# Clinicopathological Features and Immunochemical Staining of Inflammatory Myofibroblastic Tumor: A Retrospective Study of 48 Cases

## TL;DR

This study examines the clinicopathological features and immunochemical profiles of 48 inflammatory myofibroblastic tumor cases to improve diagnosis and understanding of the disease.

## Contribution

The study provides new insights into the diagnostic challenges of ALK-negative inflammatory myofibroblastic tumors through a detailed retrospective analysis.

## Key findings

- ALK positivity was observed in 12 out of 48 cases, with no significant correlation to age, sex, or tumor site.
- Smooth muscle actin was positive in 74.5% of cases, while S-100, CD34, CD117, myogenin, and DOG1 were consistently negative.
- ALK-negative tumors tended to occur in nonvisceral organs like the head, neck, extremities, and genitals.

## Abstract

Inflammatory myofibroblastic tumors (IMTs) are rare neoplasms found in diverse anatomical sites, including the lungs, intestines, and bladder. Surgical resection is the primary treatment, with chemotherapy offering survival rates of 21.2 and 42.5 months in unresectable cases. Anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors (TKIs) have emerged as standard treatments. However, IMT presents diagnostic challenges owing to its morphological similarities with other conditions. While positive ALK expression aids diagnosis in approximately 50% of the cases, negative ALK expression complicates diagnosis. This retrospective study reviewed 48 patients with IMT diagnosed at a Taiwanese medical center and analyzed their clinical characteristics, pathology reports, immunohistochemical (IHC) staining profiles, and outcomes. Chi‐square and independent t‐tests were used for the statistical analysis. The results showed an equal sex distribution, with the gastrointestinal tract being the most prevalent site, followed by the urinary system and lungs. Positive ALK expression was observed in 12 patients. While no statistically significant differences were found between ALK expression and age, sex, or site of occurrence, a younger mean age was noted in the ALK‐positive group, which is consistent with the existing literature. Moreover, ALK negativity tended to occur in the nonvisceral organs (head and neck, extremities, and genitals). Regarding IHC staining, smooth muscle actin (SMA) was positive in 74.5% of cases, whereas S‐100 protein, CD34, CD117, myogenin, and DOG1 were consistently negative. For desmin and cytokeratin, the results differed among cases and may not be used as determinant factors to diagnose such diseases. We hope that this investigation will be a cornerstone for further studies on the diagnosis of IMT in the absence of ALK rearrangements.