Molecular characterization of dedifferentiated mucoepidermoid carcinoma of the trachea using laser microdissection-basedTP53mutation analysis

High-Grade Transformation and Carcinosarcoma: A Review of Two Forms of Advanced Progression in the Salivary Gland

CONTEXT.—

High-grade transformation, previously known as dedifferentiation, in salivary gland carcinoma and carcinosarcoma ex pleomorphic adenoma is a rare phenomenon. It is, however, clinically relevant and affects treatment and prognosis.

OBJECTIVE.—

To review the existing literature, describe the histologic and immunophenotypic features, and highlight the diagnostic criteria of high-grade transformation in various salivary gland carcinomas and carcinosarcomas; to review its effect on clinical presentation and prognosis; and to review relevant molecular characteristics and recent concepts and advances.

DATA SOURCES.—

Literature search in PubMed using key words such as "high-grade transformation," "dedifferentiation," and "carcinosarcoma" in salivary gland. Relevant articles were reviewed, and additional articles were curated from the references of these articles.

CONCLUSIONS.—

High-grade transformation occurs rarely but has a significant impact on prognosis and management. By microscopy, the high-grade area is usually a distinct nodule and shows solid and nested architecture, cellular atypia, high mitotic count, and necrosis. The molecular features are not well established. Carcinosarcoma almost always arises in a pleomorphic adenoma and likely follows an adenoma-carcinoma-sarcoma pathway.

The Challenge of "Monomorphic" Mucoepidermoid Carcinoma-Report of a Rare Case with Pure Spindle-Clear Cell Morphology

BACKGROUND

Mucoepidermoid carcinoma is a malignant salivary gland tumor which, in most cases, is composed of variable proportions of mucous, epidermoid, and intermediate cells.

METHODS

We report a case of parapharyngeal mucoepidermoid carcinoma with highly unusual ("monomorphic") light microscopic features as well as atypical immunohistochemical properties. Molecular analysis was performed using the TruSight RNA fusion panel.

RESULTS

The tumor featured heretofore undescribed histopathological features: sheets and nests composed of monomorphic neoplastic (plump spindle to epithelioid) cells with no mucous, intermediate, glandular/columnar, or any other cell type identified. The neoplastic cells displayed variable clear cell change and only expressed cytokeratin 7. Despite this non-classical morphology, the presence of the classical CRTC1::MAML2 fusion was demonstrated.

CONCLUSIONS

Mucoepidermoid carcinoma featuring a uniform ("monomorphic") population of neoplastic cells is a novel observation. A confident diagnosis of mucoepidermoid carcinoma can be made upon detection of the CRTC1/3::MAML2 fusion. Our case increases the spectrum of histopathological appearances that mucoepidermoid carcinoma may display.

Clinicopathological and molecular study of 10 salivary gland clear cell carcinomas, with emphasis on rare cases with high grade transformation and occurring in uncommon sites

Background

As a rare salivary gland malignancy, clear cell carcinoma (CCC) is easily misdiagnosed. This study identified the features that allow better recognition of the clinicopathological and molecular characteristics and the prognosis of CCC, focusing on high-grade transformation (HGT) in this tumor and cases arising in uncommon sites.

Methods

Clinicopathological and follow-up data for 10 CCC samples were retrieved. Immunohistochemical (IHC) staining was performed, and fluorescence in situ hybridization (FISH) was used to detect EWSR1 gene rearrangements, EWSR1–ATF1 gene fusions, and MAML2 gene rearrangements.

Results

Histologically, typical CCCs comprised bland polygonal or round cells with clear cytoplasm. In contrast with typical CCCs, HGT tumor cells exhibited nuclear pleomorphism, high nuclear-to-cytoplasmic ratios, high mitotic activity, and necrosis. Rare morphologic features such as pseudopapillae, gland-like spaces, and entrapped ducts were also observed. Occasionally, tumors involving the oral cavity might arise from the overlying epithelium of the mucosal surface. Immunohistochemically, all the cases expressed p63, p40, and CK5/6, while myoepithelial-related markers were uniformly negative in all cases. HGT exhibited a wild type p53 expression pattern. FISH demonstrated EWSR1 rearrangement (10/10) and EWSR1–ATF1 fusion (4/5); however, MAML2 remained intact (0/3).

