Surgical Pathology Criteria

Inflammatory Myofibroblastic Tumor

Differential Diagnosis

Sclerosing Inflammatory Lesions (Retroperitonitis, Mesenteritis, Mediastinitis, Cholangitis, Pancreatitis) Inflammatory Myofibroblastic Tumor
Diffuse, typically no distinct mass Circumscribed mass lesion
Rare in children Usually in children
IgG4 serum levels and plasma cells increased No association with IgG4


Inflammatory Myofibroblastic Tumor Nodular Fasciitis
Frequently over 5 cm Rarely over 5 cm
Usually in children Rare in children
Frequently involves abdominal cavity Does not involve abdominal cavity
Variable patterns Usually loose pattern throughout
Prominent inflammatory cells Only scattered inflammatory cells


Inflammatory Myofibroblastic Tumor Infantile Fibromatosis
Frequent in abdomen Rare in abdomen
Usually age 0-14 years Age <5 years
Prominent inflammation Variable, peripheral inflammation
Variable locations Centered in muscle


Fibromatosis, Abdominal Desmoid, Extra-abdominal Desmoid, Mesenteric, Retroperitoneal and Pelvic Inflammatory Myofibroblastic Tumor
Rare <12 years of age Age usually <14, rare >30
Inflammation not prominent Prominent inflammation, particularly plasma cells
Alk1 negative Alk1 frequently positive
Beta catenin 80-90% Beta catenin negative


Inflammatory Myofibroblastic Tumor Gastrointestinal Stromal Tumor
Usually in children Rare in children
Frequently associated with systemic signs and symptoms Not associated with systemic signs and symptoms
Prominent inflammatory cells Usually only scattered inflammatory cells
Frequently positive for desmin, keratin and ALK Desmin, keratin and ALK negative
CD117, DOG1, CD34 negative CD117 74-95%, DOG1 87-95%, CD34 70%


Inflammatory Fibroid Polyp Inflammatory Myofibroblastic Tumor
Systemic signs and symptoms absent Systemic signs and symptoms frequent
Infrequent involvement of muscularis propria Frequent involvement of muscularis propria
Eosinophils predominate Plasma cells usually predominate
Concentric onion skin like pattern around vessels and glands is frequent Lacks concentric onion skin pattern
Not associated with lymphadenopathy May have reactive regional lymphadenopathy


Inflammatory Myofibroblastic Tumor Leiomyosarcoma of Soft Tissue
Usually <14 years, rare >30 years Rare under 12 years
Chronic inflammation usual Infrequent inflammation
Rare inflammatory leiomyosarcoma exhibits a regular fascicular pattern


Inflammatory Malignant Fibrous Histiocytoma Inflammatory Myofibroblastic Tumor
Mean age 50, wide range Usually <14 years, rare >30 years
Sheets of neutrophils Mixed or lymphocyte predominant inflammation
Marked cytologic atypia Absent or mild atypia


Myofibroma Inflammatory Myofibroblastic Tumor
90% <2 years Usually age 0-14 years
Biphasic nodules with immature cells No immature cells
Hemangiopericytomatous vessels No HPC like vessels
Rare in abdomen Frequent in abdomen


Dedifferentiated Liposarcoma Inflammatory Myofibroblastic Tumor
High grade nonlipogenic comoponent present Lacks significant cytologic atypia
Atypical lipomatous tumor component present Lacks lipomatous component


Inflammatory Myofibroblastic Tumor Inflammatory Pseudotumor of Lymph Node and Spleen
ALK positive 35-60% ALK negative
EBV negative EBV may be positive
Rare in lymph node and spleen Occurs in lymph node and spleen


In the GU tract some consider the following to be separate entities while others consider them to be the same lesion
Inflammatory Myofibroblastic Tumor Pseudosarcomatous Myofibroblastic Proliferation of GU Tract
Prominent lymphoplasmacytic infiltrate Lacks prominent plasma cells
Frequent storiform and fibrous areas Lacks storiform and fibrous areas
Pale eosinophilic cytoplasm on spindle cells Intensely eosinophilic cytoplasm on spindle cells
Both may be postive for actin, desmin, keratin, ALK and both are benign at this site


Inflammatory Myofibroblastic Tumor Follicular Dendritic Cell Neoplasm
Rarely involves lymph node or spleen Frequently involves lymph node and spleen
ALK positive 35-60% ALK negative
CD21, CD23, CD35 negative CD21, CD23 or CD35 positive
EBV negative EBV positive by in situ hybridization


Inflammatory Myofibroblastic Tumor Interdigitating Dendritic Cell Sarcoma
ALK positive 35-60% ALK negative
S100 negative S100 positive


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