LAUSR

To review the clinical and imaging findings of patients with remote history of intramuscular (IM) in vitro fertilization (IVF) gluteal injections, presenting with signs and symptoms of a possible gluteal soft tissue sarcoma. Retrospective review of consecutive patients with a history of prior IVF therapy referred for MRI evaluation of a gluteal soft tissue mass was performed. Six patients were reviewed, with 5 patients meeting study inclusion criteria. Imaging exams (ultrasound n = 3, MRI n = 5) were assessed for lesion location, morphology, and intrinsic imaging characteristics. One case proceeded to percutaneous biopsy with histopathologic correlation. Average patient age was 43 years (range 38–50). Mean time interval between IVF IM injections and MRI was 5.7 years (range 2.2–13 years). Clinical findings included palpable gluteal mass (5/5) and local pain (4/5). Ultrasound showed heterogeneous subcutaneous lesions with varying complex cystic/solid internal echogenicity. On MRI, each case illustrated an irregularly marginated lesion, mean maximal dimension 3.5 cm (range 1.5–5.9 cm), within the deep gluteal subcutaneous fat composed of solitary (1/5) or multifocal (4/5) lobules demonstrating internal areas of high T1 and homogeneous low T2 fat suppressed signal with surrounding peripheral reticular high T2 signal. Correlative histological assessment showed central areas with features of fat necrosis and a peripheral inflammatory rim. In the setting of prior IVF therapy, imaging features of an irregularly marginated, deep subcutaneous gluteal lesion with inflammatory soft tissue changes surrounding solitary or multifocal areas of loculated fat signal may be seen as an inflammatory response to previous inadvertent subcutaneous injection(s).