Conclusions

CCCs with HGT or occurring in uncommon sites are extremely rare. Combining morphology based IHC and molecular detection provided reliable evidence that the HGT component represented a transformation of CCC rather than the coexistence of another tumor and helped differentiating CCCs in uncommon sites from their mimics, avoiding potential misdiagnosis and inappropriate therapy. The overall prognosis for CCCs is good, except for the HGT cases, which needed continued treatment.

Undifferentiated and dedifferentiated head and neck carcinomas

Undifferentiated carcinomas arising at salivary gland and head and neck mucosal sites may originate either de novo or through a process of dedifferentiation of a differentiated carcinoma. While in the latter group the diagnosis is largely dependent on the identification of the differentiated component or recognition of a specific genotype, the classification of undifferentiated carcinomas that lack a differentiated component is mainly based on the identification of specific genetic drivers, like for example the NUTM1 fusions in NUT carcinoma. A further category is represented by virus associated carcinomas (mainly HPV and EBV), that frequently displays an undifferentiated morphology. Overall, these tumors often represent a diagnostic challenge, especially in small biopsies. This review summarizes and discuss the diagnostic approach to the main head and neck carcinoma types that frequently or occasionally display an undifferentiated appearance, with a focus on salivary gland, oropharyngeal, nasopharyngeal and sinonasal subsites.

High-grade Transformation/Dedifferentiation in Salivary Gland Carcinomas: Occurrence Across Subtypes and Clinical Significance

High-grade transformation (HGT) or dedifferentiation has been described in a variety of salivary gland carcinomas, including acinic cell carcinoma, secretory carcinoma, adenoid cystic carcinoma, epithelial-myoepithelial carcinoma, polymorphous adenocarcinoma, low-grade mucoepidermoid carcinoma, and hyalinizing clear cell carcinoma. High-grade (HG) transformed tumors are composed of a conventional low-grade component characterized by specific microscopic and immunohistochemical features for the given entity, intermingled with or juxtaposed to areas of HG morphology. This is usually either poorly differentiated adenocarcinoma, carcinoma not otherwise specified, or undifferentiated carcinoma, in which the original line of differentiation is lost. The HG component is composed of solid nests of anaplastic cells with large vesicular pleomorphic nuclei, prominent nucleoli, and abundant cytoplasm. Frequent mitoses and extensive necrosis may be present. The Ki-67 labeling index is consistently higher in the HG component. The molecular genetic mechanisms responsible for HGT of salivary gland carcinomas are largely unknown, though p53 inactivation and human epidermal growth factor receptor 2 overexpression and/or gene amplification have been demonstrated in the HG component in a few examples, the frequency varies for each histologic type. Salivary gland carcinomas with HGT are more aggressive than conventional carcinomas, with a higher local recurrence rate and a poorer prognosis. They have a high propensity for cervical lymph node metastasis suggesting a need for a wider resection and neck dissection. HGT of salivary gland carcinoma can occur either at initial presentation or less commonly at the time of recurrence, sometimes following postoperative radiotherapy. The potential for HGT in almost any type of salivary gland carcinoma warrants a thorough sampling of all salivary gland malignancies to prevent oversight of a HG component.

