A Case Report of Anaplastic Lymphoma Kinase-Negative Inflammatory Myofibroblastic Tumor in the Anterior Mediastinum of an Elderly Male

Summary

An older male patient with an anaplastic lymphoma kinase-negative inflammatory myofibroblastic tumor in the anterior mediastinum achieved favorable disease control after complete surgical resection and remained recurrence-free during 2 years of follow-up.

Abstract

Inflammatory myofibroblastic tumor (IMT) is an uncommon mesenchymal neoplasm of intermediate biological potential, characterized by proliferating myofibroblastic spindle cells with a prominent inflammatory infiltrate. Although IMT occurs more commonly in children and young adults, primary involvement of the anterior mediastinum is exceedingly rare, particularly in older male patients, and may mimic more common anterior mediastinal tumors such as thymoma or thymic carcinoma. The authors report on a 68-year-old male patient with an incidentally detected anterior mediastinal mass. Contrast-enhanced chest computed tomography and magnetic resonance imaging revealed a 6.6 × 3.6-cm anterior mediastinal soft-tissue lesion with heterogeneous enhancement, peripheral delayed enhancement, central hypoenhancement, restricted diffusion, and an indistinct interface with adjacent pericardial structures. The patient underwent complete surgical resection via median sternotomy. Histopathological examination showed spindle-cell proliferation with a prominent lymphoplasmacytic infiltrate, supporting the diagnosis of IMT. Immunohistochemistry showed anaplastic lymphoma kinase (ALK) negativity. Additional ancillary studies showed negative staining for CD21, CD23, and CXCL13 and negative Epstein–Barr virus (EBV)-encoded small RNA in situ hybridization, arguing against follicular dendritic cell sarcoma and EBV-associated lesions. Fluorescence in situ hybridization showed no rearrangements involving ALK, ROS1, RET, or PDGFRB. The patient recovered well without adjuvant therapy, postoperative CA125 and neuron-specific enolase levels returned to the normal range, and no recurrence or metastasis was observed during 2 years of follow-up. This rare case highlights that ALK-negative anterior mediastinal IMT should be considered in the differential diagnosis of anterior mediastinal masses across age groups. Complete resection may provide durable disease control in selected resectable cases, but the single-case nature of this report and the known recurrence potential of IMT support cautious interpretation and long-term surveillance.

Introduction

Inflammatory myofibroblastic tumor (IMT) is an uncommon mesenchymal neoplasm composed of spindle-shaped fibroblastic or myofibroblastic cells accompanied by a variable chronic inflammatory infiltrate, most commonly plasma cells and lymphocytes, with occasional eosinophils and mast cells^1,2. According to the latest World Health Organization (WHO) classification, IMT is recognized as a tumor of intermediate biological potential rather than a purely reactive inflammatory lesion³. In the 2002 WHO classification of soft-tissue tumors, the term ‘inflammatory myofibroblastic tumor’....

Protocol

1. Ethics statement and patient consent

This case report was reviewed and approved by the Ethics Committee of Shengli Oilfield Central Hospital (Approval No. YXLL202504301). The Ethics Committee waived the requirement for written informed consent because all patient information was anonymized and no identifying information was included in the publication. All patient-identifying information has been removed from the clinical, imaging, intraoperative, and histopathological materials presented in this report.

2. Surgical resection procedure

1. On March 10, 2022, the patient ....

Results

The following outcomes were obtained by executing the described protocol. The procedure successfully achieved complete macroscopic resection of the anterior mediastinal mass. Histopathological analysis of the resected specimen supported the final diagnosis of IMT. Histological examination results: Microscopic evaluation of HE-stained sections revealed spindle-shaped tumor cells arranged in fascicles or a storiform pattern. The cells exhibited abundant eosinophilic cytoplasm and round-to-oval nuclei with mild atypia. The .......

