resulted in induction of stem cell markers (CD44 and CD133), pluripotency-maintaining transcription factors (cMYC, OCT4, SOX2, KLF4, and NANOG), CADHERIN switch, and EMT-related transcription factors. Chromatin immunoprecipitation assay demonstrated that SATB2 can directly bind to promoters of BCL-2, BSP, NANOG, MYC, XIAP, KLF4, and HOXA2, suggesting SATB2 is capable of directly regulating pluripotency/self-renewal, cell survival, and proliferation. Since prostate CSCs play a crucial role in cancer initiation, progression, and metastasis, we also examined the effects of SATB2 knockdown on stemness. SATB2 knockdown in prostate CSCs inhibited spheroid formation, cell viability, colony formation, cell motility, migration, and invasion compared to their scrambled control groups. SATB2 knockdown in CSCs also upregulated the expression of E-CADHERIN and inhibited the expression of N-CADHERIN, SNAIL, SLUG, and ZEB1. The expression of SATB2 was significantly higher in prostate adenocarcinoma compared to normal tissues. Overall, our data suggest that SATB2 acts as an oncogenic factor where it is capable of inducing malignant changes in PrECs by inducing CSC characteristics.

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