Ectomesenchymal chondromyxoid tumor: a comprehensive updated review of the literature and case report

Ectomesenchymal chondromyxoid tumor of the oral cavity: a report of 5 new cases with comprehensive review of the literature and clinicohistopathologic features

OBJECTIVE

An ectomesenchymal chondromyxoid tumor (ECT) is an uncommon soft tissue tumor with an enigmatic histogenesis and striking predilection for the tongue. We present 5 new cases and review the literature.

STUDY DESIGN

We performed a retrospective search for ECTs within the University of Kentucky Oral Pathology Biopsy Service and the published literature.

RESULTS

Five new cases from the biopsy archives and 103 well-documented ECT cases from the literature were compiled and reviewed. Whereas 89.8% of ECT are found on the anterior/dorsal/lateral/unspecified tongue, 4.6% are on the posterior/base of tongue. Six extralingual cases are reported. The age ranges from 2.3 to 78 years with an average of 40. Most ECT react with GFAP (92.8%) and S-100 protein (91.3%). Whereas 21/23 cases demonstrated a RREB1-MKL2 fusion, EWSR1 gene mutations are identified in 4 cases.

CONCLUSIONS

Most ECT are readily diagnosed on routine histopathology in combination with tumor site, immunohistochemical findings, and molecular findings; however, a subset share overlapping features with myoepithelioma of soft parts. As further molecular analysis is performed on this tumor, we may find that a subset of previously diagnosed ECT relate to or represent myoepithelioma or conversely fall under the spectrum of the pluripotent ECT.

RREB1::MRTFB fusion-positive extra-glossal mesenchymal neoplasms: A series of five cases expanding their anatomic distribution and highlighting significant morphological and phenotypic diversity

The RREB1::MRTFB (former RREB1::MKL2) fusion characterizes ectomesenchymal chondromyxoid tumors (EMCMT) of the tongue. Only five molecularly confirmed extra-glossal EMCMT cases have been reported recently; all occurring at head and neck or mediastinal sites. We herein describe five new cases including the first two extracranial/extrathoracic cases. The tumors occurred in three male and two female patients with an age ranging from 18 to 61 years (median, 28). Three tumors were located in the head and neck (jaw, parapharyngeal space, and nasopharyngeal wall) and two in the soft tissue (inguinal and presacral). The tumor size ranged from 3.3 to 20 cm (median, 7). Treatment was surgical without adjuvant treatment in all cases. Two cases were disease-free at 5 and 17 months; other cases were lost to follow-up. Histologically, the soft tissue cases shared a predominant fibromyxoid appearance, but with variable cytoarchitectural pattern (cellular perineurioma-like whorls and storiform pattern in one case and large polygonal granular cells embedded within a chondromyxoid stroma in the other). Two tumors (inguinal and parapharyngeal) showed spindled to ovoid and round cells with a moderately to highly cellular nondescript pattern. One sinonasal tumor closely mimicked nasal chondromesenchymal hamartoma (NCMH). Mitotic activity was low (0-5 mitoses/10 hpfs). Immunohistochemical findings were heterogeneous with variable expression of S100 (2/5), EMA (2/3), CD34 (1/4), desmin (1/4), and GFAP (1/3). Targeted RNA sequencing revealed the same RREB1::MRTFB fusion in all cases, with exon 8 of RREB1 being fused to exon 11 of MRTFB. This study expands the topographic spectrum of RREB1::MRTFB fusion-positive mesenchymal neoplasms, highlighting a significant morphological and phenotypic diversity. Overall, RREB1::MRTFB-rearranged neoplasms seem to fall into two subcategories: tumors with lobulated, chondroid, or myxochondroid epithelioid morphology (Cases 2 and 3) and those with more undifferentiated hypercellular spindle cell phenotype (Cases 1, 4, and 5). Involvement of extracranial/extrathoracic sites and the NCMH-like pattern are novel. The biology of these likely indolent or benign tumors remains to be verified in the future.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Tumours of the Oral Cavity and Mobile Tongue

