Table of Contents
Definition / general | Clinical features | Prognostic factors | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Molecular / cytogenetics images | Differential diagnosisCite this page: Arora K. Inflammatory myofibroblastic tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueinflammyofibro.html. Accessed January 20th, 2021.
Definition / general
- Tumor of myofibroblasts with plasma cells, lymphocytes and eosinophils
- Also called inflammatory fibrosarcoma, inflammatory pseudotumor, plasma cell granuloma
- See also discussions in these chapters: Bladder, Breast, Colon tumor, Eye (orbit), Liver, Lung, Lymph node, Small bowel, Thyroid gland
- Retroperitoneum (omentum) and mesentery in children and young adults (mean age 10 years)
- Also lung, GI, GU, other sites
Clinical features
- 1/3 have associated fever, growth failure, malaise, weight loss, anemia, thrombocytosis, polyclonal hyperglobulinemia and elevated sedimentation rate
- Symptoms disappear after excision of mass (J Korean Med Sci 2002;17:699)
Prognostic factors
- Poor
- Abdominal or pelvic sites, ALK negative (Am J Surg Pathol 2007;31:509)
Case reports
- 4 year old boy with fever, colicky epigastric pain and lower midline abdominal lesion (Case of the Week #400)
- 6 year old boy with abdominal wall tumor (Surg Today 2007;37:352)
- 7 year old girl whose abdominopelvic tumor has t(1;2)(q21;p23) (Arch Pathol Lab Med 2006;130:1042)
- 18 year old man with omental tumor and bone marrow involvement (Arch Pathol Lab Med 2003 Jul;127:865)
- 46 year old woman with retroperitoneal tumor (World J Surg Oncol 2005;3:66)
- 63 year old man with mesenteric tumor (World J Gastroenterol 2007;13:3645)
Treatment
- Excision (J Pediatr Surg 2005;40:1581)
- 25 - 35% recur, rare metastases (or may be evidence of multifocality)
Gross description
- Circumscribed, not encapsulated
- White tan mass with whorled fleshy or myxoid cut surface
- May have focal hemorrhage, necrosis or calcification, mean 6 cm
Gross images
Microscopic (histologic) description
- Myofibroblastic and fibroblastic spindle cells with inflammatory infiltrate of lymphocytes, plasma cells, eosinophils, histiocytes
- Background of abundant blood vessels
- Mixture of three patterns:
- Resembling nodular fasciitis with elongated myofibroblasts containing abundant eosinophilic cytoplasm and vesicular nuclei, loose myxoid stroma with neutrophils, lymphocytes and eosinophils, but few plasma cells;
- Cellular with spindled myofibroblasts and fibroblasts in more compact stroma, arranged as islands surrounded by fibromyxoid stroma with prominent plasma cells and mitotic figures;
- Densely hyalinized stroma with few spindle cells, few plasma cells or lymphocytes
- May have ganglion-cell like myofibroblasts
- All 3 patterns have no nuclear pleomorphism, no atypical mitotic figures
- Malignant behavior: associated with highly atypical polygonal cells with oval nuclei, prominent nucleoli, Reed-Sternberg like cells, atypical mitotic figures
Microscopic (histologic) images
Case #400 - epithelioid inflammatory myofibroblastic sarcoma (EIMS):
Contributed by Mark R. Wick, M.D.
AFIP images
Images hosted on other servers:
Positive stains
- Vimentin (diffuse, strong), usually alpha smooth muscle actin, muscle specific actin and calponin (Hum Pathol 2008;39:846)
- ALK1 / p80 in 40%, but not specific (Mod Pathol 2002;15:931)
- Keratin and desmin in 1/3
Negative stains
Electron microscopy description
- Myofibroblastic cells and activated fibroblasts
Molecular / cytogenetics description
- Clonal abnormalities of 2p23 (Cancer Res 1999;59:2776) including t(2;5)(p23;q35) involving ALK and NPM
- Also t(2;17)(p23;q23) involving ALK and CLTC (Am J Pathol 2001;159:411) and t(2;19)(p23;p13.1) involving ALK and TPM4 (Am J Pathol 2000;157:377)
- Associated with ALK deregulation and younger patients
- See Atlas of Genetics
Molecular / cytogenetics images
Differential diagnosis
- Calcifying fibrous pseudotumor: calcification, no myofibroblastic proliferation, actin negative (Mod Pathol 2001;14:784)
- IgG4 related sclerosing lesion: IgG4+ plasma cells and the ratio of IgG4+ / IgG+ plasma cells is lower in IMT
- Low grade myofibroblastic sarcoma: more uniform appearance with higher cellularity, more prominent hyperchromasia, more infiltrative, ALK (Hum Pathol 2008;39:846)
- Nodular fasciitis: smaller size, older patients, less inflammation
- The presence of obstructive phlebitis
- Absence of ALK (Mod Pathol 2011;24:606, Am J Surg Pathol 2009;33:1330)