Teaching Case

A 40-year-old woman presented with a palpable lump in her left superior breast. Mammography and US and biopsy performed, confirming invasive carcinoma NST Grade 2. MRI performed pre-operatively due to occult on mammography.  Subsequent left breast mastectomy and reconstruction with right breast mastopexy.

MRI follow-up agreed as original cancer mammographically occult. MRI at 6 months and 18 months post-op.

Mammography – dense breasts with no abnormality demonstrated

US – Large irregular mass, measuring at least 4cm, in keeping with malignancy

MRI pre-op – Large avidly enhancing mass in the superior left breast in keeping with the biopsy-proven malignancy with adjacent satellite foci. Right breast appears normal.

MRI 6 months – small irregular mass in the posterior aspect of the right breast on the pectoral muscle. Left reconstructed breast appears normal.

MRI 18 months – interval increase in size of the right breast mass, which demonstrates enhancement but signal dropout in the centre of the lesion which is high on T2W imaging, in keeping with a stitch/suture granuloma

Final pathology on US-guided core biopsy – ‘fragments of inflamed granulation tissue associated with refractile suture material, in keeping with a suture granuloma’.

Background

Suture granulomas are localized inflammatory reactions in response to retained suture material. Silicone granulomas are the most common reported foreign body in the breast, but suture material, gauze sponge and clips from stereotactic biopsy have also been reported

Imaging Perspective

Suture granulomas are easily confused with recurrent malignancy after surgery and should be considered in the differential. MRI may show enhancement for up to 18 months. Biopsy under US or MRI guidance may be required if the imaging findings are in doubt to exclude malignancy.

Take Home Message / Teaching Points

Suture granulomas can be easily mistaken for recurrent malignancy. Careful interpretation of imaging findings with MRI can be useful in making the diagnosis, but enhancement can persist for many months after surgery.