GLI activated epithelioid cell tumour: report of a case and proposed new terminology

GLI1-Altered Soft Tissue Tumor in the Tongue-A Case Report and Literature Review

Background: Soft tissue tumors with fusions or amplifications of the GLI1 gene have distinctive molecular characteristics and have recently been considered a unique pathological entity, thus named "GLI1-altered soft tissue tumors." It is a rare mesenchymal neoplasm that involves soft tissues at any site. Case presentation: We report an example of this condition in a 13-year-old Chinese male patient who presented with a mass in the tongue. The tumor was multilobulated; the tumor cells were arranged in nests and sheets, had a rich, delicate fibrovascular network, and were separated by a hyalinized fibrous stroma. The tumor cells were epithelioid to ovoid, with variable eosinophilic to pale vacuolated cytoplasm and round to oval nuclei. Immunostaining revealed that the tumor cells were positive for CDK4 and CD56. Fluorescence in situ hybridization (FISH) for GLI1 translocation was positive, with a high level of amplification of the translocated segment. Literature review: We present a comprehensive literature review of this condition, focusing on its clinical presentation, histological features, immunohistochemical profile, molecular characteristics, and prognosis.

GLI1-Altered Mesenchymal Tumors

GLI1-altered mesenchymal tumors comprise an emerging group of neoplasms characterized by fusions or amplifications involving GLI1, a gene that encodes a key regulator of the Hedgehog signaling pathway. In recent years, tumors with GLI1 alterations have been reported across a variety of anatomic sites and a broad age range. Although these tumors can exhibit a wide morphologic spectrum and a variable immunophenotype, they frequently present with monomorphic ovoid cells arranged in distinctive nests with a rich, arborizing vascular network. Recent evidence indicates that they have the potential to metastasize, which suggests that they may be best considered a sarcoma.

GLI1-Altered Mesenchymal Tumors With ACTB or PTCH1 Fusion: A Molecular and Clinicopathologic Analysis

Mesenchymal tumors with GLI1 fusions or amplifications have recently emerged as a distinctive group of neoplasms. The terms GLI1-altered mesenchymal tumor or GLI1-altered soft tissue tumor serve as a nosological category, although the exact boundaries/criteria require further elucidation. We examined 16 tumors affecting predominantly adults (median age: 40 years), without sex predilection. Several patients had tumors of longstanding duration (>10 years). The most common primary site was soft tissue (n = 9); other sites included epidural tissue (n = 1), vertebra (n = 1), tongue (n = 1), hard palate (n = 1), and liver (n = 1). Histologically, the tumors demonstrated multinodular growth of cytologically uniform, ovoid-to-epithelioid, occasionally short spindled cells with delicate intratumoral vasculature and frequent myxoid stroma. Mitotic activity ranged from 0 to 8 mitoses/2 mm2 (mean 2). Lymphovascular invasion/protrusion of tumor cells into endothelial-lined vascular spaces was present or suspected in 6 cases. Necrosis, significant nuclear pleomorphism, or well-developed, fascicular spindle-cell growth were absent. Half demonstrated features of the newly proposed subset, "distinctive nested glomoid neoplasm." Tumors were consistently positive for CD56 (n = 5/5). A subset was stained with S100 protein (n = 7/13), SMA (n = 6/13), keratin (n = 2/9), EMA (n = 3/7), and CD99 (n = 2/6). Tumors harbored ACTB::GLI1 (n = 15) or PTCH1::GLI1 (n = 1) fusions. The assays used did not capture cases defined by GLI1 amplification. We also identified recurrent cytogenetic gains (1q, 5, 7, 8, 12, 12q13.2-ter, 21, and X). For patients with available clinical follow-up (n = 8), half were disease free. Half demonstrated distant metastases (lungs, bone, or soft tissue). Of cases without follow-up (n = 8), 2 were known recurrences, and 1 was presumed metastasis. Our results imply a more aggressive biological potential than currently reported. Given the possibility for metastasis and disease progression, even in cytologically bland, nested tumors, close clinical surveillance, akin to that for sarcoma management, may be indicated. The term GLI1-altered mesenchymal tumor with malignant potential is proposed.

