Mesenchymal PLAG1 Tumor With PCMTD1-PLAG1 Fusion in an Infant: A New Type of “Plagoma”

Abstract

In the past decade, there have been major advances in knowledge related to mesenchymal tumors, and new genetic alterations are being delineated. We report a mesenchymal spindle cell neoplasm harboring a novel gene fusion in an infant. Histopathologically, the neoplasm shared some features with sclerosing perineurioma, but immunohistochemically, EMA was negative, whereas GLUT1, NK1-C3, and BCOR were positive. Next-generation sequencing revealed a PCMTD1-pleomorphic adenoma gene 1 (PLAG1) fusion. PLAG1 contributes to the expression of a variety of genes implicated in regulating cell proliferation, and PCMTD1 has been related to the development of certain carcinomas. Recently, other soft tissue tumors in young children associated with PLAG1 fusion variants have been reported. Perhaps, mesenchymal neoplasms presenting PLAG1 fusions with different genes would confirm a specific group (PLAG mesenchymal tumours or "plagomas") in the near future.

Pediatric fibromyxoid tumor with PLAG1 fusion: An emerging entity with a novel intracranial location

“…It is true that we cannot rule out a pathogenetic relationship of our case to lipoblastoma. Nevertheless, we do not feel there is convincing evidence that our case is related to lipoblastoma or any other adipocytic tumor and, instead, we feel it is another example of a distinct tumor phenotype, similar to the six tumors recently documented in soft tissue 8–11 . The term “PLAG1 mesenchymal tumors” has been suggested 10 .…”

“…Mitotic rates were low and Ki‐67 indices, when reported, were ≤ 5%. Although none showed a distinctive immunoprofile, all but one case 10 expressed CD34 and desmin, at least focally. Individual cases also expressed other markers, including S‐100 protein, GFAP, BCOR, CD10, CD117, GLUT1, and EMA.…”

“…7,15,29,32 Recently, six cases have been reported of soft tissue tumors with a PLAG1 fusion, showing a fibroblastic or mixed fibroblastic and myxoid morphology but no other lines of differentiation (summarized in Table 1). [8][9][10] We include in this group one case of a tumor called a "fibroblastic lipoblastoma" but which lacked adipocytic differentiation. 11 The partner genes for these tumors include YWHAZ (2 cases), EEF1A1, ZFHX4l, CHCHD7, and PCMTD1 (two cases).…”

“…but no other lines of differentiation. They are typically immunopositive for desmin and CD34 8–10 . The partner genes for these tumors have included YWHAZ , EEF1A1 , ZFHX4l , CHCHD7 , and PCMTD1 .…”

“…They are typically immunopositive for desmin and CD34. [8][9][10] The partner genes for these tumors have included YWHAZ, EEF1A1, ZFHX4l, CHCHD7, and PCMTD1. Opinion is divided over whether these tumors are a specific entity or simply related to lipoblastoma since many of the gene fusions have also been reported for that entity.…”