The fifth chapter of the upcoming fifth edition of the 2022 World Health Organization Classification of Tumours of the Head and Neck titled Tumours of the oral cavity and mobile tongue, has had some modifications from the 2017 fourth edition. A new section "Non-neoplastic Lesions", introduces two new entries: necrotizing sialometaplasia and melanoacanthoma. The combined Oral potentially malignant disorders and Oral epithelial dysplasia section in the 2015 WHO has now been separated and submucous fibrosis and HPV-associated dysplasia are also discussed in separate sections. Carcinoma cuniculatum and verrucous carcinoma are described in dedicated sections, reflecting that the oral cavity is the most common location in the head and neck for both these entities which have distinct clinical and histologic features from conventional squamous cell carcinoma. This review summarizes the changes in Chapter 5 with special reference to new additions, deletions, and sections that reflect current clinical, histological, and molecular advances.

The Role of Immunohistochemistry for Primary Oral Diagnosis in a Brazilian Oral Pathology Service

A proper antibody panel selection is one of the most important factors to reach an adequate diagnosis in challenging cases. This retrospective study was designed to determine the contribution of immunohistochemistry (IHC) in the primary diagnosis of oral diseases in one of the main services of oral pathology in the State of São Paulo, Brazil, and to identify the most common antibodies used, and recommend diagnostic algorithms based on our experience with challenging lesions. A total of 1698 IHC stains were performed in 401 cases from a total of 28,804 cases received from public dental clinics and private dental practitioners within a period of 13 years, representing a frequency of 1.4% of IHC solicitations. Among these, 112 (28%) were mandatory to reach a final diagnosis and 255 (63.6%) were confirmative. In 34 (8.4%) cases, it was not possible to reach a conclusive/final diagnosis, even with IHC. Regarding the nature of the lesions, 210 (52.3%) were benign, 163 (40.6%) were malignant tumors, 13 (3.2%) were reactive, 10 (2.5%) were premalignant, and 5 (1.2%) were lesions of uncertain malignancy. Small amount of tissue of some incisional biopsies, overlapping features of spindle cell lesions (epithelial, neural, melanocytic, smooth muscle, endothelial, and fibroblastic/myofibroblastic cell differentiation), and overlapping features of salivary gland lesions were the most frequent challenges in which IHC stains were requested. Spindle cell lesions were the most frequent (22%) among all cases that required IHC to reach a final diagnosis. The implementation of IHC for routine practice requires a wide range of markers, proper antibody selection, and knowledge to interpret the subjectivity of staining. The inherent limitation of incisional biopsies was pointed as a reason to inconclusive diagnosis, despite a wide range of antibodies that our laboratory displays.

Ectomesenchymal Chondromyxoid Tumor: A Rare Association With an Asymmetrical Soft Palate Cleft

Ectomesenchymal chondromyxoid tumor (ECT) is a rare oral lesion first described by Smith et al. in 1995. These tumors are typically painless, slow growing and benign masses occurring predominantly on the anterior tongue dorsum. Prior to this seminal report, many ECTs may have been misdiagnosed due to the histological similarities with other lesions. Immunohistochemical stains aid in definitive diagnosis of an ECT. A total of 39 papers since published have reported 96 patients with ECT. Most lesions involve the anterior aspect of the tongue, with only 6 occurring in the posterior tongue and 2 involving the hard palate. ECTs are considered to develop from ectomesenchymal cells of neural crest cells that have migrated to the tongue during embryological development. This paper is of a rare case of ECT of the posterolateral tongue occurring in association with an unusual asymmetrical soft palate cleft. It is postulated that since the tongue develops before the formation of the soft palate, an ECT lesion occurring on the posterior aspect may have a causal contribution to the development of the soft palate cleft.

Ossifying fibromyxoid tumor of the oral cavity: rare case report and long-term follow-up

Ossifying fibromyxoid tumor (OFMT) is a rare mesenchymal soft tissue benign neoplasm with an uncertain line of differentiation, which arises most frequently in extremities. The head and neck region involvement is uncommon, with only ten intraoral cases published in the English-language literature. One additional case of OFMT is reported here, including a literature review of intraoral reported cases. A 45-year-old female patient presented a painless nodule involving the buccal mucosa of approximately two years duration, measuring nearly 1.3 cm in maximum diameter. The main histopathological features include ovoid to round cells embedded in a fibromyxoid matrix with a perpheral shell of lamellar bone. Immunohistochemically, the tumor showed immunoreactivity for vimentin and S100. No recurrence has been detected after 7 years of follow-up.