GLI1-altered Mesenchymal Tumor Involving the Duodenum: Case Report and Literature Review

GLI1-altered mesenchymal tumor is an emerging entity with distinctive clinicopathologic features. It shows a distinctive monomorphic round to epithelioid morphology, nested to trabecular pattern of growth, and S100+/SOX10-/SMA-immunophenotype. We report an example of this entity arising in the duodenum. A 31-year-old man presented with anemia for 1 year, a mass in the duodenal bulb was found for 9 days. Histopathologic examination revealed the tumor with distinct multilobulated architecture, a monomorphic appearance of round to epithelioid cells arranged in papillary structures, nests, cords, solid, reticular patterns, and hyalinized stroma surrounding a rich capillary network. The neoplastic cells had amphophilic to light eosinophilic or clear cytoplasm, uniform round nuclei with fine chromatin and inconspicuous nucleoli. Immunohistochemical analysis revealed strong positivity for vimentin, S100, CD56, CyclinD1, and negativity for SOX10, SMA, melan-A, HMB-45, synaptophysin, and a variety of other markers. Based on the morphology and immunophenotype, molecular studies were performed, which revealed the presence of an ACTB::GLI1 fusion transcript, confirming the diagnosis of GLI1-altered mesenchymal tumor.

Primary Cutaneous Epithelioid Mesenchymal Tumor With a Novel ATP2B4::GLI1 Gene Fusion

ABSTRACT

GLI1 gene alterations (rearrangement or amplification) have been found in several bone and soft tissue tumors including pericytic tumors, gastric plexiform fibromyxoma, gastroblastoma, and a various group of epithelioid tumors with regional recurrence or distant metastasis. In this article, we describe a case of primary cutaneous epithelioid mesenchymal tumor harboring hitherto not reported ATP2B4::GLI1 gene fusion. A 42-year-old man presented with a growing firm lesion on the left postauricular scalp. Microscopically, the shave biopsy specimen revealed a dermal-based nodular proliferation of relatively monotonous epithelioid cells with round to ovoid nuclei and pale eosinophilic cytoplasm, accompanied by prominent stromal vasculature. Significant cytologic atypia, necrosis, and mitotic activity were absent. The tumor cells were partially positive for CD34 and S-100 protein, but were negative for other markers, including SOX-10, keratins, and myogenic markers. An ATP2B4::GLI1 gene fusion was identified by next-generation sequencing. Array CGH was also performed, but it did not show relevant chromosomal copy number changes. Awareness of this rare cutaneous tumor, and thus, reporting of additional cases is necessary for further delineating its full clinicopathologic spectrum.

GLI1-altered epithelioid soft tissue tumor: A newly described entity with a predilection for the tongue

A novel subset of epithelioid soft tissue tumors with GLI1 gene fusions or amplifications has recently been characterized. Histologically, these tumors typically exhibit multinodular or plexiform growth of ovoid, round to epithelioid neoplastic cells, with a distinctive nested architecture separated by a rich delicate arborizing vascular network. The immunoprofile is variable and nonspecific, indicating no definitive line of differentiation. GLI1-altered epithelioid soft tissue tumor is considered to be a low-grade sarcoma; however, with a limited number of cases reported, the biologic behavior of this entity is unclear. Interestingly, these tumors frequently occur in the head and neck, with a clear predilection for the tongue. To date, 11 cases of lingual GLI1-altered epithelioid soft tissue tumors have been reported in the English literature, and none showed evidence of recurrence or metastasis. Herein, we report an additional case of lingual GLI1-altered epithelioid soft tissue tumor harboring GLI1 fusion in a 56-year-old man with regional nodal metastasis and distant metastasis to increase the awareness of this entity among oral pathologists and clinicians. An accumulation of similar cases is mandatory to clarify biological behaviors and also for the development of new therapeutic strategies.