Dedifferentiated secretory breast carcinoma with fibrosarcomatous features harboring an ETV6-NTRK3 fusion in both components

Secretory carcinomas are low-grade translocation-driven carcinomas occurring in patients over a wide age range. These tumors most frequently arise in the breast and salivary gland, but may occasionally arise at other anatomic sites, such as the skin, the thyroid gland or the upper or lower respiratory tract. In concert with their low-grade morphology, secretory carcinomas most often follow an indolent clinical course. However, rare cases have shown dedifferentiation (also known as high-grade transformation) and aggressive clinical behavior. To date, the dedifferentiated component in all molecularly confirmed cases of secretory carcinoma has taken the form of a high-grade carcinoma. Here we present a case of an ETV6-NTRK3 fusion-positive secretory carcinoma of the breast with sarcomatous dedifferentiation. The sarcomatous component showed an infantile or adult fibrosarcoma-like morphology including a herringbone fascicular pattern and a hemangiopericytic vascular pattern. By immunohistochemistry, the sarcomatous component showed focal CD34 immunoreactivity and loss of all of the markers expressed in the conventional secretory carcinoma component, including SOX10, S100, GATA-3, AE1/AE3 and E-cadherin. Fluorescence in situ hybridization analysis revealed that the sarcomatous component retained the ETV6-NTRK3 fusion, but also acquired homozygous deletion of CDKN2A. The tumor followed an aggressive clinical course and the patient eventually succumbed to her disease 14 months after diagnosis. The histomorphologic and molecular genetic features of this tumor are discussed, including its ability to mimic kinase-rearranged infantile or adult fibrosarcomas at extramammary sites and the theragnostic importance of its distinction from conventional metaplastic spindle cell carcinomas in the breast.

High Grade Transformation in Mucoepidermoid Carcinoma of the Minor Salivary Gland with Polyploidy of the Rearranged MAML2 Gene

Mucoepidermoid carcinoma (MEC) is the most common malignant tumor of the salivary gland. However, reports of high grade transformation in MEC are extremely rare, and only two cases have so far been described. Recent development of salivary gland pathology revealed recurrent gene rearrangements in many kinds of tumors, including MAML2 fusion of MEC. To date, the MAML2 status of high grade transformed MEC has not been studied. Here we report the first case of minor salivary gland origin high grade transformation in MEC with a MAML2 break apart FISH study. A 73-year-old woman presented with a 1-month history of left mandibular area swelling, and computed tomography and magnetic resonance imaging revealed a mass in the hard palate with various-sized lymphadenopathy of the neck. The resected tumor histologically consisted of two carcinomatous components. Approximately 30% of the tumor showed a conventional MEC feature, while 70% was comprised of a high grade transformed component. In the conventional MEC component, FISH revealed MAML2 rearrangement. High grade transformed cells showed multiple split signals, and the results were interpreted as rearrangement and polyploidy after comparison with 1p/19q FISH as validation. The patient received adjuvant radiation therapy after wide resection with neck dissection and retropharyngeal dissection. Nevertheless, as the remaining tumor grew up rapidly and metastatic lymph nodes were newly revealed, the patient expired 7 months after the diagnosis. We first report regarding a high grade transformation in MEC with polyploidy of the rearranged MAML2 gene and aggressive biological behavior.

Salivary gland hybrid tumour revisited: could they represent high-grade transformation in a low-grade neoplasm?

Salivary gland hybrid tumour, first described in 1996, is a very rare neoplasm for which exact morphological criteria have not been universally agreed upon. In contrast, the concept of high-grade transformation (HGT) in salivary neoplasms has been widely accepted during the last decade, and the number of reported cases is rapidly increasing. A review of the literature revealed 38 cases of hybrid tumour reported in 22 publications. During approximately the same time period, well over 100 cases of HGT in salivary neoplasms have been reported. There are important histological similarities between hybrid tumours and salivary tumours with HGT. In the latter, containing one tumour component of low-grade malignancy and the other of high grade, the two tumour components are not entirely separated and appear to originate in the same area. Virtually, all cases reported as hybrid tumour had no clear lines of demarcation between the two tumour types. We are inclined to suggest that most of the 38 cases of hybrid tumours described in the literature would today better be called tumour with HGT rather than hybrid tumour. The relative proportion of the two components may vary, and the high-grade component is sometimes very small, which emphasises the importance of very generous sampling of the surgical specimen. The molecular genetic mechanisms responsible for HGT, including what used to be called hybrid tumour, remain largely unknown. Abnormalities of a few genes (including p53, C-MYC, cyclin D1, HER-2/neu) have been documented. As insufficient data exist on gene abnormalities in these lesions, conclusions as to whether or not they have a common origin and which mechanisms are involved in transformation cannot be drawn. Due to the small number of cases reported, many of which lack follow-up details; indicators of prognosis of hybrid tumours are not available, but their behaviour seems to be similar to that of tumours with HGT, i.e. an accelerated aggressive course. HGT of salivary gland neoplasms greatly influences macroscopic and microscopic evaluation of the specimen but also, given the high incidence of metastases and morbidity, carries significant treatment implications.

