Primitive myxoid mesenchymal tumor of infancy: a report of a further case with locally aggressive behavior

Primitive Myxoid Mesenchymal Tumor of Infancy: A Lost Battle

Primitive myxoid mesenchymal tumor of infancy (PMMTI) is a low to intermediate-grade, poorly differentiated myofibroblastic tumor and is characterized by its tendency to recur locally. It commonly occurs in the 1st year of life and is predominantly seen in the axial skeleton and rarely in the retroperitoneum. We report one such case of PMMTI, which is the second case reported in English literature.

Treatment of primitive myxoid mesenchymal tumour of infancy: a management paradigm focusing on surgical nuances

Primitive myxoid mesenchymal tumour of infancy (PMMTI) is a rare mesenchymal tumour that typically appears in those under 6 months of age and preferentially affects the deep soft tissues of the trunk and paravertebral spinal regions. PMMTI has only recently been described, and there is scarce literature reporting cases regarding the management paradigm of the tumour. We report the case of an 11-week-old male who presented with bilaterally reduced movement and brisk reflexes in his lower limbs, and irritability. Despite numerous radiological investigations, including MRI, PMMTI was only diagnosed upon biopsy and histopathology. Although PMMTI is known to be relatively unresponsive to chemotherapy, we observed a notable decrease in tumour size after a series of chemotherapy sessions. After two-staged surgical resection of the tumour, the patient is currently stable and under close follow-up. In this article, we aim to report on the patient's clinical presentation, investigations, diagnosis, and treatment, while also discussing the findings from a review of the literature pertaining to future approaches in managing PMMTI. Overall, this case highlights the importance of considering PMMTI in the differential diagnosis of deep soft tissue tumours in young infants and the potential for a combination of chemotherapy and surgical resection to be effective in treating this rare tumour.

Fine needle aspiration cytology of the primitive myxoid mesenchymal tumor of infancy

Primitive myxoid mesenchymal tumor of infancy (PMMTI) is a recently described entity, previously included under the umbrella of undifferentiated sarcomas. These tumors are notorious for recurrence, chemoresistance and may even metastasize. We describe here, for the first time, the cytomorphology of PMMTI. Further, we discuss the morphological differentials and relevant immunocytochemical markers to reach a correct diagnosis. Knowledge about the distinctive cytomorphological features with characteristic immunocytochemistry is the key to the challenging diagnosis of PMMTI. Establishing the diagnosis on cytology is not difficult in cases of recurrence when such a history is forthcoming. These tumors are a rarity, and awareness of cytomorphology and employment of ancillary techniques is diagnostic, guiding the appropriate therapeutic management.

Case report: Local bleomycin injection: A possible treatment option for primitive myxoid mesenchymal tumor of infancy

In recent years, it has been determined that primitive myxoid mesenchymal tumors of infancy (PMMTI) are solid tumors. To date, very few cases of PMMTI have been reported, and there is no consensus regarding treatment. To provide additional references, it is necessary to collect and report the diagnoses and treatment outcomes of related cases. We report the case of a 38-day-old girl who presented with a 5-cm purple tumor in the right shoulder. Upon hospital admission, the patient received an intratumoral injection of bleomycin after diagnosis of a possible lymphangioma. 10 days after the treatment, the tumor began to develop inflammation and necrosis, resulting in a clear demarcation between the tumor and surrounding tissue. Hence, during the second hospitalization, we performed a successful tumor resection. Postoperatively, the tumor was pathologically diagnosed as PMMTI. 3 months after excision, the patient showed no local recurrence on re-examination. To the best of our knowledge, this is the first report of a PMMTI in which bleomycin, or other similar chemotherapeutic drugs, have been injected into tumors. This result offers novel insights into the treatment of PMMTI. Injection therapy with bleomycin and similar chemotherapeutics may result in specific responses to PMMTI, which may help in developing better surgical conditions or improving outcomes in non-surgical patients.

Primitive Myxoid Mesenchymal Tumour of Nose

Primitive Myxoid Mesenchymal Tumour of Infancy (P.M.M.T.I.) is a locally aggressive myofibroblastic tumour, occurring mostly in the first year of life. Grossly, it occurs as a non-encapsulated, multi-nodular tumour with focal infiltrative growth with a size ranging from 2 to 15 cm. It is composed of primitive spindled cells in a myxoid background. It is a low-grade fibroblastic malignancy with low metastatic potential with a high local recurrence rate. On immunohistochemistry, it stains positive for Vimentin. no reactivity for smooth muscle actin, muscle specific actin, desmin, S-100 protein, or myogenin. Electron microscopy documented a poorly differentiated fibroblastic proliferation. The present case is of a P.M.M.T. occurring in the nose of a 3 ½ years old female child. This is the first case reported from Central India. The child had recurrent nasal growth and the excision biopsy was suggestive of intermediate grade fibroblastic neoplasm. The biopsy, on IHC staining, was positive for Vimentin and CD99 and negative for S-100, CD-34 and Desmin, favouring the diagnosis of P.M.M.T. The child had a total of three recurrence of growth after local excision before diagnosis was established. In the prior two surgeries, the histopathological analysis reported it as a benign nasal polyp. After the third surgery, the specimen was sent for IHC. Immunohistochemical stains helped in differentiating it from congenital infantile fibrosarcomas, a similar type of mesodermal tumour. The present case of Primitive myxoid mesenchymal tumour following IHC stains were positive for Vimentin, CD-99, CD-117 and NESTIN, pointing to the primitive nature of the tumour. It was negative for the neural marker. Since it is chemo resistant, the preferred method of treatment is wide surgical excision.

