Sinonasal Tract Alveolar Rhabdomyosarcoma in Adults: A Clinicopathologic and Immunophenotypic Study of Fifty-Two Cases with Emphasis on Epithelial Immunoreactivity

Management of head & neck sarcomas in adults: A retrospective study

The research purpose is to review the surgical approach and evaluate the results in adult patients with head and neck sarcomas. The histopathology varied, including two leiomyosarcomas, six malignant fibrous histiocytomas, two malignant peripheral nerve sheath tumors, four dermatofibrosarcomas protuberans, three osteosarcomas, two angiosarcomas, one liposarcoma, one Ewing sarcoma, one synovial sarcoma, two unclassified/non-differentiated sarcomas and one solitary fibrous tumor. Surgical resection included maxillectomy, mandibulectomy, craniectomy, parotidectomy, scalp resection, face skin resection and laminectomy. The reconstruction was performed with one rectus abdominis flap, four radial forearm flaps, two latissimus dorsi flaps, two vascularized fibula flaps, two pectoralis major myocutaneous flaps, two trapezius flaps, two temporalis flaps, seven scalp flaps and two nasolabial flaps. The total patient number was 24. The hospitalization was uncomplicated, followed by postoperative radiotherapy in the majority of cases. In a mean 15-year follow-up period, 11 patients are still alive and disease-free. There were four recurrences treated with palliative radiotherapy. The surgical approach for head and neck sarcomas, including the achievement of a functionally acceptable result by organ sparing techniques, remains challenging. Wide resection combined with the appropriate reconstruction, particularly with microsurgical techniques, and followed by adjuvant radiotherapy or chemotherapy offer improved prognosis and quality of life.

Small cell neuroendocrine carcinoma and poorly differentiated rhabdomyosarcomas of the urinary bladder in adults-A comparative analysis in favor of a common histogenesis

Rhabdomyosarcoma (RMS) of the urinary bladder in adults and elderly is an exceptionally rare neoplasm that displays poorly differentiated solid (alveolar-like) small cell pattern, frequently indistinguishable from small cell neuroendocrine carcinoma (SCNEC). However, the histogenesis of RMS and SCNEC and their inter-relationship have not been well studied and remained controversial. We herein analyzed 23 SCNEC and 3 small round cell RMS of the bladder for neuroendocrine (synaptophysin + chromogranin A) and myogenic (desmin + myogenin) marker expression and for TERT promoter mutations. In addition, the RMS cohort and one SCNEC that was revised to RMS were tested for gene fusions using targeted RNA sequencing (TruSight Illumina Panel which includes FOXO1 and most of RMS-related other genes). Overall, significant expression of myogenin and desmin was observed in one of 23 original SCNEC justifying a revised diagnosis to RMS. On the other hand, diffuse expression of synaptophysin was noted in 2 of the 4 RMS, but chromogranin A was not expressed in 3 RMS tested. TERT promoter mutations were detected in 15 of 22 (68%) SCNEC and in two of three (67%) assessable RMS cases, respectively. None of the four RMS cases had gene fusions. Our data highlights phenotypic and genetic overlap between SCNEC and RMS of the urinary bladder. High frequency of TERT promoter mutations in SCNEC is in line with their presumable urothelial origin. In addition, the presence of TERT promoter mutation in 2 of 3 RMS and lack of FOXO1 and other gene fusions in all 4 RMSs suggest a mucosal (urothelial) origin, probably representing extensive monomorphic rhabdomyoblastic transdifferentiation in SCNEC.

"Aberrant" expression of skeletal muscle markers in neuroendocrine carcinomas: a significant diagnostic pitfall

In this study, we investigate the expression of muscle markers, including the specific skeletal muscle markers myogenin and myoD1, in neuroendocrine carcinomas (NECs). The study included 23 NECs from various sites (14 small cell NECs and 9 large cell NECs). These were stained with desmin, myogenin and myoD1. Positive staining with at least one muscle marker was observed in 14 cases (61%). 8 (35%), 8 (35%) and 11 (48%) of the cases were positive with desmin, myogenin and myoD1 respectively. In most, but not all, cases positive staining was focal generally involving < 10% of tumour cells. Expression of muscle markers is not uncommon in NECs. This represents an important diagnostic pitfall of which pathologists should be aware. In reporting this phenomenon, we speculate on the pathogenesis of this "aberrant" expression of muscle markers.

