Myoepithelioma-like Tumor of the Vulvar Region Presenting as a Nonmyxoid Spindle-Cell Neoplasm: A Potential Histologic Mimicker of Solitary Fibrous Tumor

Pathologic and genomic characteristics of myoepithelioma-like tumor of the vulvar region: three case reports

BACKGROUND

Myoepithelioma-like tumor of the vulvar region (MELTVR) is a rare type of soft tissue mesenchymal tumor. While MELTVR exhibits histological characteristics similar to soft tissue myoepithelial tumors, its immunohistochemical and genetic features differ significantly. To date, no comprehensive genomic analysis of this tumor has been conducted.

CASE PRESENTATION

We present the clinicopathological features, imaging characteristics, and immunophenotypes of three patients with MELTVR, along with their genomic characterization through high-throughput sequencing. Immunohistochemical analysis revealed that these tumors were negative for SMARCB1, S-100, CD34, CD31, SMA, Desmin, and Keratin. The Ki-67 proliferation index for tumor cells ranged from 10 to 35%. Genomic analyses showed copy number deletions in the SMARCB1 gene in all three patients. The tumor mutational burden was relatively low, ranging from 1.35 to 4.33. Additionally, two tumors exhibited fusion mutations involving PPP6R3::FHDC1 and MYH9::MYH6, while no fusions involving EWSR1, NR4A3, or FUS were detected.

CONCLUSIONS

This study reports the first comprehensive genomic analysis of three patients with MELTVR, potentially identifying therapeutic targets for this rare tumor.

Myoepithelioma-Like Tumor of the Vulvar Region: A Clinicopathologic Study of Four Cases

Myoepithelioma-like tumors of the vulvar region (MELTVR) are solid tumors found in the vulva of adult women. They have a similar histopathology to myoepithelioma but differ in immunohistochemical phenotype and genetic changes. In this study, we report four examples of MELTVR, occurred in the external genitalia and mons pubis of adult women aged 32 to 39 years. The tumors presented as subcutaneous masses without obvious tenderness. The tumors were composed of a mixture of myxoid and nonmyxoid components, and myxoid areas accounted for 5% to 80% of the tumor volume. The tumor cells were spindle-shaped or epithelioid, with abundant cytoplasm, vesicular nuclei, and small nucleoli. The nuclear atypia was mild to moderate, with 0 to 10 mitotic figures per 10 high-power fields. Immunohistochemically, all four tumors showed consistent positivity for EMA, calponin and ER; three tumors exhibited PR expression. All tumors were negative for S100 protein and SMA. AE1/AE3 expression was absent in all except one tumor, which showed rare positivity. SMARCB1/INI1 expression was deficient in all tumors. EWSR1 and FUS rearrangements were absent. All tumors were treated through surgery. All patients were alive without recurrence on most recent follow-up. Together, this overview of four additional tumors of MELTVR offers further insight into this rare and poorly understood disease.

Myoepithelioma-Like Tumor of the Vulva

Background: Myoepithelioma-like tumor of the vulvar region (MELTVR) is a rare mesenchymal tumor that typically arises in the female vulva. Case Presentation: Here, we report a case of a 48-year-old woman who presented with a 2-year history of subcutaneous mass in the vulvar region. As the mass rapidly increased in the last 2 months, personal slight swelling pain appeared. Histologically, the tumor exhibited a distinctive feature of abundant tumor cells and sparse mucus regions. While each region appeared alternately, the sparse mucus region was about 30% of the whole tumor. The tumor had two types of cells, namely, epithelioid and spindle cells. The tumor-rich region demonstrated a cell type of epithelioid, showing hermaphroditic cytoplasm, the center-located nucleus, and abundant chromatin of fasciculate or cord-braid arrangement, whereas the cell of the mucus region was fusiform or epithelioid with partial vacuole-shaped and small visible nucleolus, exhibiting red-stained cytoplasm and loose chromatin. Immunohistochemically, vimentin, smooth muscle actin (SMA), and P16 were diffuse positive in tumor cells, whereas desmin, cytokeratin (CK), P40, P63, CK5, HMB45, MyoD1, myogenin, S100, and SOX10 were all negative. While the proliferation index of Ki-67 was about 7%, the expression of SMARCBl/lNI-1 protein was absent. The pathological diagnosis is myoepithelioma-like tumor of the vulva (right labia majora). Finally, the tumor was surgically and completely removed, and no recurrence or metastasis was found after 6 months of follow-up. Conclusions: Histologically, the morphology of MELTVR is changeable and variation existed for each individual tumor. Moreover, it needs to be differentiated from various other types of tumors, whereas more reports and studies are required to further clarify MELTVR.

Myoepithelioma-like tumors of the vulvar region: A case report and review of the literature

