Intraductal carcinoma of the salivary gland with NCOA4-RET: expanding the morphologic spectrum and an algorithmic diagnostic approach

Targeted RNA sequencing in diagnostically challenging head and neck carcinomas identifies novel MON2::STAT6, NFATC2::NUTM2B, POC5::RAF1, and NSD3::NCOA2 gene fusions

AIMS

Although molecular tests developed for a growing list of oncogenic alterations have significantly aided in the classification of head and neck carcinomas, tumours in which prototypical histologic and immunophenotypic features are lacking or only partially developed continue to pose diagnostic challenges. Searching for known diagnostic and therapeutic targets by clinical next-generation sequencing (NGS) assays can often lead to new discoveries.

METHODS AND RESULTS

We present our institutional experience in applying targeted RNA NGS in 36 head and neck carcinomas that were morphologically difficult to classify between 2016 and 2023. The patients ranged in age from 5 to 83 years (median, 64), with the majority of tumors occurring in the major salivary glands and the sinonasal tract. Overall, seven (19%) cases showed unusual gene rearrangements, including five novel alterations: MON2::STAT6 in a hard palate adenocarcinoma with mucinous features, POC5::RAF1 in apocrine intraductal carcinoma of the lacrimal gland, EWSR1::CDADC1 fusion in a basaloid carcinoma of the submandibular gland, NFATC2::NUTM2B in myoepithelial carcinoma, and NSD3::NCOA2 fusion in a peculiar high-grade carcinoma with a peritheliomatous growth pattern, and focal myogenic differentiation. Potential therapeutic actionability was identified in three cases (RAF1 and FGFR2 fusions).

CONCLUSION

These findings broaden the current spectrum of gene rearrangements in head and neck carcinomas and support the utility of clinical NGS in identifying unusual, actionable alterations in diagnostically challenging cases.

Intraductal carcinoma of the parotid gland, mixed intercalated duct and oncocytic subtype with mucinous and serous acinar differentiation: cytologic and histologic features of a novel morphology

Intraductal carcinoma (IDC) of the salivary gland is rare. Histologic subtypes include intercalated duct, oncocytic, apocrine, and hybrid/mixed. Molecular correlates have been described, with intercalated duct IDC typically harboring NCOA4::RET, while TRIM33::RET, or BRAFV600E pathogenic variants predominating in oncocytic IDC. We describe the case of a 77-year-old female with a parotid mass. Fine needle aspiration showed a population of low-grade epithelial cells with frequent cytoplasmic vacuolization, which were positive for S-100, SOX-10, and mammaglobin, and was interpreted as compatible with secretory carcinoma. A dual cell population was recognized on surgical resection, predominantly oncocytic, with at least one focus prototypical of intercalated IDC. Luminal secretions were positive for mucicarmine, while PAS after diastase highlighted the latter in addition to zymogen-like cytoplasmic granules. RNA sequencing detected a NCOA4::RET fusion. This is the first report of the cyto-histologic features of the mixed intercalated duct and oncocytic subtype IDC with mucous and serous acinar-like differentiation.

Clinicopathological, Prognostic and Molecular Profile of Salivary Gland Intraductal Carcinoma: A Systematic Review

PURPOSE

This study aimed to conduct a systematic review summarizing the clinicopathological, prognostic, and molecular features of salivary gland intraductal carcinoma (SGIC).

METHODS

This study followed the PRISMA 2020 guidelines and was registered in the PROSPERO database. It included case reports, case series studies, and cohort studies of SGIC indexed in the PubMed, Web of Science, Scopus, and Embase databases published between 1983 and 2024. Collected variables underwent descriptive analysis, association analysis using Fisher's tests, and Kaplan-Meier analysis. The quality assessment of the included studies was conducted using the Joanna Briggs Institute tools.

RESULTS

This systematic review yielded 59 studies, comprising 186 SGIC cases. Most of cases involved the parotid gland of male patients around 60 years old. Lesions predominantly exhibited noninvasive growth, an intercalated duct phenotype, and minimal pleomorphism. Most of the patients did not develop recurrent or metastatic disease, indicating a good prognosis. However, male sex, invasive lesions, adjuvant treatments, high-grade lesions, as well as lymph node or distant metastasis negatively affected the survival rates. Overall SGIC cases showed S100, mammaglobin, SOX10, AR, CK7, p63, calponin, CK14, SMA, and p40 positivity and a low Ki67 index. Common molecular alterations included NCOA4-RET, TRIM33-RET, and TRIM27-RET fusions, and HRAS, PIK3CA, and BRAF V600E mutations.

CONCLUSION

SGIC is a histopathologically and molecularly heterogeneous lesion with an overall excellent prognosis. The presence of invasive lesions, as well as lymph node or distant metastasis, has emerged as one of the most critical prognostic factors in SGIC patients.

