SWI/SNF-deficient cancers of the Gastroenteropancreatic tract: an in-depth review of the literature and pathology

Delayed Diagnosis of SMARCA4-Deficient Undifferentiated Tumor in a Heavy Smoker Male Patient: Discovered Through Bone Sampling, with Extensive Distant Metastases and Concurrent Granulomatous Disease, Leading to Patient Fatality

Background. SMARCA4-deficient undifferentiated tumors are rare and pose a diagnostic challenge. This study delves into the intricate diagnostic terrain of SMARCA4-deficient undifferentiated tumors, providing insights into their diverse clinical presentations and diagnostic approaches. Case Presentation. A 69-year-old heavy-smoker man with adalimumab-treated rheumatoid arthritis presented with multiple lesions. A CT scan revealed a spiculated lung mass, enlarged mediastinal lymph nodes, and hepatic lesions. A whole-body FDG-PET/CT scan revealed heterogeneous hypermetabolic lesions in the lung, liver, and bone. Initial two core needle liver biopsies and a left upper lobe lung wedge resection initially indicated steatohepatitis and granulomatous formation with no evidence of malignancy. Several months later, the patient returned with left-sided flank pain and significant weight loss. CT scan identified a thigh mass, adrenal lesion, and extensive multiple skeletal lesions. A biopsy of the thigh mass revealed an extensively necrotic, epithelioid-to-spindled cell neoplasm with positive staining for pan keratin, focal staining for CD56, and a loss of nuclear expression of SMARCA4. A final diagnosis of SMARCA4-deficient undifferentiated tumor was rendered. Unfortunately, the patient's condition deteriorated, and he died a few weeks after receiving the final diagnosis. Conclusion. SMARCA4-deficient undifferentiated tumors have emerged as recent subjects of medical study, distinguished by their unique morphology and SMARCA4-deficient immunohistochemistry. These tumors present diverse clinical manifestations, affecting multiple organ systems. This report underscores the diagnostic complexities associated with complex clinical presentation and highlights the importance of multidisciplinary collaboration in addressing challenging clinical scenarios, particularly among heavy smoker male patients and intricate radiological presentations.

Colorectal Carcinoma With Sarcomatoid Components: Report of 15 Cases and Literature Review of an Exceedingly Rare Carcinoma Subtype

Colorectal carcinoma with sarcomatoid components (which includes so-called carcinosarcomas and sarcomatoid carcinomas) is a rare subtype with 50 reported cases in the literature and overlapping criteria with undifferentiated carcinoma. We collected and described 15 cases from 10 men and 5 women, with a mean age of 66 years. Symptoms included abdominal pain and gastrointestinal bleeding. Most tumors presented in the rectosigmoid region, with a mean size of 8.2 cm. The sarcomatoid component, on average, represented 58% of the tumors and took many forms, including spindled (10 cases), anaplastic (9 cases), and rhabdoid (3 cases); one case showed osteoid matrix. Tumor budding was usually high, and tumor-infiltrating lymphocytes were usually low. The sarcomatoid component was keratin-positive in 10 cases. One case showed loss of mismatch repair protein expression, and 2 cases showed SMARCA4 loss (1 also with SMARCA2 loss). Molecular testing identified mutations in KRAS (n=1), NRAS (n=2), BRAF (n=2), APC (n=1), and TP53 (n=1) in a few cases. Tumors often presented at advanced stage, with 11 cases pT4, 9 cases with nodal metastases, and 7 cases with distant metastases. Follow-up was available for 10 cases (median: 2 months), with 2 alive without disease, 3 alive with disease, and 5 dead. Our findings roughly corresponded with those in previously reported cases. Colorectal carcinoma with sarcomatoid components is rare and aggressive, with a poor prognosis for many patients. We suggest that spindled cells, anaplasia, heterologous elements, and/or a component with definable sarcomatous lineage be used to distinguish colorectal carcinoma with sarcomatoid components from undifferentiated carcinoma.

SMARCA4-Deficient Undifferentiated Tumor of the Esophagus: Diagnostic Pitfalls in Immunohistochemical Profiles

SMARCA4-deficient undifferentiated tumors (SMARCA4-UT) are a newly described entity and are typically seen in the thoracic cavity. However, these tumors have been described in other body sites, including the esophagus. These tumors are rare, aggressive neoplasms, characterized by the loss of protein product of SMARCA4 (Brahma-related gene-1) and the preservation of INI1 (SMARCB1) expression. Here, we present two tumors of SMARCA4-UT of the esophagus with its microscopic appearance and immunohistochemical profile. We also include a literature review of SMARCA4-deficient tumors of the tubular gastrointestinal tract with their immunohistochemical and mismatch repair profiles for each specimen. Due to its non-specific histologic appearance and variable staining in expanded immunohistochemical panels, this tumor frequently overlaps with other tumor types, making the diagnosis of SMARCA4-UT challenging. These tumors are often associated with intestinal metaplasia of the esophagus and are thought to represent a high-grade undifferentiated transformation of a conventional esophageal adenocarcinoma. These tumors are typically associated with poor clinical outcomes and have poor response to conventional therapies. Currently, there are no standard guidelines for treatment of these tumors; however, palliative radiotherapy and systemic chemotherapy may provide benefit. More recently, immunotherapy and novel therapeutic targets have shown some promise for these patients.