Induction Chemotherapy Prior to Endoscopic Resection of Alveolar Rhabdomyosarcoma

Head and neck rhabdomyosarcoma (HNRMS) is a rare type of soft tissue tumor that affects both adults and children with an overall incidence of 0.041 per 100,000 people. Adults make up approximately 31.2% of all HNRMS diagnoses and have an overall survival rate between 20% and 40%. We present a case of a 46-year-old male who initially presented with nasal congestion and vision changes. Maxillofacial computed tomography and magnetic resonance imaging of the brain showed involvement of the orbital apex, abutment of the planum sphenoidale, and extension to the foramen rotundum (FR). Nasal endoscopy with biopsy confirmed the diagnosis of T2aN0M0 parameningeal HNRMS. The patient underwent induction chemotherapy, followed by endoscopic resection, which resulted in negative intraoperative margins. Subsequently, he underwent adjuvant concurrent chemotherapy and proton beam radiation after positive microscopic positive margins were found on the optic nerve. The patient did not experience any significant complications, and he is currently without radiographic or clinical recurrence 18 months after the treatment. He was able to maintain his vision throughout the treatment. In adults, HNRMS is usually treated with chemoradiotherapy based on pediatric protocols, since there are limited data available for adult treatment protocols and outcomes. Although surgery has been associated with positive outcomes in adult patients, there are no previous reports of its use with either neoadjuvant or adjuvant treatment. This type of treatment protocol has never been described for adult HNRMS. We hope that our report can add more data to the growing body of literature on HNRMS treatment protocols.

Pan-keratin Immunostaining in Human Tumors: A Tissue Microarray Study of 15,940 Tumors

To evaluate the efficiency of pan-keratin immunostaining, tissue microarrays of 13,501 tumor samples from 121 different tumor types and subtypes as well as 608 samples of 76 different normal tissue types were analyzed by immunohistochemistry. In normal tissues, strong pan-keratin immunostaining was seen in epithelial cells. Staining intensity was lower in hepatocytes, islets of Langerhans, and pneumocytes but markedly reduced in the adrenal cortex. Pan-keratin was positive in ≥98% of samples in 62 (83%) of 75 epithelial tumor entities, including almost all adenocarcinomas, squamous cell and urothelial carcinomas. Only 17 of 121 tumor entities (13%) had a pan-keratin positivity rate between 25% and 98%, including tumors with mixed differentiation, endocrine/neuroendocrine tumors, renal cell carcinomas, adrenocortical tumors, and particularly poorly differentiated carcinoma subtypes. The 15 entities with pan-keratin positivity in 0.9%-25% were mostly of mesenchymal origin. Reduced/absent pan-keratin immunostaining was associated with high UICC stage (p = 0.0001), high Thoenes grade (p = 0.0183), high Fuhrman grade (p = 0.0049), advanced tumor stage (p < 0.0001) and lymph node metastasis (p = 0.0114) in clear cell renal cell carcinoma, advanced pT stage (p = 0.0007) in papillary renal cell carcinoma, and with advanced stage (p = 0.0023), high grade (p = 0.0005) as well as loss of ER and PR expression (each p < 0.0001) in invasive breast carcinoma of no special type (NST). In summary, pan-keratin can consistently be detected in the vast majority of epithelial tumors, although pan-keratin can be negative a fraction of renal cell, adrenocortical and neuroendocrine neoplasms. The data also link reduced pan-keratin immunostaining to unfavorable tumor phenotype in in epithelial neoplasms.

[Special mesenchymal neoplasms of the head and neck: Update from the 2022 WHO]

Similar to the approach adopted in the classification of tumors in other organs, a new feature of the current Word Health Organization (WHO) classification of the head and neck tumors is the exclusion of soft tissue tumors from single organs and their inclusion in a separate chapter devoted to them. This applies to tumors that are principally ubiquitous but show a predilection for the head and neck sites. The only exception to this rule represents those entities that are almost restricted to a specific head and neck site/organ (such as nasopharyngeal angiofibroma, sinonasal glomangiopericytoma, and biphenotypic sinonasal sarcoma), which remain in their respective organ chapters. Included among soft tissue tumors are some old but still underrecognized entities, such as phosphaturic mesenchymal tumors, and newly defined entities, such as GLI1-altered tumors. The aim of including these entities is to enhance recognition of these uncommon but likely under-recognized entities to better characterize them in the future. This review summarizes the main features of these rare entities and discusses their differential diagnoses.

Clinicopathological and Molecular Characteristics of Intraosseous Rhabdomyosarcoma Involving Head and Neck Region: A Systematic Review and Meta-Analysis

Rhabdomyosarcoma with TFCP2 rearrangement is a newly introduced spindle cell neoplasm showing predilection for craniofacial bones exhibiting highly aggressive nature and poor prognosis. Therefore, an attempt was made to delineate the entity for improved understanding and treatment outcomes through comprehensive analysis of the clinicopathological and molecular characteristics. An electronic search was carried out using MEDLINE by PubMed, Scopus, Google scholar, Cochrane library, and EMBASE databases. Original articles and case reports involving intraosseous rhabdomyosarcoma arising in head and neck region with TFCP2 fusion were included. Data were compiled and risk of bias was analyzed using JBI tool. Thirteen eligible articles were included for the quantitative analysis, which revealed 33 cases with TFCP2 fusion. Majority of the affected individuals were females (58%) with mandible being the common site. Most of the patients died within few months after diagnosis demonstrating a low mean survival rate (30 months). Odds ratio, overall survival and disease-free survival were calculated and analyzed statistically concluding that intraosseous rhabdomyosarcomas harboring TFCP2 fusion are found to be novel and dreadful neoplasms. The predilection for young age with poor prognosis exhibited by these lesions demand early diagnosis and specific treatment planning to curtail mortality.