Bronchial Sialadenoma Papilliferum in a 10-Year-Old Boy

Sialadenoma papilliferum (SP) is a rare salivary gland tumor mostly reported in the oral cavity. Here we describe a bronchial SP in the left upper lobe bronchus of a 10-year-old boy. At bronchoscopy, a well-circumscribed polypoid lesion protruding into the bronchial lumen was identified. The tumor was excised, but eventually, the patient had to undergo a sleeve resection after 2 recurrences. Pathology revealed a papillocystic lesion with exophytic and endophytic components. The cells lining the exophytic surface and papillary structures were columnar and squamous, and the cells lining endophytic cystic and papillary structures were cuboidal to columnar, all of which were diffusely reactive with antibodies to SOX10 protein. The presence of basal cells was demonstrated by p63 immunoreactivity. The cells failed to immunohistochemically express BRAF V600E. Fluorescence in situ hybridization analysis revealed no MAML2 or RET gene rearrangement. The patient is alive 24 years after resection with no additional recurrences. Bronchial SP needs to be recognized and distinguished from other benign and malignant salivary gland and pulmonary neoplasms so that patients can receive appropriate treatment and follow-up.

Salivary Gland Intraductal Carcinoma: How Do 183 Reported Cases Fit Into a Developing Classification

Salivary gland intraductal carcinoma (IDC) is a very uncommon group of neoplasms. Many names, variations in diagnostic criteria, and newly observed molecular findings (including NCOA4 :: RET , TRIM27 :: RET , HRAS point mutations, and PIK3CA pathway alterations) have generated further confusion in being able to recognize and categorize this group of tumors. Different histologic appearances and patterns of growth suggest there is more than one tumor category, with intercalated duct, apocrine, oncocytic, and hybrid features seen. Frankly destructive invasion further complicates the category, as the name "intraductal" would suggest an "in situ" neoplasm. Recent evidence on fusion-positive IDC demonstrates the same molecular underpinnings in both the ductal and the myoepithelial cells, which aids in further separating these tumors. This article summarizes the historical group of 183 neoplasms classified under the umbrella of IDC and highlights the unique histologic, immunohistochemistry, and molecular features that may further guide nomenclature standardization and harmonization.

Bronchial salivary gland–type intraductal carcinoma with KIAA1217::RET gene fusion composed of intercalated and oncocytic components

Salivary gland-type intraductal carcinoma (IC) is a rare malignant salivary gland neoplasm. Primary salivary gland-type IC has never been described in the lung. Herein, we present a primary pulmonary IC in a 63-year-old woman. The tumor originated in the bronchus wall of the right middle lobe. The tumor consisted of two histological types, intercalated component and oncocytic component. The intercalated component showed tubular/cystic pattern composed of column to cube-shaped cells and scattered mucous cells. The oncocytic component showed solid nests composed of large cells with abundant eosinophilic granular cytoplasm. Immunohistochemically, both histological components were positive for cytokeratin 7 (CK7), S-100 protein, SOX10, and mammaglobin. The rimming myoepithelial cells were highlighted by p63 and smooth muscle actin (SMA). The tumor cells were negative for androgen receptor (AR), HER-2, Dog-1, TTF-1, napsin A, GCDFP-15, and GATA3. In the present case, we detected KIAA1217::RET fusion via DNA-based next-generation sequencing (NGS) and RT-PCR, which established the diagnosis of IC at a molecular level. The present case expands the categories of bronchopulmonary salivary gland-type tumors.

RET signaling pathway and RET inhibitors in human cancer

Rearranged during transfection (RET) receptor tyrosine kinase was first identified over thirty years ago as a novel transforming gene. Since its discovery and subsequent pathway characterization, RET alterations have been identified in numerous cancer types and are most prevalent in thyroid carcinomas and non-small cell lung cancer (NSCLC). In other tumor types such as breast cancer and salivary gland carcinomas, RET alterations can be found at lower frequencies. Aberrant RET activity is associated with poor prognosis of thyroid and lung carcinoma patients, and is strongly correlated with increased risk of distant metastases. RET aberrations encompass a variety of genomic or proteomic alterations, most of which confer constitutive activation of RET. Activating RET alterations, such as point mutations or gene fusions, enhance activity of signaling pathways downstream of RET, namely PI3K/AKT, RAS/RAF, MAPK, and PLCγ pathways, to promote cell proliferation, growth, and survival. Given the important role that mutant RET plays in metastatic cancers, significant efforts have been made in developing inhibitors against RET kinase activity. These efforts have led to FDA approval of Selpercatinib and Pralsetinib for NSCLC, as well as, additional selective RET inhibitors in preclinical and clinical testing. This review covers the current biological understanding of RET signaling, the impact of RET hyperactivity on tumor progression in multiple tumor types, and RET inhibitors with promising preclinical and clinical efficacy.

