Foreign body granulomas typically present as a tender mass 1.
Granulatmous reactions aim to either resorb organic (e.g. wood,) or sequester inorganic (e.g. metal, glass) foreign bodies. If the foreign body completely resorbed the granulomatous reaction ceases but if not a capsule forms around the foreign body with the immune reaction often becoming inactive. If there is damage to the capsule then the granulomatous reaction, and possibly symptoms, recurs 2.
Lesion morphology can vary widely and depends on the material, size and location of the foreign body 1.
High frequency (>10 MHz) linear probe is useful 1:
- foreign bodies typically appear echogenic with posterior acoustic shadowing
- foreign body granuloma appears as a hypoechoic halo that can consist of hematoma, edema and/or granulation tissue
A long-standing foreign body granuloma will have a capsule with the following signal characteristics 2:
- T1: low signal
- T2: low signal
- T1C+: linear enhancement
- foreign body granulomas have been misdiagnosed as soft tissue tumors when a foreign body is not seen or recognized 1
- 1. Ando A, Hatori M, Hagiwara Y, Isefuku S, Itoi E. Imaging features of foreign body granuloma in the lower extremities mimicking a soft tissue neoplasm. (2009) Upsala journal of medical sciences. 114 (1): 46-51. doi:10.1080/03009730802602455 - Pubmed
- 2. Carneiro BC, Cruz IAN, Chemin RN, Rizzetto TA, Guimarães JB, Silva FD, Junior CY, Pastore D, Ormond Filho AG, Nico MAC. Multimodality Imaging of Foreign Bodies: New Insights into Old Challenges. (2020) Radiographics : a review publication of the Radiological Society of North America, Inc. 40 (7): 1965-1986. doi:10.1148/rg.2020200061 - Pubmed