High grade transformation of salivary gland acinic cell carcinoma with emphasis on histological diagnosis and clinical implications

Acinic cell carcinoma (ACC) is commonly thought of as a low grade malignant salivary neoplasm, and possibly has the best prognosis of all salivary malignancies with a 10-year survival of almost 90%. High grade transformation (HGT) in these tumours is a relatively rare event but is increasingly being reported. HGT (formerly referred to as dedifferentiation) in acinic cell carcinoma has shown to drastically reduce the survival rates and its recognition is imperative as more aggressive clinical management is needed. We report a case of parotid acinic cell carcinoma in a 82-year old woman where the fine needle aspirate suggested either pleomorphic adenoma or the possibility of carcinoma ex pleomorphic adenoma. Per-operatively it became clear that the facial nerve was involved and the tumour mass was debulked only. The histology showed an acinic cell carcinoma with foci of high grade differentiation (ACC-HGT). We describe the histology of HGT in ACC and the most common differential diagnoses. We emphasise the need of very generous sampling of the tumour, as to recognise any area of high grade transformation, some of which can be very small. A literature review of ACC-HGT as well as HGT in other salivary gland neoplasms is presented. HGT of ACC greatly thus influences the macroscopical and microscopical evaluation of the specimen but also, given the high incidence of metastases and morbidity, carries significant treatment implications.

Cervical Lymph Node Metastasis in High-Grade Transformation of Head and Neck Adenoid Cystic Carcinoma: A Collective International Review

Adenoid cystic carcinoma (AdCC) is among the most common malignant tumors of the salivary glands. It is characterized by a prolonged clinical course, with frequent local recurrences, late onset of metastases and fatal outcome. High-grade transformation (HGT) is an uncommon phenomenon among salivary carcinomas and is associated with increased tumor aggressiveness. In AdCC with high-grade transformation (AdCC–HGT), the clinical course deviates from the natural history of AdCC. It tends to be accelerated, with a high propensity for lymph node metastasis. In order to shed light on this rare event and, in particular, on treatment implications, we undertook this review: searching for all published cases of AdCC-HGT. We conclude that it is mandatory to perform elective neck dissection in patients with AdCC-HGT, due to the high risk of lymph node metastases associated with transformation.