Top 10 Histological Mimics of Neuroendocrine Carcinoma You Should Not Miss in the Head and Neck

BACKGROUND

The spectrum of neuroendocrine neoplasia (NEN) of the head and neck region is wide-ranging and diverse, including a variety of diagnoses stretching from benign and low-malignant tumor forms to highly proliferative, poor prognosis neuroendocrine carcinoma (NEC). Moreover, there are several non-neuroendocrine differential diagnoses to keep in mind as well, displaying various degree of morphological and/or immunohistochemical overlap with bona fide neuroendocrine lesions.

METHODS

Review.

RESULTS

While the growth patterns may vary, well-differentiated NEN usually display a stippled "salt and pepper" chromatin, a granular cytoplasm, and unequivocal expression of neuroendocrine markers such as chromogranin A and synaptophysin. However, these features are often less pronounced in NEC, which may cause diagnostic confusion-not the least since several non-NEC head and neck tumors may exhibit morphological similarities and focal neuroendocrine differentiation.

CONCLUSION

As patients with NEC may require specific adjuvant treatment and follow-up, knowledge regarding differential diagnoses and potential pitfalls is therefore clinically relevant. In this review, the top ten morphological and/or immunohistochemical mimics of NEC are detailed in terms of histology, immunohistochemistry, and molecular genetics.

Top 10 Significant Spindled Head and Neck Lesions to Scrutinze

BACKGROUND

Spindled lesions are a challenging area in head and neck pathology. This is particularly true in the sinonasal tract, where several uncommon entities with both unique and overlapping morphologic, immunophenotypic, and/or molecular features can occur.

METHODS

Review.

RESULTS

The clinicopathologic characteristics of biphenotypic sinonasal sarcoma and nine important differential diagnostic considerations with one or more overlapping feature are summarized to establish a practical framework for approaching spindled lesions of the sinonasal tract.

CONCLUSION

Morphologic evaluation is central to the work up of sinonasal spindle cell lesions-in particular, cellular morphology, tumor architecture and growth pattern, and the presence of admixed epithelial elements - however, focused immunohistochemical analysis of neural, myogenic, rhabdomyoblastic, epithelial, and/or melanocytic marker expression and/or ancillary tests for tumor-specific molecular alterations may be necessary for definitive diagnosis.

Molecular profile of head and neck rhabdomyosarcomas: A systematic review and meta-analysis

OBJECTIVE

This systematic review aimed to identify the molecular alterations of head and neck rhabdomyosarcomas (HNRMS) and their prognostic values.

STUDY DESIGN

An electronic search was performed using PubMed, Embase, Scopus, and Web of Science with a designed search strategy. Inclusion criteria comprised cases of primary HNRMS with an established histopathological diagnosis and molecular analysis. Forty-nine studies were included and were appraised for methodological quality using the Joanna Briggs Institute Critical Appraisal tools. Five studies were selected for meta-analysis.

RESULTS

HNRMS predominantly affects pediatric patients (44.4%), and the parameningeal region (57.7%) is the most common location. The alveolar variant (43.2%) predominates over the embryonal and spindle cell/sclerosing types, followed by the epithelioid and pleomorphic variants. PAX-FOXO1 fusion was observed in 103 cases of alveolar RMS (79.8%). MYOD1 mutation was found in 39 cases of sclerosing/spindle cell RMS (53.4%). FUS/EWSR1-TFCP2 gene fusions were identified in 21 cases of RMS with epithelioid and spindle cell morphologies (95.5%). The 5-year overall survival rate of patients was 61.3%, and MYOD1 mutation correlated with significantly higher mortality.

CONCLUSION

The genotypic profile of histologic variants of HNRMS is widely variable, and MYOD1 mutation could be a potential prognostic factor, but more studies are required to establish this.

PET-CT in Clinical Adult Oncology-VI. Primary Cutaneous Cancer, Sarcomas and Neuroendocrine Tumors

PET-CT is an advanced imaging modality with many oncologic applications, including staging, therapeutic assessment, restaging and surveillance for recurrence. The goal of this series of six review articles is to provide practical information to providers and imaging professionals regarding the best use of PET-CT for specific oncologic indications, the potential pitfalls and nuances that characterize these applications, and guidelines for image interpretation. Tumor-specific clinical information and representative PET-CT images are provided. The current, sixth article in this series addresses PET-CT in an evaluation of aggressive cutaneous malignancies, sarcomas and neuroendocrine tumors. A discussion of the role of FDG PET for all types of tumors in these categories is beyond the scope of this review. Rather, this article focuses on the most common malignancies in adult patients encountered in clinical practice. It also focuses on Food and Drug Agency (FDA)-approved and clinically available radiopharmaceuticals rather than research tracers or those requiring a local cyclotron. This information will serve as a guide to primary providers for the appropriate role of PET-CT in managing patients with cutaneous malignancies, sarcomas and neuroendocrine tumors. The nuances of PET-CT interpretation as a practical guide for imaging providers, including radiologists, nuclear medicine physicians and their trainees, are also addressed.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Soft Tissue Tumors

The fifth (5th) edition of the World Health Organization (WHO) Classification of Head and Neck Tumors introduces a new chapter dedicated to soft tissue neoplasms commonly affecting the head and neck. While the diversity, rarity, and wide anatomic range of soft tissue tumors precludes a discussion of all entities that may be found in the head and neck, the addition of this new chapter to the head and neck "blue book" aims to provide a more comprehensive and uniform reference text, including updated diagnostic criteria, of mesenchymal tumor types frequently (or exclusively) arising at head and neck sites. Since publication of the previous edition in 2017, there have been numerous advances in our understanding of the pathogenesis of many soft tissue tumors which have facilitated refinements in tumor classification, identification of novel entities, development of diagnostic markers, and improved prognostication. This review will provide a focused discussion of the soft tissue tumors included in the 5th edition WHO Head and Neck classification, with an emphasis on updates.