Mesenchymal tumours with RREB1-MRTFB fusion involving the mediastinum: extra-glossal ectomesenchymal chondromyxoid tumours?

AIMS

Ectomesenchymal chondromyxoid tumour (ECT) is a rare benign intraoral tumour which almost exclusively presents as a small mass of the anterior dorsal tongue. Recently, the RREB1-MRTFB (previously known as MKL2) fusion gene has been identified in 90% of ECTs, all located in the tongue, emphasising its genetic distinctiveness. Here, we report two mesenchymal tumours involving the superior mediastinum of adult women with RREB1-MRTFB fusions.

METHODS AND RESULTS

Both tumours presented as well-circumscribed paravertebral masses that were clinically suspected to be schwannoma. After fragmented resection, recurrence was not observed at 27 and 18 months. Although tumours were originally unclassifiable, next-generation sequencing detected identical RREB1 (exon 8)-MRTFB (exon 11) fusion transcripts, which were validated by reverse transcriptase-polymerase chain reaction, Sanger sequencing, and fluorescence in-situ hybridisation. Both tumours shared hyalinised areas with round cells embedded in a cord or reticular manner. The tumour cells showed mild nuclear atypia of possible degenerative type with very low mitotic activity, and were at least focally positive for S100, glial fibrillary acidic protein, smooth muscle actin and epithelial membrane antigen. Overall, these findings suggest that they may represent previously undescribed extra-glossal ECT involving the mediastinum. However, the histology was not classic for ECT, because that in case 2 was predominated by storiform growth of spindle cells, whereas the tumour in case 1 lacked myxoid change.

CONCLUSIONS

We have provided the first evidence that RREB1-MRTFB fusion is not limited to tumours in the head region, and whether such tumours represent extra-glossal ECTs requires further research.

Expanding Awareness of the Distribution and Biologic Potential of Ectomesenchymal Chondromyxoid Tumor

Ectomesenchymal chondromyxoid tumor is a rare neoplasm of uncertain histogenesis that typically occurs in the anterior dorsal tongue. Recent reports in the literature have described rare examples of gingival, palatal and tonsillar lesions. Histologically, ectomesenchymal chondromyxoid tumors are typically well-circumscribed, lacking overtly aggressive features. Herein we report a tumor arising in the right mandible that is morphologically and molecularly consistent with ectomesenchymal chondromyxoid tumor. This case furthers awareness of the extra-glossal distribution of this neoplasm; moreover, it suggests that a subset of these tumors have the potential for locally aggressive behaviour.

An ectomesenchymal chondromyxoid tumour on the lateral border of the tongue

Ectomesenchymal chondromyxoid tumour (ECT) is an extremely rare intraoral mesenchymal tumour. Most of these tumours have been identified on the anterior aspect of the dorsal surface of the tongue. ECT is difficult to diagnose because of its rarity. We report a case of ECT arising on the lateral border of the tongue in a 67-year-old woman. The tumour, measuring 20 × 10 mm in size, was surgically removed. Histopathologically, the tumour was composed of small polygonal cells arranged in sheets, with a myxoid or hyalinized stroma. The tumour boundary was clear; however, the tumour showed a multinodular structure expanding along the tongue surface without obvious capsule. Careful examination revealed the tumour nodule to be spreading in a skip lesion-like fashion away from the main part of the tumour in the striated muscle layer. Although there was no evidence of recurrence at 18 months after the surgery, our observations suggest that surgery for ECT resection with a safety margin is more appropriate than enucleation.

Ectomesenchymal chondromyxoid tumour: an uncommon characteristic tumour of the anterior tongue

Ectomesenchymal chondromyxoid tumour (ECMT) is a rare benign tumour which classically presents in the anterior tongue. This tumour is grossly under-reported due to lack of immunohistochemical staining in many centres. We report a 46-year-old man who presented with mass in the anterior tongue and was diagnosed with ECMT. Further management of this lesion is explained with a review of the literature.