Myoepithelioma-like tumors of the vulvar region (MELTVR) is a kind of solid tumor newly recognized in recent years, which is characterized by mesenchymal tumors of adult female vulva. The histopathology is similar to myoepithelioma, but the immunohistochemical phenotype and genetic changes are different from myoepithelioma. It usually has clear boundary and partial capsule, mixed with two forms of cells (epithelioid and spindle), the cells are mild, the nucleoli are clear, mitoses are rare, some cases have myxoid differentiation. In this article, a case of MELTVR diagnosed in our hospital is discussed. The patient was a 43-year-old female who finds a neoplasm in the pubic tubercle 4 months ago. Local resection was performed. Pathological examination showed that the boundary of the tumor was clear with partial capsule. The cells were arranged in cords or nests, and partially infiltrated the surrounding adipocytes. The tumor cells had two morphologies, epithelioid or spindle shaped. The spindle type cells were dominant, with bright cytoplasm, obvious nucleoli, rare nuclear mitosis (about 1/10HPF), and no necrosis was observed. Immunohistochemically, the tumor cells were positive for vimentin, epithelial membrane antigen, estrogen receptor, progestogen receptor, calponin and were partially positive for cathepsin k. INI1/SMARCB1 expression was deficient. There was no recurrence or metastasis during the 8-month-long follow-up. The unique feature of this case was that the site of the disease was not the vulva, but in front of the pubic tubercle, there was no large amount of mucus production, and the cytoplasm of most tumor cells was transparent. Due to our limited knowledge of MELTVR, its pathogenesis and tissue origin are not clear. Clinicians should be aware of such potential patients.

Myoepithelioma-like tumour of the vulval region: A case report

Myoepithelioma-like tumours of the vulvar region (MELTVR) are a newly described group of spindle cell neoplasm. Morphologically, they consist of epithelioid to spindled cells in a myxoid to collagenous stroma and can resemble epithelioid sarcomas, myoepithelial carcinomas or extraskeletal myxoid chondrosarcomas. However, they have a distinct pattern of immunohistochemical staining characterised by positivity for EMA, ER, PR and negativity for cytokeratin, GFAP and S100. Nuclear staining for INI-1 is lost. In addition, they lack the characteristic gene arrangements of these other lesions. MELTVR can recur locally when incompletely excised, however, do not appear to metastasize. We report a case of a MELTVR in a 49-year-old woman arising in the right mons pubis.

Myoepithelioma of soft tissue and bone, and myoepithelioma-like tumors of the vulvar region: Clinicopathological study of 15 cases by PLAG1 immunohistochemistry

We demonstrated the clinicopathological findings of 13 myoepitheliomas of soft tissue and bone (MESTBs) and two myoepithelioma-like tumors of the vulvar region (MELTVRs), focusing on the association between nuclear atypia and clinical course, and the utility of immunohistochemistry (IHC) of pleomorphic adenoma gene 1 (PLAG1) for the pathological diagnosis of these tumors. Of the 13 MESTBs, eight, one and four cases exhibited mild, moderate and severe nuclear atypia, respectively. Two cases with venous invasion showed severe nuclear atypia and both died of advanced disease. Two MELTVR cases showed moderate nuclear atypia and had no evidence of disease after surgery. On IHC, 12 of 13 (92.3%) MESTBs showed PLAG1 immunoreactivity and none of the MELTVRs expressed PLAG1. In addition, MELTVRs showed loss of INI1 expression. In contrast, all MESTBs retained INI1 expression. Fluorescence in situ hybridization detected EWSR1, FUS and PLAG1 rearrangement in 5 (38.5%), 0 (0%) and 2 (15.4%) of the 13 MESTBs, respectively. No EWSR1, FUS and PLAG1 rearrangement were observed in the METLVRs. In conclusion, MESTBs with both severe nuclear atypia and venous invasion would be indicative of malignant potential. PLAG1 might be a useful IHC marker in MESTB diagnosis.

Myoepithelioma-like tumor of the vulvar region: a case report in China and review of the literature

Background

Myoepithelioma-like tumor of the vulvar region (MELTVR) is a recently described mesenchymal neoplasm which typically arising in vulvar regions of adult women.

Case presentation

Here we report a case of a 65-year-old woman who presented with a 6-year history of subcutaneous mass in the vulvar region. The mass had recently increased in size continuously. Histologically, the tumor cells had an epithelioid to spindled shape. Epithelioid tumor cells proliferated singly or in a loosely cohesive manner with myxoid areas, while spindled tumor cells grew in diffuse sheets or storiform arrangements mainly in nonmyxoid areas. Immunohistochemically, the tumor cells were positive for vimentin, epithelial membrane antigen, calponin, and were partially mild to moderate positive for estrogen receptor, but completely negative for S100 protein, glial fibrillary acidic protein, CD34, desmin, SMA and cytokeratin. INI1/SMARCB1 expression was deficient. EWSR1 and FUS genes were intact tested by fluorescence in situ hybridization analysis. Based on these findings, we diagnose this case as MELTVR. The patient remained relapse-free after the lesion was widely excised during 8 months follow-up.

Conclusions

This disease should be included in the differential diagnostic list of vulvar tumors with epithelioid to spindled morphology. Recognition of its histopathological features and immunohistochemical reactivity will help to understand the tumor better.

Myoepithelioma-like tumor of the vulvar region showing infiltrative growth and harboring only a few estrogen receptor-positive cells: A case report

Recently, a new entity "myoepithelioma-like tumor of the vulvar region (MELTVR)" was proposed as a rare mesenchymal neoplasm arising in vulvar regions of adult women. While MELTVRs morphologically resemble soft tissue myoepitheliomas and extraskeletal myxoid chondrosarcomas, they have a unique immunohistochemical profile (positive for epithelial membrane antigen and estrogen receptor, negative for S100 protein and glial fibrillary acidic protein, and loss of INI1/SMARCB1 expression), and lack EWSR1 and NR4A3 gene rearrangement, as seen by fluorescence in situ hybridization. MELTVRs are usually well-demarcated tumors, with no reports of extensive infiltrative growth. In the current report, we present an unusual case of MELTVR showing infiltrative growth and harboring only a few estrogen receptor-positive cells, which might indicate a variation in this rare tumor.