Friday, July 9, 2010

Ants and a Shoulder Mass

Photo by TillinKa

A surgical suture is used to close the edges of a wound or incision and to repair damaged tissue. The closure of wounds has a dramatic history, with some inventive methods. In ancient times, beetles or ants were used to close wounds. The living creatures were attached to the edges of the wound, which they clamped shut with their pincers. The insect body was then cut off, leaving the jaws in place. Army ants can be used for this purpose, due to their impressive pincers

We have made some advances since that time, and here is a nice summary:

Sutures are made from both man-made and natural materials. Natural suture materials include silk, linen, and catgut, which is actually the dried and treated intestine of a cow or sheep. Synthetic sutures are made from a variety of textiles such as nylon or polyester, formulated specifically for surgical use. A suture can also be classified according to its diameter. In the United States, suture diameter is represented on a scale descending from 10 to 1, and then descending again from 1-0 to 12-0. A number 9 suture is 0.0012 in (0.03 mm) in diameter, while the smallest, number 12-0, is smaller in diameter than a human hair.

64 year-old woman with a history of a humeral fracture, who presents with an arm mass. Oblique sagittal T1-weighted image reveals a 7 mm subcutaneous mass (red arrow), along with extensive metal artifact (yellow arrows):

The presence of extensive metal artifact made fat suppression difficult, and an ultrasound was performed to determine if the mass was solid or cystic:

The ultrasound confirmed the existence the mass, depicting an oval mass (red arrows) with irregular margins and no posterior acoustic enhancement. The mass was thus confirmed to be solid. In addition, within the posterior aspect of the mass, there was a linear, hyperechoic focus (yellow arrow), not conforming to a tissue plane.

Pathologic analysis revealed a suture granuloma. Suture granulomas can mimic neoplasms, especially at imaging. They are most commonly reported in the setting of inguinal herniorrhaphy, but can occur in other post-surgical settings as well. They can present as enhancing masses on MRI or CT, and can be associated with increased uptake at F-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET)/CT imaging (Kim et al., Kor J Rad 2009; 10:313-318). Suture granulomas have been reported to mimic recurrent thyroid carcinoma on ultrasound (Chung et al., Yonsei Med J. 2006; 47:748-751) and urachal tumor on CT (Gan and Wastie, J HK Col Radiol 2007; 10:59-61).

A recent report assessed the ultrasound features of suture granulomas at the thyroid bed after thyroidectomy for papillary thyroid carcinoma with an emphasis on their differentiation from locally recurrent thyroid carcinomas. Shape, heterogeneity, and the presence of central or paracentral internal echogenic foci (as in this case) were helpful criteria for differentiating suture granulomas from locally recurrent tumors in the thyroid bed.(Kim et al., Ultrasound in Med Biol 2009; 35,1452-1457). Thus, if you suspect that a mass may be a suture granuloma on MRI, a follow-up ultrasound may identify linear hyperechoic suture material within the lesion, and help suggest the diagnosis of a suture granuloma.

Vic David MD