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 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.

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.