Adamantinoma-Like Ewing Sarcoma of the Head and Neck: A Case-Series of a Rare and Challenging Diagnosis

Adamantinoma-like Ewing sarcoma (ALES) is a rare malignant tumor characterized by EWSR1::FLI1 related fusions and complex epithelial differentiation. ALES poses a tremendous diagnostic challenge owing to its resemblance to a wide variety of common head and neck malignancies. We aimed to study the clinicopathologic spectrum of ALES diagnosed at our institute. A retrospective review of the clinical and pathologic features of all EWSR1-rearranged ALES cases was performed after confirming the diagnosis. The cases lacking EWSR1 rearrangement were excluded. A total of 7 patients were analyzed. The median age was 27 years (range 7-42 years). There were 4 males and 3 female patients. Tumors were distributed as follows: maxilla (n = 2), parotid (n = 2), nasal cavity (n = 1), ethmoid/maxilla (n = 1), and thyroid (n = 1). Tumor size ranged from 2.2 to 5.5 cm. On microscopy, tumors displayed nested-lobular architecture, monomorphic cells, and interlobular fibrotic stroma. Other features included: palisading (n = 5), squamous differentiation (n = 2), keratinization (n = 1), colonisation of salivary ducts (n = 1) and thyroid follicles (n = 1), follicle-like cysts (n = 3), calcification (n = 2), necrosis (n = 3). Mitotic rate was 4-15/2 mm². On immunohistochemistry, cytokeratins (100%), p40 (100%), strong/diffuse membranous CD99 (100%), NKX2.2 (100%), Fli-1 (71%), and synaptophysin (71%) was positive. Patients received chemotherapy (n = 7) and radiotherapy (n = 4). Two patients developed recurrence at 6 and 10 months; 3 developed metastases at 0, 6, and 25 months. ALES is a rare and aggressive malignancy that mimics diverse neoplasms common in the head and neck region. Awareness of the morphologic and immunohistochemistry spectrum of this tumor is essential to avoid diagnostic errors.

Evolving classification of rhabdomyosarcoma

Rhabdomyosarcomas comprise the single largest category of soft tissue sarcomas in children and adolescents in the United States, occurring in 4.5 million people aged below 20 years. Based on the clinicopathological features and genetic abnormalities identified, rhabdomyosarcomas are classified into embryonal, alveolar, spindle cell/sclerosing and pleomorphic subtypes. Each subtype shows distinctive morphology and has characteristic genetic abnormalities. This review discusses the evolution of the classification of rhabdomyosarcoma to the present day, together with a discussion of key histomorphological and genetic features of each subtype and the diagnostic approach to these tumours.

Introducing Fluorescence-Guided Surgery for Pediatric Ewing, Osteo-, and Rhabdomyosarcomas: A Literature Review

Sarcomas are a rare heterogeneous group of malignant neoplasms of mesenchymal origin which represent approximately 13% of all cancers in pediatric patients. The most prevalent pediatric bone sarcomas are osteosarcoma (OS) and Ewing sarcoma (ES). Rhabdomyosarcoma (RMS) is the most frequently occurring pediatric soft tissue sarcoma. The median age of OS and ES is approximately 17 years, so this disease is also commonly seen in adults while non-pleiomorphic RMS is rare in the adult population. The mainstay of all treatment regimens is multimodal treatment containing chemotherapy, surgical resection, and sometimes (neo)adjuvant radiotherapy. A clear resection margin improves both local control and overall survival and should be the goal during surgery with a curative intent. Real-time intraoperative fluorescence-guided imaging could facilitate complete resections by visualizing tumor tissue during surgery. This review evaluates whether non-targeted and targeted fluorescence-guided surgery (FGS) could be beneficial for pediatric OS, ES, and RMS patients. Necessities for clinical implementation, current literature, and the positive as well as negative aspects of non-targeted FGS using the NIR dye Indocyanine Green (ICG) were evaluated. In addition, we provide an overview of targets that could potentially be used for FGS in OS, ES, and RMS. Then, due to the time- and cost-efficient translational perspective, we elaborate on the use of antibody-based tracers as well as their disadvantages and alternatives. Finally, we conclude with recommendations for the experiments needed before FGS can be implemented for pediatric OS, ES, and RMS patients.

