A Giant Thoracic ALK-Rearranged Mesenchymal Neoplasm in a Child - Case Report

Sep 23, 2026

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Mesenchymal neoplasms with ALK fusions mainly include inflammatory myofibroblastic tumors and epithelioid fibrous histiocytomas, while rarer ALK-rearranged mesenchymal tumors show S100 and CD34 coexpression and broader clinicopathological behavior. An 11-year-old girl with a giant left thoracic cavity mass underwent thoracoscopic resection; pathology revealed spindle-cell fascicular growth, necrosis, S100/CD34 coexpression, and PLEKHH2::ALK fusion by NGS. Despite overt malignant features, brain metastasis after surgery responded well to alectinib.

LanguageEnglish

CategoryHealthcare

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Pages6

Reading Time15 min

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Abstract

Introduction

ALK and ALK-fusion mesenchymal tumors

Case Presentation

Clinical presentation and pathology

Treatment and follow-up

Cancer Reports CASE REPORT OPEN ACCESS A Giant Thoracic ALK-Rearranged Mesenchymal Neoplasm in a Child Sheng Gao1 | Junhua Wu1 | Jun Fan1 | Xiaona Chang1 | Bo Huang1 | Danju Luo1 | Jun He1 | Heshui Shi2 | Xiaochuan Dong1 | Xiu Nie1 1Department of Pathology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China | 2Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China Correspondence: Xiaochuan Dong ([xiaochuanhust@163.com](xiaochuanhust@163.com)) | Xiu Nie ([whunhpath@163.com](whunhpath@163.com)) Received: 24 August 2025 | Revised: 7 December 2025 | Accepted: 3 February 2026 Keywords: alectinib | ALK-rearranged mesenchymal neoplasm | PLEKHH2::ALK fusion | thoracic ABSTRACT Background: Mesenchymal neoplasms characterized by ALK fusions mainly include inflammatory myofibroblastic tumors (IMTs) and epithelioid fibrous histiocytomas (EFHs) . More recently, ALK-rearranged mesenchymal tumors that are not IMTsor EFHs, characterized by S100 and CD34 coexpression, have been reported in a few small series and isolated case reports. The neoplasms present a broad clinicopathological spectrum and variable biological behavior. Case Presentation: Here, we report the case of an 11-year-old girl with a giant mesenchymal neoplasm in her left thoracic cavity. Pathological biopsy revealed that the tumor was composed of monomorphic spindle cells arranged in a fascicular growth pattern with extensive necrosis and coexpression of S100 and CD34; subsequently, PLEKHH2::ALK fusion was identified via next-generation sequencing (NGS). The patient underwent tumor resection via thoracoscopy. The specimen from radical resection indicated that the tumor was heterogeneous. Some tumor cells showed moderate to severe atypia with increased mitosis and necrosis, suggesting that the neoplasm had overtly malignant features and may be associated with an aggressive clinical course. The patient developed brain metastasis 3 months after surgery and subsequently responded well to targeted therapy with the ALK inhibitor alectinib. Conclusions: Our findings indicate thatALK-rearranged mesenchymal neoplasms with fibrosarcoma-like features, particularly those associated with elevated mitotic activity or tumor necrosis, should be classified as high grade in pathology reports. In addition, this case also demonstrated that neoadjuvant therapy may be a better treatment strategy compared to upfront surgery for ALK-rearranged mesenchymal neoplasms with a relatively high tumor burden. 1 | Introduction The anaplastic lymphoma kinase (ALK) gene, located at chromosomal band 2p23, encodes a receptor tyrosine kinase (RTK) proto-oncogene. The ALK fusion protein is predominantly activated through genetic rearrangements, leading to its constitutive expression and subsequent induction of oncogenic transformation [1–6] . The subsets of mesenchymal tumors harboring ALK fusions mainly include inflammatory myofibroblastic tumors (IMTs), epithelioid inflammatory | Abbreviations: ALK, anaplastic lymphoma kinase; CT, computed tomography; EFHs, epithelioid fibrous histiocytomas; EIMSs, epithelioid inflammatory myofibroblastic sarcomas; FISH, fluorescence in situ hybridization; FNCLCC, Federation of Cancer Centers Sarcoma Group; HPFs, high-power fields; IMTs, inflammatory myofibroblastic tumors; MFs, mitotic figures; MPNST, malignant peripheral nerve sheath tumor; MRI, magnetic resonance imaging; NGS, nextgeneration sequencing; PD, progressive disease; PR, partial response.
Sheng Gao, Junhua Wu, and Jun Fan contributed equally to this study. | | --- | | This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
© 2026 The Author(s). Cancer Reports published by Wiley Periodicals LLC.

FAQs

What genetic alteration was identified in the child’s tumor?

Next-generation sequencing identified a PLEKHH2::ALK fusion in the tumor after biopsy and immunophenotypic assessment.

How was the tumor managed initially, and what additional therapy was used?

The patient underwent tumor resection via thoracoscopy. After brain metastasis developed 3 months post-surgery, the patient responded well to targeted therapy with the ALK inhibitor alectinib.

What pathological features supported a high-grade classification?

The resected tumor showed extensive necrosis and areas with moderate to severe atypia, increased mitosis, and overt malignant features, leading to the authors’ emphasis on high-grade classification when aggressive features are present.

Sep 23, 2026

Uploaded by Hazel