Discussion

Inflammatory myofibroblastic tumor is a rare mesenchymal tumor composed predominantly of spindle-shaped myofibroblastic or fibroblastic cells accompanied by a variable inflammatory infiltrate¹⁵. The pathogenesis of IMT has not been fully elucidated despite its histological features being relatively well defined. Chronic inflammatory stimulation has been proposed as one potential contributor to tumor development, but IMT is now generally regarded as a true neoplasm rather than a purely reactive inf.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
10% neutral buffered formalin	Guangzhou Weiges Biotechnology Co., Ltd.	5200015	Used for fixation of the resected tumor specimen.
ALK antibody	Fuzhou Maixin Biotech Co., Ltd.	MAB-0281	Clone ALKp80 (5A4); ready-to-use; used for ALK immunohistochemistry.
Automated H&E staining system	Roche Diagnostics/Ventana Medical Systems	VENTANA HE 600	Used for automated hematoxylin and eosin staining.
Automated IHC staining platform	Roche Diagnostics/Ventana Medical Systems	VENTANA BenchMark ULTRA	Used for immunohistochemical staining.
Automated tissue processor	Thermo Scientific/Epredia	A82300001	Used for dehydration, clearing, and paraffin infiltration of fixed tissue.
β-catenin antibody	Fuzhou Maixin Biotech Co., Ltd.	MAB-0754	Clone MX043; ready-to-use; used to assess β-catenin expression.
Buffer solution	Roche Diagnostic Products (Suzhou) Co., LTD	86187	Used to maintain the appropriate pH during automated staining procedures.
Cardiac ultrasound system	Philips	EPIQ 7C	Used for preoperative cardiac ultrasonography to evaluate the anterior mediastinal mass and its relationship to the right ventricle.
CD117 antibody	Fuzhou Maixin Biotech Co., Ltd.	Kit-0029	Clone YR145; ready-to-use; used to exclude KIT-positive tumors.
CD21 antibody	Fuzhou Maixin Biotech Co., Ltd.	RMA-1030	Clone MXR015; ready-to-use; used to exclude KIT-positive tumors.
CD23 antibody	Fuzhou Maixin Biotech Co., Ltd.	RMA-0504	Clone SP23; ready-to-use; used to exclude KIT-positive tumors.
CD35 antibody	Fuzhou Maixin Biotech Co., Ltd.	RM-0768	Clone EP197; ready-to-use; used to evaluate CD35 expression and assist in differential diagnosis.
CD68 antibody	Fuzhou Maixin Biotech Co., Ltd.	Kit-0026	Clone KP1; ready-to-use; used to evaluate histiocytic/macrophage-associated staining.
CT scanner	Siemens AG	SOMATOM Force CT	Used for contrast-enhanced chest CT evaluation of the anterior mediastinal mass.
CXCL13 antibody	Fuzhou Maixin Biotech Co., Ltd.	MAB-1007	Clone MX107; ready-to-use; used to evaluate CD35 expression and assist in differential diagnosis.
Decolorizing solution	Roche Diagnostic Products (Suzhou) Co., LTD	86184	Used for deparaffinization/decolorization during automated H&E staining.
EMA antibody	Fuzhou Maixin Biotech Co., Ltd.	Kit-0011	Clone E29; ready-to-use; used to evaluate epithelial membrane antigen expression.
Eosin staining solution VENTANA HE 600 Eosin	Ventana Medical Systems	86183	Used for cytoplasmic and extracellular matrix staining during automated H&E staining.
Glass cover slip	Ventana Medical Systems	86188	Used to cover stained tissue sections for microscopic examination.
Hematoxylin staining solution VENTANA HE 600 Hematoxylin	Ventana Medical Systems	86189	Used for nuclear staining during automated H&E staining.
Ki-67 antibody	Fuzhou Maixin Biotech Co., Ltd.	RMA-0731	Clone MXR002; ready-to-use; used to estimate the tumor proliferation index.
Microtome	Leica Biosystems	149BIO000C1	Used to cut 4–5 μm paraffin sections.
MRI system	Siemens AG	MAGNETOM Trio Tim 3.0T MRI	Used for contrast-enhanced chest MRI and diffusion-weighted imaging.
Pan-Cytokeratin antibody	Fuzhou Maixin Biotech Co., Ltd.	Kit-0009	Clone AE1/AE3; ready-to-use; used to exclude epithelial tumor differentiation.
Paraffin wax	Fujian Weiao Medical Equipment Co., Ltd.	WP-58/60	Used for embedding processed tissue specimens.
Recoloring dye solution	Roche Diagnostic Products (Suzhou) Co., LTD	86185	Used as an auxiliary staining reagent to improve contrast during automated H&E staining.
S-100 antibody	Fuzhou Maixin Biotech Co., Ltd.	RMA-1075	Clone MXR0347; ready-to-use; used to exclude neural or melanocytic differentiation.
Sample preservation solution VENTANA HE 600 Coverslip Activator	Ventana Medical Systems	86181	Used during the automated coverslipping process.
Smooth Muscle Actin antibody	Fuzhou Maixin Biotech Co., Ltd.	Kit-0006	Clone 1A4; ready-to-use; used to evaluate smooth muscle/myofibroblastic differentiation.
VENTANA HE 600 Cleaning Solution	Roche Diagnostic Products (Suzhou) Co., LTD	86190	Used for routine cleaning and maintenance of the VENTANA HE 600 system. Please verify the exact product name from the reagent label.
VENTANA HE 600 Coverslip Activator (2-Pack)	Ventana Medical Systems	86186	Used during the automated coverslipping process on the VENTANA HE 600 system.
VENTANA HE 600 Wash	Roche Diagnostic Products (Suzhou) Co., LTD	86182	Used for washing slides during the automated H&E staining process.
Vimentin antibody	Fuzhou Maixin Biotech Co., Ltd.	MAB-0735	Clone MX034; ready-to-use; used to evaluate mesenchymal differentiation.