Lobular to Lobule: Metastatic Breast Carcinoma to Olfactory Neuroblastoma

Tumor-to-tumor metastasis (TTM) is a rare, but well-described phenomenon occurring in patients with multiple synchronous or metachronous primary malignancies. Olfactory neuroblastoma (ONB) is a rare malignant, neuroectodermal sinonasal tract tumor that occurs within the ethmoid sinus involving the cribriform plate. Very few cases of ONB have been documented to metastasize to other primary malignancies, but the reverse scenario is exceptional. During an evaluation for anosmia, a right nasal polyp was identified on imaging and endoscopy in a 66-year-old woman, with a polypectomy performed. Histologic examination showed classical features of a low-grade olfactory neuroblastoma, but within the tumor were isolated epithelioid cells which were strongly pancytokeratin immunoreactive. Review of the clinical history revealed lobular breast carcinoma treated 10 years earlier. Further evaluation with immunohistochemistry showed strong and diffuse nuclear estrogen and progesterone receptor reactivity, along with GATA3. These results confirmed TTM of an invasive lobular breast carcinoma to ONB. By employing a limited immunohistochemistry panel for all small round blue cell tumors that includes pancytokeratin, p40, S100 protein, SOX10, synaptophysin, desmin, CD99, and CD45, one is able to more accurately diagnose the classical tumor types, while also showing potentially unusual tumor features or exceptionally rare events like metastatic lobular breast carcinoma to ONB.

Head and neck rhabdomyosarcoma with TFCP2 fusions and ALK overexpression: a clinicopathological and molecular analysis of 11 cases

AIMS

Primary intraosseous rhabdomyosarcoma (RMS) is a rare entity defined by EWSR1/FUS-TFCP2 or, less commonly, MEIS1-NCOA2 fusions. The lesions often show a hybrid spindle and epithelioid phenotype, frequently coexpress myogenic markers, ALK, and cytokeratin, and show a striking propensity for the pelvic and craniofacial bones. The aim of this study was to investigate the clinicopathological and molecular features of 11 head and neck RMSs (HNRMSs) characterised by the genetic alterations described in intraosseous RMS.

METHODS AND RESULTS

The molecular abnormalities were analysed with fluorescence in-situ hybridisation and/or targeted RNA/DNA sequencing. Seven cases had FUS-TFCP2 fusions, four had EWSR1-TFCP2 fusions, and none had MEIS1-NCOA2 fusions. All except one case were intraosseous, affecting the mandible (n = 4), maxilla (n = 3), and skull (n = 3). One case occurred in the superficial soft tissue of the neck. The median age was 29 years (range, 16-74 years), with an equal sex distribution. All tumours showed mixed epithelioid and spindle morphology. Immunohistochemical coexpression of desmin, myogenin, MyoD1, ALK, and cytokeratin was seen in most cases. An intragenic ALK deletion was seen in 43% of cases. Regional and distant spread were seen in three and four patients, respectively. Two patients died of their disease.

CONCLUSIONS

We herein present the largest series of HNRMSs with TFCP2 fusions to date. The findings show a strong predilection for the skeleton in young adults, although we also report an extraosseous case. The tumours are characterised by a distinctive spindle and epithelioid phenotype and a peculiar immunoprofile, with coexpression of myogenic markers, epithelial markers, and ALK. They are associated with a poor prognosis, including regional or distant spread and disease-related death.

Clinicopathologic features and outcome of head and neck mucosal spindle cell squamous cell carcinoma

Spindle cell squamous cell carcinoma (SpC-SCC) is rare, accounting for 0.4-4% of head and neck (HN) SCCs. Better understanding of HN SpC-SCC clinicopathologic characteristics, especially features that predict outcome, is needed. We present a clinicopathologic review of 71 HN mucosal SpC-SCC from three tertiary centers. The patient population showed a median age of 63 years (range 20-91), slight male predominance (M:F = 1.6:1), and a preponderance of smokers/ex-smokers (45/71, 64%). Most lesions involved oral cavity (42/71, 59%), especially oral tongue (n = 18), and larynx (n = 20, 28%). Polypoid/exophytic growth and surface ulceration were seen in 60% and 86% of cases, respectively. Histologically, most tumors showed sarcoma-like pattern (65/70, 93%), the remaining exhibiting granulation tissue-like or fibromatosis-like patterns, and 5 lesions showed osteosarcomatous/chondrosarcomatous elements. Most tumors (53/71, 74%) showed a conventional SCC (C-SCC) component, keratinizing (86%) or non-keratinizing/basaloid (14%). Nodal metastases, seen in 22 (31%) of resection specimens, showed SpC-SCC and/or C-SCC histomorphology. By immunohistochemistry, 76% of lesions showed immunoreactivity for keratin and 62/60% of lesions were p40/p63 positive. Ki-67 proliferation index ranged from 5 to 70%. Follow-up was available on 69 patients, median of 1.1 years from the time of SpC-SCC diagnosis. The 3-, 5-, and 10-year disease-specific survival (DSS) was 62, 37, and 12%, respectively. AJCC pN stage was an independent prognostic factor for DSS and distant metastasis-free survival (DMFS), whereas the presence of C-SCC was independently associated with improved DMFS. HN SpC-SCC is rare and might be diagnostically challenging. AJCC pN stage and co-existing C-SCC component appear to be prognostically relevant.

