DEK::AFF2 Fusion Carcinomas of Head and Neck

Molecularly defined sinonasal malignancies: an overview with focus on the current WHO classification and recently described provisional entities

Classification of tumors of the head and neck has evolved in recent decades including a widespread application of molecular testing in tumors of the sinonasal tract, salivary glands, and soft tissues with a predilection for the head and neck. The availability of new molecular techniques has allowed for the definition of multiple novel tumor types unique to head and neck sites. Moreover, an expanding spectrum of immunohistochemical markers specific to genetic alterations facilitates rapid identification of diagnostic molecular abnormalities. As such, it is currently possible for head and neck pathologists to benefit from a molecularly defined tumor classification while making diagnoses that are still based largely on histopathology and immunohistochemistry. This review covers the principal molecular alterations in sinonasal malignancies, such as alterations in DEK, AFF2, NUTM1, IDH1-2, and SWI/SNF genes in particular, that are important from a practical standpoint for diagnosis, prognosis, and prediction of response to treatment.

[Translocated sinonasal tumors]

In recent years, several nasal cavity and sinus entities have been described with fusion genes. Salivary gland tumors with fusion genes will not be discussed in this article, but it should be kept in mind that accessory salivary glands are present in the nasal cavity and sinuses and can therefore lead to tumoral lesions. Entities with specific or more frequently described rearrangements in the nasal cavities and sinuses are DEK::AFF2 squamous cell carcinomas,;non-intestinal and non-salivary nasosinusal adenocarcinomas, some of which displaying ETV6 gene rearrangements; biphenotypic nasosinusal sarcomas, most of which displaying PAX3 gene rearrangements; and Ewing's adamantinoma-like sarcomas, which display the same rearrangements as conventional Ewing's sarcomas, mainly the EWSR1::FLI1 rearrangement. Each entity will be described morphologically, immunohistochemically, and prognostically.

Top IHC/ISH Hacks for and Molecular Surrogates of Poorly Differentiated Sinonasal Small Round Cell Tumors

BACKGROUND

Poorly differentiated sinonasal small round cell tumors (SRCTs) are rare and heterogeneous, posing challenges in diagnosis and treatment.

METHODS

Recent advances in molecular findings and diagnostic refinement have promoted better understanding and management of these tumors.

RESULTS

The newly defined and emerging sinonasal entities demonstrate diverse morphologies, specific genomic signatures, and clinical behavior from conventional counterparts. In this review of SRCTs, emphasis is placed on the diagnostic approach with the employment of a pertinent panel of immunohistochemistry studies and/or molecular tests, fine-tuned to the latest WHO 5 classification of sinonasal/paranasal tumors and personalized treatment.

CONCLUSION

Specifically, this review focuses on tumors with epithelial and neuroectodermal derivation.

Prevalence and interpretation of AFF immunostain of DEK::AFF2 fusion-associated papillary squamous cell carcinoma in a retrospective cohort of recurrent sinonasal papillomas

DEK::AFF2 fusion-associated papillary squamous cell carcinoma is a novel entity characterized by its unique translocation and malignant clinical course. In this study, AFF immunohistochemistry (IHC) was performed in recurrent sinonasal papillomas for reviewing the prevalence of undiagnosed DEK::AFF2 carcinomas and to investigate the performance of AFF IHC in diagnosis of DEK::AFF2 carcinomas. Recurrent sinonasal papillomas after surgical excision in a two-decade period were retrieved. Histologic slides were reviewed for features of DEK::AFF2 carcinoma. AFF IHC was performed, and cases with any (> 1%) nuclear positivity were validated by DEK break apart fluorescence in situ hybridization. Totally 43 cases were included, comprising 28 inverted, 6 exophytic, one oncocytic, and 8 non-specified sinonasal papillomas. Five (11.6%) cases exhibited positivity to AFF IHC. Three cases exhibited patchy weak to moderate staining intensity predominantly in a granular cytoplasmic pattern. Two cases exhibited strong and diffuse (> 90%) nuclear staining. Cases showing weak staining were negative for DEK rearrangement, while those with strong staining were positive. Both cases of DEK::AFF2 carcinoma showed aggressive behavior with extensive local invasion and nodal metastasis. Background stromal plasma cells, when present, consistently showed strong and diffuse staining. AFF IHC was further performed in plasmacytoma samples as control and showed strong and diffuse immunoreactivity. A significant minority of recurrent sinonasal papillomas represent DEK::AFF2 carcinomas. Granular, cytoplasmic, or incomplete AFF staining should be considered as negative. In view of the rarity of DEK::AFF2 carcinomas, plasma cells and plasma cell neoplasms are potential for internal and surrogate external controls.

A diagnostic algorithm for sinonasal papillary non-keratinizing squamous cell carcinoma with DEK::AFF2 fusion and mimickers

Sinonasal carcinomas represent a rare and diverse group of tumors, presenting diagnostic complexities due to their varied histological and molecular features. To ensure accurate differentiation among these malignancies, a systematic and stepwise approach is paramount. Even with the morphological similarities between poorly differentiated (non) keratinizing sinonasal squamous cell carcinoma (SNSCC) and DEK::AFF2 SNSCC, the two lesions are distinguishable using the surrogate immunohistochemical marker AFF2 or molecular testing for DEK::AFF2 mutation. We report a rare case of SMARCB1-retained DEK::AFF2 papillary non-keratinizing SNSCC in a 53-year-old female, who presented with a polypoid mass corresponding to the left middle turbinate. Following the surgical resection of the tumor and locoregional lymph nodes, adjuvant radiotherapy was administered to eradicate any residual cancer cells that may have remained after surgery.