Assessment of BCOR Internal Tandem Duplications in Pediatric Cancers by Targeted RNA Sequencing

Alterations in the BCOR gene, including internal tandem duplications (ITDs) of exon 15 have emerged as important oncogenic changes that define several diagnostic entities. In pediatric cancers, BCOR ITDs have recurrently been described in clear cell sarcoma of kidney (CCSK), primitive myxoid mesenchymal tumor of infancy (PMMTI), and central nervous system high-grade neuroepithelial tumor with BCOR ITD in exon 15 (HGNET-BCOR ITDex15). In adults, BCOR ITDs are also reported in endometrial and other sarcomas. The utility of multiplex targeted RNA sequencing for the identification of BCOR ITD in pediatric cancers was investigated. All available archival cases of CCSK, PMMTI, and HGNET-BCOR ITDex15 were collected. Each case underwent anchored multiplex PCR library preparation with a custom-designed panel, with BCOR targeted for both fusions and ITDs. BCOR ITD was detected in all cases across three histologic subtypes using the RNA panel, with no other fusions identified in any of the cases. All BCOR ITDs occurred in the final exon, within 16 codons from the stop sequence. Multiplex targeted RNA sequencing from formalin-fixed, paraffin-embedded tissue is successful at identifying BCOR internal tandem duplications. This analysis supports the use of anchored multiplex PCR targeted RNA next-generation sequencing panels for identification of BCOR ITDs in pediatric tumors. The use of post-analytic algorithms to improve the detection of BCOR ITD using DNA panels was also explored.

Management of Unresectable Metastatic Primitive Myxoid Mesenchymal Tumor of Infancy: A Case Report and Systematic Review of the Literature

Primitive myxoid mesenchymal tumor of infancy is a rare soft tissue tumor. The present case is one of the most invasive primitive myxoid mesenchymal tumor of infancy reported to date. To our knowledge, it is the first case described with extensive involvement of pelvis and the third described developing metastasis and with an invasion of the spinal canal without evidence of transformation into undifferentiated sarcoma. The patient failed to respond to chemotherapy (CHT). According to the few available data, CHT seems to be more effective in the presence of metastatic disease or increased cellularity. However, CHT, including high-dose ifosfamide, resulted ineffective even after lung metastasis development with pathologic evidence of increased mitotic rate. The management of this case and the data in the literature confirm surgery as the gold standard treatment in this pathology.

Primitive myxoid mesenchymal tumor of infancy with brain metastasis: first reported case

INTRODUCTION

Primitive myxoid mesenchymal tumor of infancy (PMMTI) is a recently diagnosed entity, with only a handful of cases reported to date.

CASE DESCRIPTION

Herein, we present the occurrence of this tumor in a 2-year-old boy, initially diagnosed as primitive neuroectodermal tumor of the extremity and treated with chemotherapy and surgical resection. He later presented with a cerebellar lesion, and biopsy was consistent with PMMTI.

CONCLUSION

While there have been previous cases of PMMTI reported with loco-regional metastatic spread, to our knowledge, there is no known incidence of distant metastasis with involvement of the central nervous system, which makes this case the first of its kind.

Recurrent BCOR internal tandem duplication and BCOR or BCL6 expression distinguish primitive myxoid mesenchymal tumor of infancy from congenital infantile fibrosarcoma

Primitive myxoid mesenchymal tumor of infancy is a rare sarcoma that preferentially affects infants. It can be locally aggressive and rarely metastasizes, but the long-term outcome of children with this tumor is mostly unknown. Histologically, it is characterized by primitive cells with abundant myxoid stroma. Internal tandem duplication of B-cell CLL/lymphoma 6 (BCL6)-interacting co-repressor (BCOR) exon 15 has recently been described in clear cell sarcoma of kidney, central nervous system high-grade neuroepithelial tumor with BCOR alteration, and primitive myxoid mesenchymal tumor of infancy. Herein, we report five cases of primitive myxoid mesenchymal tumor of infancy: three girls and two boys with mean age of 6.5 months. The tumors were located in the paraspinal region (n=3), back (n=1), or foot (n=1) and ranged in size from 2.5 to 10.2 cm. BCOR internal tandem duplication was confirmed by PCR and sequencing in all five cases. The minimally duplicated region consisted of nine residues, which is shorter than was previously reported in other BCOR-associated tumors. To assess the clinical value and specificity of the BCOR internal tandem duplication, a group of 11 ETV6-rearranged congenital infantile fibrosarcomas were evaluated and no BCOR internal tandem duplication was identified in any case. Though not detected in congenital infantile fibrosarcomas, BCOR and BCL6 immunoreactivity was present in >90% of the nuclei of tumor cells in each of the five primitive myxoid mesenchymal tumor of infancy. The presence of BCOR internal tandem duplication in all five primitive myxoid mesenchymal tumors of infancy provides evidence that it is a recurrent somatic abnormality and substantiates the concept that this tumor is a unique sarcoma of infancy. Our findings indicate that identification of BCOR internal tandem duplication and/or nuclear immunoreactivity for BCOR or BCL6 can aid in the diagnosis of primitive myxoid mesenchymal tumor of infancy and help to differentiate it from congenital infantile fibrosarcoma.