Case Report: Paratesticular Rhabdomyosarcoma

Paratesticular rhabdomyosarcoma (RMS) accounts for only 7% of all the RMS cases. Due to the limited available data, there is no consensus on the diagnosis and management of the paratesticular tumors. Here, we interrogated two paratesticular RMS cases in 25 and 27-year-old men presenting with painless and rapidly growing mass in the scrotum. Whereas the data showed no upregulation of tumor markers such as β-human chorionic gonadotropin (β-HCG), alpha-fetoprotein (AFP), and lactate dehydrogenase (LDH), scrotal ultrasonography and magnetic resonance imaging indicated the existence of paratesticular and inguinal lesions respectively. There was local recurrence in one patient who underwent radical orchiectomy for the sarcoma one year ago. In addition, the CT scans showed no occurrence of distant metastasis. The two patients underwent radical inguinal orchiectomy or resection of the recurrent tumors with nerve-sparing retroperitoneal lymph node dissection. Histologic examination revealed embryonal RMS (eRMS) without lymph node metastasis. We highlight the importance of multi-disciplinary participation for paratesticular RMS detection and preoperative ultrasound-guided needle biopsy (UNB) for rapid confirmatory diagnosis. Complete surgical resection coupled with chemotherapy and radiotherapy is the main treatment option for the paratesticular RMS. In addition, sperm cryopreservation treatment and endocrine follow-up could increase the overall survival and quality of life of the patients.

The Most Common Mistake in Laryngeal Pathology and How to Avoid it

Upper aerodigestive tract (UADT) spindle cell squamous carcinoma (SCSC), also known as sarcomatoid carcinoma, is a high-grade subtype of conventional squamous cell carcinoma (SCC) that is histologically characterized by a combination of differentiated SCC in the form of intraepithelial dysplasia and/or invasive differentiated SCC, and the presence of an invasive (submucosal) undifferentiated malignant spindle-shaped and pleomorphic (epithelioid) cell component. Typically, SCSC presents as a superficial polypoid mass not infrequently with surface ulceration precluding identification of an intraepithelial dysplasia. Further, in many cases an invasive differentiated SCC is not identified. Adding to the complexity in such cases, is that immunohistochemical staining in a significant minority of cases is negative for epithelial-related markers but often the cells express mesenchymal-related markers. In such cases, differentiating SCSC from a reactive (benign) spindle cell proliferation or a mucosal-based sarcoma can be problematic, with treatment implications. Herein, we detail the clinical and pathologic features of laryngeal SCSC and discuss the rationale for diagnosing a carcinoma and avoiding a diagnosis of sarcoma. In our experience, such cases represent one of the more common mistakes made in laryngeal pathology. Yet, virtually all such lesions are SCSCs. The treatment and prognosis relies on the accuracy of this distinction.

Alveolar rhabdomyosarcomas involving serous cavity fluid specimens exhibit diverse cytomorphologies: A case report and review of the literature

Involvement of serous cavity specimens by alveolar rhabdomyosarcoma (ARMS) is a rare event and only a few case reports have been reported in the literature, with conflicting cytomorphologic patterns. Herein, we report on a 41-year-old man with no significant past medical history who presented with pancytopenia and shortness of breath and was found to have widely metastatic sinonasal alveolar rhabdomyosarcoma, including involvement of the pleura. The pleural fluid specimen was cellular and contained ARMS cells in small-to-medium sized three-dimensional fragments that resembled an adenocarcinoma or mesothelioma, and numerous single cells were seen in the background. The individual tumor cells demonstrated variable morphology; all were large, with varying degree of cytoplasm, and multinucleated cells were commonly seen in the background. The cells were negative for calretinin and claudin-4 and were positive for myogenin, confirming the diagnosis. Given the cytomorphologic diversity of ARMS seen in serous fluid specimens, patient history and the use of confirmatory immunostains are essential.

Sinonasal Undifferentiated Carcinoma (SNUC): From an Entity to Morphologic Pattern and Back Again-A Historical Perspective

Since the first description of sinonasal undifferentiated carcinoma (SNUC) as a distinctive highly aggressive sinonasal neoplasm with probable origin from the sinonasal mucosa (Schneiderian epithelium), SNUC has been the subject of ongoing study and controversy. In particular, the SNUC category gradually became a "wastebasket" for any undifferentiated or unclassifiable sinonasal malignancy of definite or probable epithelial origin. However, with the availability of more specific and sensitive immunohistochemical antibodies and increasing implementation of novel genetic tools, the historical SNUC category became the subject of progressive subdivision leading to recognition of specific genetically defined, reproducible subtypes. These recently recognized entities are characterized by distinctive genetic aberrations including NUTM1-rearranged carcinoma (NUT carcinoma) and carcinomas associated with inactivation of different members of the SWI/SNF chromatin-remodeling gene complex such as SMARCB1-deficient and less frequently SMARCA4-deficient carcinoma. The ring became almost closed, with recent studies highlighting frequent oncogenic IDH2 mutations in the vast majority of histologically defined SNUCs, with a frequency of 82%. A review of these cases suggests the possibility that "true SNUC" probably represents a distinctive neoplastic disease entity, morphologically, phenotypically, and genetically. This review addresses this topic from a historical perspective, with a focus on recently recognized genetically defined subsets within the SNUC spectrum.