The First Report of Cytology of DEK::AFF2 Fusion-Associated Papillary Squamous Cell Carcinoma on Fine-Needle Aspiration

DEK::AFF2 fusion-associated papillary squamous cell carcinoma is a recently characterized sinonasal malignancy defined by its unique translocation. DEK::AFF2 carcinomas may be deceptively monotonous and lack keratinization, resembling transitional epithelium. The lack of traditional cytological atypia presents diagnostic challenges. Our case describes the first report of fine-needle aspiration cytology of a lymph node involved by DEK::AFF2 carcinoma in a patient with previously resected sinonasal inverted papilloma with carcinomatous transformation six years prior to presentation. This aspirate consisted of a lymphoid-rich background admixed with a moderate amount of epithelial cells arranged in cohesive structures of variable size, including large sheets. The tumor cells resembled those of the corresponding biopsy, featuring mildly hyperchromatic nuclei with fine to vesicular chromatin. Lesional cells lacked keratinization, mitoses, or hyperchromasia. Our finding suggests that in nodal aspirates of patients with a history of sinonasal-type papillomas, especially those with prior malignant transformation or atypia, there should be consideration for the possibility of DEK::AFF2-related primary. When in doubt, DEK FISH of AFF2 immunohistochemistry should be performed for confirmation.

Sinonasal DEK-rearranged Papillary Non-keratinizing Squamous Cell Carcinoma: Expanding the Emerging Entity

The newly emerging sinonasal carcinomas have demonstrated diverse morphologies and specific molecular mutations along with deviant clinical behavior from conventional counterparts. Also, many sinonasal malignancies turned to be SMARCB1/SMARCA4-deficient. Even with the morphological similarities between poorly differentiated (non) keratinizing sinonasal squamous cell carcinoma (SNSCC) from DEK::AFF2 SNSCC, the two lesions are not distinguishable using the surrogate immunohistochemical marker AFF2 or molecular testing for DEK::AFF2 mutation. We report a rare case of SMARCB1-retained DEK-rearranged papillary non-keratinizing SNSCC in a 53-year-old female, who presented with a polypoid mass corresponding to the left middle turbinate. The tumor and locoregional lymph nodes were surgically resected, followed by adjuvant radiotherapy.

The screening, identification, design and clinical application of tumor-specific neoantigens for TCR-T cells

Recent advances in neoantigen research have accelerated the development of tumor immunotherapies, including adoptive cell therapies (ACTs), cancer vaccines and antibody-based therapies, particularly for solid tumors. With the development of next-generation sequencing and bioinformatics technology, the rapid identification and prediction of tumor-specific antigens (TSAs) has become possible. Compared with tumor-associated antigens (TAAs), highly immunogenic TSAs provide new targets for personalized tumor immunotherapy and can be used as prospective indicators for predicting tumor patient survival, prognosis, and immune checkpoint blockade response. Here, the identification and characterization of neoantigens and the clinical application of neoantigen-based TCR-T immunotherapy strategies are summarized, and the current status, inherent challenges, and clinical translational potential of these strategies are discussed.

The impact of the chromatin binding DEK protein in hematopoiesis and acute myeloid leukemia

Hematopoiesis is an exquisitely regulated process of cellular differentiation to create diverse cell types of the blood. Genetic mutations, or aberrant regulation of gene transcription, can interrupt normal hematopoiesis. This can have dire pathological consequences, including acute myeloid leukemia (AML), in which generation of the myeloid lineage of differentiated cells is interrupted. In this literature review, we discuss how the chromatin remodeling DEK protein can control hematopoietic stem cell quiescence, hematopoietic progenitor cell proliferation, and myelopoiesis. We further discuss the oncogenic consequences of the t(6;9) chromosomal translocation, which creates the DEK-NUP214 (aka: DEK-CAN) fusion gene, during the pathogenesis of AML. Combined, the literature indicates that DEK is crucial for maintaining homeostasis of hematopoietic stem and progenitor cells, including myeloid progenitors.

[Sinonasal neoplasms: Update from the WHO 2022]

The pathology of poorly differentiated sinonasal malignancies has undergone a dynamic evolution during the last decade, resulting in a refined, mostly genetically or etiologically oriented classification of neoplasms in the historical spectrum of sinonasal undifferentiated carcinoma (NUT carcinoma, SWI-/SNF-deficient carcinomas, and others). Moreover, some new entities have been established, while others could be further delineated and better characterized. A highlight of the new classification is the inclusion of SWI/SNF (SMARCB1 or SMARCA4)-deficient carcinomas into a separate category. In addition, carcinomas with DEK::AFF2 fusions have been included as a provisional entity in the spectrum of nonkeratinizing squamous cell carcinoma. This review addresses the major changes in the classification of sinonasal tract neoplasms in the new WHO classification.

Molecular Basis and Rationale for the Use of Targeted Agents and Immunotherapy in Sinonasal Cancers

Despite the progress of surgery, radiotherapy, and neoadjuvant chemotherapy, the prognosis for advanced sinonasal cancers (SNCs) remains poor. In the era of precision medicine, more research has been conducted on the molecular pathways and recurrent mutations of SNCs, with the aim of understanding carcinogenesis, helping with diagnosis, identifying prognostic factors, and finding potentially targetable mutations. In the treatment of SNC, immunotherapy is rarely used, and no targeted therapies have been approved, partly because these tumors are usually excluded from major clinical trials. Data on the efficacy of targeted agents and immune checkpoint inhibitors are scarce. Despite those issues, a tumor-agnostic treatment approach based on targeted drugs against a detected genetic mutation is growing in several settings and cancer subtypes, and could also be proposed for SNCs. Our work aims to provide an overview of the main molecular pathways altered in the different epithelial subtypes of sinonasal and skull base tumors, focusing on the possible actionable mutations for which potential target therapies are already approved in other cancer types.