Primitive Myxoid Mesenchymal Tumor of Infancy Involving Chest Wall in an Infant: A Case Report and Clinicopathologic Correlation

Primitive myxoid mesenchymal tumor of infancy (PMMTI) is a rare mesenchymal tumor of early childhood characterized by aggressive local infiltration of surrounding structures, rare metastases, and poor response to chemotherapy. Surgery alone appears to be the most effective treatment given the lack of predilection for metastasis and poor response to traditional chemotherapy. Below we report a patient with PMMTI successfully managed with surgery and observation and summarize the existing literature on histopathologic features and treatment of this lesion.

Undifferentiated myxoid lipoblastoma with PLAG1-HAS2 fusion in an infant; morphologically mimicking primitive myxoid mesenchymal tumor of infancy (PMMTI)--diagnostic importance of cytogenetic and molecular testing and literature review

Lipoblastoma is a benign myxoid neoplasm arising in young children that typically demonstrates adipose differentiation. It is often morphologically indistinguishable from primitive myxoid mesenchymal tumor of infancy (PMMTI), which is characterized by a well-circumscribed myxoid mass with a proliferation of primitive mesenchymal cells with mild cytologic atypia. PMMTI occurs in the first year of life and is known to have locally aggressive behavior. No specific genetic rearrangements have been reported to date. In contrast, the presence of PLAG1 (Pleomorphic Adenoma Gene 1) rearrangement is diagnostic for lipoblastoma. We hereby demonstrate the combined application of multiple approaches to tackle the diagnostic challenges of a rapidly growing neck tumor in a 3-month-old female. An incisional tumor biopsy had features of an undifferentiated, myxoid mesenchymal neoplasm mimicking PMMTI. However, tumor cells showed diffuse nuclear expression by immunohistochemical (IHC) stain. Conventional cytogenetic and fluorescence in situ hybridization (FISH) analyses as well as next generation sequencing (NGS) demonstrated evidence of PLAG1 rearrangement, confirming the diagnosis of lipoblastoma. This experience warrants that undifferentiated myxoid lipoblastoma can mimic PMMTI, and the combination of cytogenetic and molecular approaches is essential to distinguish these two myxoid neoplasms. Literature on lipoblastomas with relevant molecular and cytogenetic findings is summarized. Our case is the first lipoblastoma diagnosed with a PLAG1 fusion defined by NGS technology.

Transformation of a primitive myxoid mesenchymal tumor of infancy to an undifferentiated sarcoma: a first reported case

An 8-month-old girl underwent surgical resection of a cervical mass with histologic diagnosis of a primitive myxoid mesenchymal tumor of infancy (PMMTI). More than 5 years after the initial surgical intervention, the tumor recurred locally, with numerous distant metastases. The histologic morphology of this tumor was compatible with a diagnosis of an undifferentiated high-grade sarcoma. PMMTI is a recently described poorly differentiated fibroblastic soft-tissue tumor of infancy, of at least borderline biological behavior, characterized by local recurrence and a potential to metastasize. We present here the first case of a transformation of a PMMTI into an undifferentiated high-grade sarcoma.

Primitive Myxoid Mesenchymal Tumor of Infancy With Rosettes

Primitive myxoid mesenchymal tumor of infancy (PMMTI) is a relatively recently described tumor arising in infants and demonstrating a unique histomorphology. We present an unusual case of PMMTI with rosettes, a hitherto undescribed finding in the reported cases. We also present the cytogenetic and ultrastructural findings of this tumor and review the literature. As awareness of PMMTI increases, additional clinical data and histopathologic findings will aid in the morphologic and behavioral characterization of this neoplasm.

A rare malignant tumor of scalp in a 3-month-old Taiwanese infancy: case report of primitive myxoid mesenchymal tumor of infancy with molecular study

Primitive myxoid mesenchymal tumor of infancy is an extremely rare and recently recognized soft tissue tumor entity with a tendency for multiple recurrences. Only ten cases have been described in the literature and most cases are reported in Western countries. This tumor ranges in size from 2 to 15 cm and is characterized microscopically by a diffuse growth of primitive cells in a myxoid background with focal fascicles or a herringbone pattern. In this study, we describe a primitive myxoid mesenchymal tumor of infancy on the scalp of a 3-month-old Taiwanese boy. The histology showed typical morphology and the tumor cells showed vimentin and CD99 immunoreactivities. The translocation t(12,15)(p13;q25) was not found by fluorescence in situ hybridization. After complete surgical excision, no recurrence was noted during an 18-month follow-up.