Soft Tissue Special Issue: Skeletal Muscle Tumors: A Clinicopathological Review

Skeletal muscle tumors are classified into rhabdomyoma and embryonal, alveolar, spindle cell/sclerosing and pleomorphic rhabdomyosarcoma according to WHO classifications of tumors. These tumors arise mostly in the head and neck and, in childhood, represent the largest subset of soft tissue tumors. Although these skeletal muscle tumors show common immunoexpression of two myogenic regulatory factors, MyoD1 and myogenin, their molecular biological backgrounds are quite different. Therefore, treatment regimens vary a great deal depending on the histological subtype. Histopathologically, rhabdomyoma is characterized by well-demarcated lesions with no invasion of the surrounding tissue. Embryonal rhabdomyosarcoma is composed of primitive mesenchymal cells in various stages of myogenesis and shows heterogeneous nuclear staining for myogenin. Alveolar rhabdomyosarcoma, on the other hand, shows a proliferation of uniform primitive round cells arranged in alveolar patterns. The tumor cells at the periphery of alveolar structures adhere in a single layer to the fibrous septa. Diffuse and strong nuclear immunoexpression for myogenin is observed. In genetic backgrounds, almost all alveolar rhabdomyosarcomas contain a characteristic fusion gene such as PAX3/7-FOXO1. Spindle cell/sclerosing rhabdomyosarcoma is characterized by fascicularly arranged spindle-shaped cells or dense hyalinized collagenous matrix. NCOR2- or VGLL2-related gene fusions or MYOD1 (p.L122R) mutation is commonly recognized. Epithelioid rhabdomyosarcoma is a rare variant of rhabdomyosarcoma that shows a proliferation of epithelioid tumor cells having large vesicular nuclei, prominent nucleoli, and amphophilic to eosinophilic cytoplasm arranged in sheets. As these characteristic histological and molecular features are present in each subtype, it is possible to diagnose skeletal muscle tumors accurately.

[Neuroendocrine neoplasms of the auditory, olfactory, and visual sensory organs]

Neuroendocrine neoplasms (NENs) are infrequent in sensory organs. There are well-differentiated neuroendocrine neoplasms that should be classified as neuroendocrine tumors, in analogy to their gastrointestinal counterparts, however the nomenclature is inconsistent. The best defined entities are neuroendocrine tumors in the middle ear and ectopic pituitary adenoma in the sphenoid region. Poorly differentiated NENs most often arise in the olfactory organ and nasal cavity that are represented by olfactory neuroblastomas and poorly differentiated neuroendocrine carcinomas. They have several mimickers such as the sinonasal undifferentiated carcinoma, poorly differentiated squamous cell carcinoma, mucosal malignant melanoma, rhabdomyosarcoma, Ewing sarcoma/primitive neuroectodermal tumor and non-Hodgkin lymphoma.

[Sinonasal tumors : News from the WHO with special reference to mesenchymal entities]

The last two decades have seen significant advances in the pathology of sinonasal tract neoplasms. This was the consequence of the availability of several innovative diagnostic tools, which resulted in a dynamic evolution of entities and splitting of newly defined or conceptualized entities and subtypes that have been included in the spectrum of old heterogeneous diseases. Most of these new tumor subtypes have distinctive demographic, clinicopathologic, and biological characteristics with prognostic and therapeutic implications for individual patients. NUT carcinoma (NUT midline carcinoma) was separated from the spectrum of sinonasal undifferentiated carcinoma (SNUC) and is defined by specific recurrent translocation. On the other hand, the recently described SMARCB1-deficient carcinoma (while probably representing a distinctive clinicopathologic entity) remained as a variant in the SNUC spectrum. A new neoplasm in the spectrum of non-keratinizing carcinomas is the human papillomavirus(HPV)-related adenoid-cystic-like sinonasal carcinoma with its distinctive, albeit diverse, morphology. In the group of small round-cell malignancies, adamantinoma-like Ewing sarcoma has been delineated as an important diagnostic pitfall given its prominent epithelial differentiation. Inclusion of the biphenotypic (myoneural) sinonasal sarcoma (BSS) as a low-grade malignancy defined by recurrent PAX3/MAML3-translocation represents an important feature of the new WHO classification given the distinctive biological behavior of this low-grade non-metastasizing rare entity, which has been uniformly misclassified as a peripheral nerve sheath tumor or leiomyosarcoma in the past. Recognition of CTNNB1 mutations and STAT6/NAB2 gene fusions as defining genetic markers for sinonasal hemangio‑/glomangiopericytoma and solitary fibrous tumors, respectively, represents another important achievement in recent years. This review summarizes the new aspects in the WHO classification and also addresses recently described entities that have not been included in the WHO classification.

