With the recent U.S. Food and Drug Administration (FDA)-approval and rollout of the Pfizer-BioNTech and Moderna COVID-19 vaccines, it is important for radiologists to consider recent COVID-19 vaccination history as a possible differential diagnosis for patients with unilateral axillary adenopathy. Hyperplastic axillary nodes can be seen on sonography after any vaccination but are more common after a vaccine that evokes a strong immune response, such as the COVID-19 vaccine. As the differential of unilateral axillary adenopathy includes breast malignancy, it is crucial to both thoroughly evaluate the breast for primary malignancy and to elicit history of recent vaccination. As COVID-19 vaccines will soon be available to a larger patient population, radiologists should be familiar with the imaging features of COVID-19 vaccine induced hyperplastic adenopathy and its inclusion in a differential for unilateral axillary adenopathy. Short-term follow-up for unilateral axillary adenopathy in the setting of recent COVID-19 vaccination is an appropriate recommendation, in lieu of immediately performing potentially unnecessary and costly axillary lymph node biopsies.

Uterine MMMT most commonly presents as an intracavitary mass with coexistent dilatation of the endometrial canal. Tumors tend to appear hyperechoic on sonography, heterogeneously hypodense and ill defined on contrast-enhanced CT, and heterogeneously hyperintense on T2-weighted MR images with signal abnormalities indicating subacute hemorrhage on T1-weighted MR images. Myometrial invasion is common and has a predilection for the uterine fundus.

With the increasing popularity of assisted reproductive technology (ART), radiologists are more likely to encounter associated complications, especially in an emergency setting. These complications include ovarian hyperstimulation syndrome (OHSS), ovarian torsion, and ectopic and heterotopic pregnancy. OHSS occurs following ovulation induction or ovarian stimulation and manifests with bilateral ovarian enlargement by multiple cysts, third-spacing of fluids, and clinical findings ranging from gastrointestinal discomfort to life-threatening renal failure and coagulopathy. Enlarged hyperstimulated ovaries are at risk for torsion. Clinical symptoms are often nonspecific, and ovarian torsion should be suspected and excluded in any female patient undergoing infertility treatment who presents with severe abdominal pain. The most consistent imaging finding is asymmetric enlargement of the twisted ovary. There is also an increased risk for ectopic pregnancy following ART, with a relative increased risk for rarer and more lethal forms, including interstitial and cervical ectopic pregnancies. Heterotopic pregnancy refers to simultaneous intrauterine and ectopic pregnancies and has an incidence of 1%-3% in ART patients. Careful evaluation of the adnexa is critical in this patient population, even when an intrauterine pregnancy has been confirmed. Ultrasonography is the first-line imaging modality for the evaluation of complications of ART, although nonspecific symptoms may sometimes lead to cross-sectional imaging being performed. Familiarity with the multimodality imaging appearance of these entities will allow accurate and timely diagnosis and help avert potentially fatal consequences.