SMARCA4/BRG1-Deficient Sinonasal Carcinoma: Morphologic Spectrum of an Evolving Entity

CONTEXT.—

Molecular analysis of poorly differentiated/undifferentiated sinonasal neoplasms has resulted in identification of a growing number of genetically defined tumors. SMARCA4-deficient sinonasal carcinoma is one such recently described entity that emerged from within sinonasal undifferentiated carcinoma (SNUC), neuroendocrine carcinoma (NEC), and teratocarcinosarcoma (TCS).

OBJECTIVE.—

To identify SMARCA4-deficient sinonasal carcinomas from a large institutional cohort of poorly differentiated/undifferentiated carcinomas and evaluate their clinicopathologic features.

DESIGN.—

SMARCA4/BRG1 immunohistochemistry was performed on all tumors diagnosed as SNUC, poorly differentiated carcinoma, NEC, and TCS during a 12-year period. SMARCA2/BRM and INSM1 immunostaining was performed in SMARCA4-deficient cases.

RESULTS.—

Twelve SMARCA4-deficient sinonasal carcinomas were identified among 299 cases. Morphologically, 5 cases were large cell NEC, 2 cases were small cell NEC, and 5 were TCS. SMARCA4 loss was diffuse and complete in 10 cases, while 2 cases showed focal retention. Most cases showed diffuse cytokeratin staining accompanied by weak, usually focal staining for chromogranin and synaptophysin. INSM-1 showed negativity in most cases. All cases showed retained SMARCA2 expression. IDH1/2 mutation was absent in all cases analyzed. Four of 7 patients died of disease, and aggressive multimodality treatment had better outcome.

CONCLUSIONS.—

SMARCA4-deficient sinonasal carcinomas are morphologically akin to sinonasal poorly differentiated NECs and TCS, display cytokeratin positivity and only focal staining for neuroendocrine markers, and have aggressive biological behavior. Inclusion of SMARCA4 in the immunohistochemical panel for diagnostic workup of all sinonasal NEC and TCS phenotypes will facilitate their early recognition. Comprehensive germline and somatic mutational analyses of these tumors are necessary for further insights into their molecular pathogenesis.

Immunohistochemistry as predictive and prognostic markers for gastrointestinal malignancies

Biomarkers play a key role in the comprehensive pathologic evaluation of gastrointestinal malignancies. These biomarkers can be predictive, indicating whether a tumor is likely to respond to a particular therapy, or prognostic, providing information about the likely course and outcome of a disease. This review article will discuss available immunohistochemical stains for assessing these markers, including staining rationale, scoring criteria, associated systemic therapies, and pictorial examples. PD-L1, HER2, and mismatch repair status can be evaluated via immunohistochemistry for esophageal, gastric, and colorectal carcinomas. Biomarkers currently play a more limited role in evaluation of pancreatic and small bowel malignancies. Immunohistochemistry can also be used to evaluate biomarker status in gastrointestinal stromal tumors, gastrointestinal malignancies with NTRK gene fusions, and undifferentiated carcinomas with switch-sucrose non-fermentable complex abnormalities.

Recent updates in thoracic SMARCA4-deficient undifferentiated tumor

Germline inactivating mutations in SMARCA4 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4) gene encoding for BRG1 (Brahma related gene-1) are the molecular drivers in small cell carcinoma of ovary, hypercalcemic type (SCCOHT) and in malignant rhabdoid tumors (MRT) that occur in the context of rhabdoid tumor predisposition syndrome-type 2. Somatic SMARCA4 mutations and/or loss of BRG1 have been identified in a variety of adult-onset epithelial and mesenchymal neoplasms. Among thoracic tumors, these include subsets of smoking-related non-small cell lung carcinoma (NSCLC) and a relatively rare, newly recognised tumor entity: thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT). Less than 100 cases of SMARCA4-UT have been reported to date. They present as large compressive and infiltrative mediastinal, lung and/or pleural masses in middle-aged male smokers. They are undifferentiated tumors composed of sheets of small/epithelioid and/or rhabdoid tumor cells variably expressing epithelial markers and consistently showing loss of BRG1 and the closely related protein, Brahma (BRM). Frequent expression of stem cell markers (SOX2, CD34, SALL4) is noted. Despite gene expression profiles similar to MRTs and SCCOHT, they show striking genomic overlap with SMARCA4-mutant NSCLC with frequent TP53, STK11, KEAP1, and KRAS mutations, high tumor mutation burden (TMB), and presence of smoking related molecular signatures in tumor cells. SMARCA4-UT show uniformly poor survival and are irresponsive to conventional therapies. Immunotherapy responses are variable but promising, although PDL1 expression appears to be of poor predictive value. Drugs exploiting genetic and epigenetic mechanisms of SMARCA4 antagonism hold promise for future targeted therapies.