Diagnostic traps awaiting the head/neck pathologist: "Cytoplasm-poor" neoplasms

CONTEXT

Beyond squamous carcinoma, a variety of diagnostically challenging neoplasms arise within various head and neck sites. This is particularly the situation with neoplasms where little cellular cytoplasm is present to assist the pathologist in categorizing such lesions.

OBJECTIVE

To highlight diagnostic pitfalls that accompanying neoplasms composed primarily of 'cytoplasmically-poor' cells. These pitfalls include morphologic and immunohistochemical traps that emerge from this class of neoplasms.

DATA SOURCES

Selection of pathologic specimens from the author's personal files, and literature review.

CONCLUSIONS

Interpretative pitfalls regarding the histopathology and immunophenotype of small 'cytoplasmically-poor' neoplasms are a diagnostic hazard in head and neck surgical pathology practice, and require knowledge of histomorphologic plasticity and aberrant immunophenotyping.

The expanding morphological and genetic spectrum of MYOD1-mutant spindle cell/sclerosing rhabdomyosarcomas: a clinicopathological and molecular comparison of mutated and non-mutated cases

AIMS

Spindle cell/sclerosing rhabdomyosarcomas (SC/SRMS) feature spindled and/or rounded rhabdomyosarcomatous cells within variably hyalinised stroma. Only 30-67% of SC/SRMSs harbour neomorphic MYOD1 p.L122R mutations, indicating heterogeneity in this RMS type. We compared MYOD1-mutant and non-mutant cases to characterise the histological and genetic spectrum of mutated SC/SRMS.

METHODS AND RESULTS

Seventeen RMSs with spindled, sclerosing or hybrid histology were sequenced to identify MYOD1 and PIK3CA mutations and reappraised to assess histological features and myogenic immunophenotypes. Twelve SC/SRMSs harboured MYOD1 mutations, including homozygous p.L122R (n = 8), heterozygous p.L122R (n = 3) and heterozygous p.E118K (n = 1). MYOD1-mutant tumours affected nine females and three males aged 8-64 years (median = 22.5), had a median size of 4.2 cm (range = 2-22) and involved the head and neck (n = 7), extremities (n = 4) and mediastinum (n = 1). Fascicular/spindle histology was predominant in four cases, including one with heterologous lipoblasts in focally myxoid stroma. Four sclerosing cases mainly comprised rounded cells, including one with multinucleated tumour cells. Four cases were histologically hybrid. The only PIK3CA (p.H1047R) mutation was detected in a predominantly spindled MYOD1-p.L122R-mutated case, but not in its laser-microdissected lipoblast-containing area. All MYOD1-mutant cases exhibited diffuse MYOD1 expression but patchy myogenin reactivity. At final follow-up (median = 13.5 months), recurrences (n = 4), metastases (n = 2) or both (n = 1) occurred in seven MYOD1-mutant cases; one had died of disease. Five non-mutated cases were reclassified as spindle embryonal (n = 3), dense embryonal (n = 1) and unclassifiable (n = 1) RMSs.

CONCLUSION

MYOD1-mutant RMSs are uncommonly mutated with PIK3CA and behave aggressively with an expanded morphological and genetic spectrum, including lipoblastic differentiation, multinucleated cells and the alternative p.E118K mutation.

Update on Myogenic Sarcomas

Myogenic sarcomas include soft tissue sarcomas that show skeletal muscle differentiation (rhabdomyosarcoma) and those with smooth muscle differentiation (leiomyosarcoma). Rhabdomyosarcomas are more common in the pediatric age group and leiomyosarcomas occur more often in the adult population. Based on the clinico-pathologic features and genetic abnormalities identified, the rhabdomyosarcomas are classified into embryonal, alveolar, spindle cell/sclerosing, and pleomorphic subtypes. Each subtype shows distinctive morphology and has characteristic genetic abnormalities. In this update on myogenic sarcomas, each entity is discussed with special emphasis on recent updates in genetic findings and the diagnostic approach to these tumors.

Alveolar paratesticular rhabdomyosarcoma mimicing epididymitis: Case report and literature review

RATIONALE

Most patients with paratesticular rhabdomyosarcoma may typically present as a unilateral, painless palpable scrotum mass. However, only a few cases of RMS presenting as painful edema of the scrotum mimicing epididymitis. We herein report an unusual case of alveolar paratesticular rhabdomyosarcoma misdiagnosed as epididymitis.

PATIENT CONCERNS

A 19-year-old adolescent, presented to urologist with painful swelling of the scrotum on the left side over the preceding several days. Antibiotics were administered by physician for two months and the pain improved, but the swelling did not fade.

DIAGNOSES

Alveolar praratesticular rhabdomyosarcoma.

INTERVENTIONS

A left, soft tissue mass in the scrotum without definite metastasis or lymphadenopathy was confirmed by computed tomography (CT) and magnetic resonance imaging. A radical left orchiectomy via the inguinal approach was performed successfully.

OUTCOME

The patient received 8 cycles of adjuvant chemotherapy, the patient remains recurrence- and metastasis-free at 13 months after surgery.

LESSONS

When paratesticular RMS is presenting with symptoms of epididymitis, this malignant tumor is usually overlooked. When patients complain of painful scrotal swelling, RMS arise from paratesticular tissue should be considered.