Frankly Invasive Carcinoma Ex-intraductal Carcinoma: Expanding on an Emerging and Perplexing Concept in Salivary Gland Tumor Pathology

Intraductal carcinoma (IDC) of the salivary glands is an uncommon and enigmatic tumor, our understanding of which is rapidly evolving. Recent studies have demonstrated multiple IDC subtypes and consistent gene fusions, most frequently involving RET. Because IDC is a ductal proliferation surrounded by flattened myoepithelial cells, it was previously presumed to be analogous to breast ductal carcinoma in situ, but recent evidence has shown that the myoepithelial cells of fusion-positive IDC harbor the same genetic alterations of the ductal cells and are therefore neoplastic. In addition, there are rare reports of fusion-positive IDC with overt areas of irregular invasion lacking myoepithelial cells, but this phenomenon is not well documented or understood. This study aims to better characterize these frankly invasive carcinoma ex-IDC. All cases of frankly invasive carcinoma ex-IDC were obtained from the authors' files. Inclusion criteria included a component of concurrent or antecedent IDC and/or a fusion known to be associated with IDC. Immunohistochemistry (S100, SOX10, mammaglobin, androgen receptor, p63, p40) and molecular analysis (targeted RNA sequencing or large panel DNA next generation sequencing) was performed. Clinical follow-up was obtained from medical records. Ten cases of frankly invasive carcinoma ex-IDC were identified. The tumors occurred in 8 men and 2 women ranging from 33 to 82 years (mean, 66.3). All but one case arose in the parotid gland. In 4 cases, the IDC component was intercalated duct type. It was mixed apocrine/intercalated duct in two, and in the remaining 4 cases, no residual IDC was identified. The frankly invasive carcinomas were remarkably heterogeneous, ranging from minimally to widely invasive beyond the confines of the IDC, low-grade to high-grade, with morphologies that varied from duct-forming to those having clear cell or sarcomatoid features, to frankly apocrine. The original diagnoses for these cases were (adeno) carcinoma, not otherwise specified (n = 6), salivary duct carcinoma (n = 3), and secretory carcinoma (n = 1). All cases harbored fusions: NCOA4::RET (n = 6), TRIM33::RET (n = 2), TRIM27::RET (n = 1), and STRN::ALK (n = 1). Clinically, one tumor recurred locally, cervical lymph node metastases occurred in five patients, and distant metastasis later developed in four of these patients. Our findings highlight striking diversity in frankly invasive carcinomas that arise from fusion-positive IDC, a tumor which may serve as a precursor neoplasm like pleomorphic adenoma. These carcinomas vary in their extent of invasion, grade, histologic appearances, and clinical behavior. Importantly, in contrast to pure IDC, which is believed to be indolent, many frankly invasive cases were aggressive. Because RET and ALK fusions are targetable, it is important to recognize the broad spectrum of frankly invasive carcinomas that can arise from IDC, particularly because some cases are completely overrun or recur without any recognizable IDC component. These results suggest fusion analysis may be of clinical benefit on any salivary gland (adeno) carcinoma, not otherwise specified or salivary duct carcinoma.

Cytomorphologic features of intraductal salivary gland carcinoma: A multi-institutional study of 13 FNA cases with histologic, molecular, and clinical correlations

BACKGROUND

Intraductal carcinoma of the salivary gland (IDC) is a rare cancer with potential actionable targets, including RET fusions. Histologic and molecular features of IDC were recently reported, but cytomorphologic data are limited. In the largest multi-institutional fine-needle aspiration (FNA) series, the authors describe the cytomorphologic features of 13 IDC cases with available clinical, radiologic, histopathologic, and molecular data.

METHODS

The cases included 13 FNAs for 9 low-grade (LG) IDCs and 4 high-grade (HG) IDCs with corresponding histopathology and available molecular, imaging, and clinical data. Smears and liquid-based preparations available for 12 FNAs were semiquantitatively scored for key cytomorphologic findings and correlated with the corresponding resection.

RESULTS

LG IDC FNAs showed a cellular, biphasic population of large, atypical ductal cells with mildly pleomorphic nuclei in a clean background and a minor population of small, uniform myoepithelial cells. In contrast, all HG IDC FNAs showed predominantly ductal cells with marked nuclear pleomorphism, coarse chromatin, and necrosis. With the Milan system, most LG and HG IDC FNAs were classified as either salivary gland neoplasms of uncertain malignant potential (54%) or malignant (31%). Immunohistochemistry showed ductal epithelial reactivity with mammaglobin, androgen receptor, and S100, whereas myoepithelial cells were positive for p63 and/or calponin. Among cases with next-generation sequencing, 4 LG IDCs showed NCOA4-RET gene fusions, whereas an HG IDC showed HRAS and PIK3CA mutations.

CONCLUSIONS

The cytomorphology of IDC overlaps with other benign and malignant salivary gland neoplasms. Immunohistochemistry limits the differential diagnosis, but definitive classification requires molecular analysis. A diagnosis of IDC has potential implications for patient management.