"Dedifferentiation" and high-grade transformation in salivary gland carcinomas

"Dedifferentiation" and/or high-grade transformation (HGT) has been described in a variety of salivary gland carcinomas, including acinic cell carcinoma, adenoid cystic carcinoma, epithelial-myoepithelial carcinoma, polymorphous low-grade adenocarcinoma, myoepithelial carcinoma, low-grade mucoepidermoid carcinoma and hyalinizing clear cell carcinoma, although the phenomenon is a rare event. Recent authors tend to preferably use the term HGT instead of "dedifferentiation" in these cases. HGT-tumors are composed of conventional carcinomas juxtaposed with areas of HG morphology, usually either poorly differentiated adenocarcinoma or "undifferentiated" carcinoma, in which the original line of differentiation is no longer evident. The HG component is generally composed of solid nests, sometimes occurring in cribriform pattern of anaplastic cells with large vesicular pleomorphic nuclei, prominent nucleoli and abundant cytoplasm. Frequent mitoses and extensive necrosis is evident. The Ki-67 labeling index is consistently higher in the HG component. p53 abnormalities have been demonstrated in the transformed component in a few examples, but the frequency varies by the histologic type. HER-2/neu overexpression and/or gene amplification is considerably exceptional. The molecular-genetic mechanisms responsible for the pathway of HGT in salivary gland carcinomas largely still remain to be elucidated. Salivary gland carcinomas with HGT have been shown to be more aggressive than conventional carcinomas with a poorer prognosis, accompanied by higher local recurrence rate and propensity for cervical lymph node metastasis, suggesting the need for wider resection and neck dissection.

Myoepithelial carcinoma: first case reported in the trachea

Myoepithelial carcinoma displaying exclusively myoepithelial differentiation mainly occurs in the salivary glands and breasts, and is considered extremely rare in the trachea. We present the first documented case of a primary myoepithelial carcinoma in the trachea. The patient was a 23-year-old man who presented with shortness of breath and cough for four months. Bronchoscopy and computed tomographic (CT) scan revealed an intraluminal mass in the trachea. A standard sleeve of trachea resection with end-to-end reconstruction was performed. The tumor was mainly composed of spindle cells and epithelioid cells which exhibited relatively uniform nuclei with finely distributed chromatin and inconspicuous nucleoli, suggesting that it may arise from benign myoepithelioma. Moreover, the tumor displayed marked cytologic atypia and an infiltrative tumor border in some areas, suggesting that it was a malignant tumor. Immunohistochemically, the tumor cells were diffusely positive for AE1/AE3, Vimentin and myoepithelial makers (Calponin, P63 and GFAP). The patient's postoperative course was uneventful with no evidence of recurrence at six months after surgery.

Current concepts on dedifferentiation/high-grade transformation in salivary gland tumors

The concept of dedifferentiation had previously been used in salivary gland carcinomas. Recently, the term “high-grade transformation” was introduced for adenoid cystic carcinoma, acinic cell carcinoma, epithelial-myoepithelial carcinoma, and polymorphous low-grade adenocarcinoma and may better reflect this phenomenon, although transformation into moderately differentiated adenocarcinoma (i.e., not “high grade”) has also been described. Among the immunohistochemical markers, Ki-67 seems to be the only one that can help distinguish between the conventional and transformed components; however, the combination of morphological criteria is still sovereign. The overexpression of p53 was observed in the transformed component in all tumor types studied, despite few cases having been demonstrated to carry mutations or deletions in TP53 gene. Genetic studies in salivary gland tumors with dedifferentiation/high-grade transformation are rare and deserve further investigation. This paper aims at providing an overview on the recent concepts in histopathological classification of salivary gland tumors, complemented by immunohistochemical and genetic findings.

Anaplastic myoepithelial carcinoma of the sinonasal tract: an underrecognized salivary-type tumor among the sinonasal small round blue cell malignancies? Report of one case and a review of the literature

We present a 45 year old female patient with a nasal carcinoma showing high-grade/anaplastic histomorphological features and with a distinct myoepithelial immunohistochemical phenotype including positivity for smooth muscle actin, p63, S100 protein with no sustentacular pattern, calponin, cytokeratin 14, vimentin and cytokeratins (AE1-3 and CK5/6). A minority (<5%) of the cells showed focal and variable immunoreactivity for EMA with no cuticular/canalicular pattern. Bcl-2, CD99, CD117 and CD56 were variously positive, but chromogranin and synaptophysin were negative. Weak to moderate nuclear p53 immunoreactivity was seen in 50% of tumor cells. Mib-1/Ki-67 showed an average proliferation of 60-70%. Fluorescent in situ hybridization revealed no EWS-gene translocation. In situ hybridization for EBER was negative.