Inflammatory myofibroblastic tumor pathology

Introduction

Inflammatory myofibroblastic tumor (IMT) rarely appears on the skin as slow growth dermal tumor. Many tumors show translocation of the ALK gene. Some of these tumors were labeled as' pseudotumors' or 'plasma cell granuloma' in the past.

Histology of inflammatory myofibroblastic tumor

Histologically, the injury is based on the dermis and seen underlying a normal epidermis (Figure 1). The tumor is made up of a mixture of ovoid and spindle-shaped cells with a prominent inflammatory infiltrate (Figures 2–3). The infiltrate is characteristically rich in plasma cells (best seen in Figure 2). There may be some pleomorphism of tumor cells and some mitotic figures (figure 3, arrow).

Special stains for inflammatory myofibroblastic tumor

Tumor cells stain strongly with vimentin and variably with smooth muscle markers. SMA is positive in up to 90% cases. ALK (anaplastic lymphoma kinase) immunohistochemistry it is seen in most cases and when seen it is practically diagnostic in the correct context. FISH Tests for ALK gene rearrangements can also be used.

Differential diagnosis of inflammatory myofibroblastic tumor pathology

Various inflammatory mesenchymal tumors: Pleomorphic sarcomas, melanomaand leiomyosarcoma have inflammatory variants. ALK positivity by FISH immunohistochemistry can be useful in difficult cases.

Pseudotumor and Plasma Cell Granuloma: Unimportant atypia and ALK gene translocations. Many IMTs have been labeled as pseudotumors in the past.