GLI1-altered mesenchymal tumor: a clinicopathological and molecular analysis of ten additional cases of an emerging entity

We report 10 additional cases of GLI1-altered mesenchymal tumor to further delineate its clinicopathological and molecular spectrum. There were seven males and three females with a median age of 31 years (range 1.3 ~ 75 years). Five tumors arose in the oral cavity, one each in the stomach, uterine cervix, elbow, groin, and thigh. Histologically, all cases except one were composed of monomorphic round to epithelioid cells showing an infiltrative multinodular growth pattern. The neoplastic cells were surrounded by a rich network of capillary vessels. Vessel invasion or subendothelial protrusion into the vascular space was commonly present. One tumor developed regional lymph node metastasis. The remaining case showed a predominantly spindle cell tumor. By immunohistochemistry, most tumors showed diffuse staining of CD56 (8/8) with variable expression of S100 protein (7/8). In three tumors harboring amplified genes, strong and diffuse nuclear staining of MDM2 (2/3) and CDK4 (3/3) were noted. Next-generation sequencing (NGS) studies revealed GLI1 fusions in 7 cases and GLI1 amplification in 2 cases, which were validated by fluorescence in situ hybridization (FISH) analysis in the majority of cases. One case did not show fusion gene by RNA-seq, but FISH revealed both amplification and break-apart of GLI1 gene. Follow-up information showed local recurrences in two patients. All other patients remained disease-free at the last follow-up. Our study further demonstrates that mesenchymal tumors with GLI1 alterations represent a distinctive clinicopathological entity. Although the tumor has a propensity for the tongue, it can also arise in somatic soft tissues as well as in visceral organs. Based on the characteristic morphological features and genomic profiles, we propose the term "GLI1-altered mesenchymal tumor" to describe this emerging entity.

Primary cutaneous epithelioid mesenchymal neoplasm with ACTB-GLI1 fusion: a case report

Mesenchymal tumors harboring GLI1 gene abnormalities are a rare but distinctive group of neoplasms whose clinicopathologic features are currently evolving. In particular, examples of this tumor with ACTB-GLI1 gene fusion, tentatively termed ACTB-GLI1 epithelioid mesenchymal neoplasm (EMN), show a distinctive monomorphic round-to-epithelioid morphology, nested to trabecular pattern of growth, and S100+/SOX10-/SMA- immunophenotype. We report the first case of this entity arising exclusively in the skin. A 69-year-old man with no prior history of neoplasia presented with a 1.5-cm raised lesion on the left buttock. Histopathologic examination revealed a diffuse dermal proliferation of small, monomorphic, round-to-ovoid cells with hyperchromatic nuclei, focally enlarged nucleoli, and minimal eosinophilic to clear-staining cytoplasm. These cells were arranged in confluent nests and trabeculae in a background of fibrocollagenous to focally myxoid stroma. Immunohistochemical analysis revealed strong positivity for S100 and CD56, and negativity for SOX-10, SMA, Melan-A, HMB-45, and a variety of other markers. Based on the morphology and immunophenotype, molecular studies were performed, which revealed the presence of an ACTB-GLI1 fusion transcript, confirming the diagnosis. Given the morphologic overlap of this tumor with other cutaneous round cell neoplasms and its potential for malignant behavior, ACTB-GLI1 EMN is an important entity for pathologists to recognize.

Plexiform fibromyxoma: Review of rare mesenchymal gastric neoplasm and its differential diagnosis

Plexiform fibromyxoma (PF) is a very rare mesenchymal neoplasm of the stomach that was first described in 2007 and was officially recognized as a subtype of gastric mesenchymal neoplasm by World Health Organization (WHO) in 2010. Histologically, PF is characterized by a plexiform growth of bland spindle to ovoid cells embedded in a myxoid stroma that is rich in small vessels. The lesion is usually paucicellular. While mucosal and vascular invasion have been documented, no metastasis or malignant transformation has been reported. Its pathogenesis is largely unknown and defining molecular alterations are not currently available. There are other mesenchymal tumors arising in the gastrointestinal tract that need to be differentiated from PF given their differing biologic behaviors and malignant potential. Histologic mimics with spindle cells include gastrointestinal stromal tumor, smooth muscle tumor, and nerve sheath tumor. Histologic mimics with myxoid stroma include myxoma and aggressive angiomyxoma. Molecular alterations that have been described in a subset of PF may be seen in gastroblastoma and malignant epithelioid tumor with glioma-associated oncogene homologue 1 (GLI1) rearrangement. The recent increase in publications on PF reflects growing recognition of this entity with expansion of clinical and pathologic findings in these cases. Herein we provide a review of PF in comparison to other mesenchymal tumors with histologic and molecular resemblance to raise the awareness of this enigmatic neoplasm. Also, we highlight the challenges pathologists face when the sample is small, or such rare entity is encountered intraoperatively.