The location and functional characteristics of the lesion were assessed from cine SSFP images covering the entire structure with gapless slices in 4-chamber and short-axis orientations as well as in 3-chamber view (Figure 2 and movie in Additional files 1 and 2). A smooth shaped mass, adhering to the posterior papillary muscle and posterior mitral valve leaflet, which was thickened and restricted in mobility, presented in the left-ventricular cavity, inducing mitral valve regurgitation. Enclosed within a hypointense layer, it appeared hyperintense to myocardium and isointense to blood. Foci of pulsatile signals were observed in the mass, suggesting vascularization. The volume of the lesion, evaluated by manual segmentation in 4-chamber view (Argus, Siemens AG, Healthcare Sector, Erlangen, Germany), however, did not show dependence on cardiac phase (8.6 ml in systole versus 8.4 ml in diastole).

For standard tissue characterization, dark-blood-prepared T1- and T2-weighted TSE images were acquired in end-diastole. The mass was isointense to myocardium on T1-weighted images (Figure 3A) and hyperintense to myocardium on T2-weighted images (Figure 3B,C). On both, T1-weighted and T2-weighted images, the mass contained hypointense regions indicating either patchy calcification or vascularization.

Gadolinium was injected at rest as a bolus (Gd-DO3A-butrol, 0.15 mmol per kg body weight followed by 30 ml saline flush, both infused at 3 ml/s). First-pass saturation recovery gradient-echo perfusion images were acquired in three 4-chamber, four short-axis and three 3-chamber slices covering the mass. There were no signs of myocardial infiltration (Figure 4A-C). Semi-quantitative tissue analysis was performed by manually segmenting the lesion in 4-chamber orientation; the results showed low contrast uptake in the lesion (Figure 4D).

Post-contrast cine FLASH (fast low-angle shot) imaging performed in 3-chamber, 4-chamber and short-axis orientations revealed the structure as a hypointense mass with foci of pulsatile signals (movie in Additional file 3), confirming findings of vascularization and no infiltration. Imaging of late gadolinium enhancement, acquired by inversion recovery gradient-echo sequences 10 minutes after contrast agent injection, demonstrated a thin, circumferential rim of contrast enhancement around the core of the mass and massive enhancement of the surface in multiple imaging planes (Figure 5).

When all aspects of soft-tissue signal and dynamic characteristics were considered together, the lesion could not be assigned to any of the suspected diagnoses: The morphological findings ruled out caseous calcification of the mitral valve [13] as well as valvular calcified thrombus [5], first-pass gadolinium uptake was inconsistent with the diagnosis of an intra-cardiac cyst [5, 14], and the lack of pronounced late gadolinium enhancement excluded the diagnoses of myxoma and papillary fibroelastoma [5, 15]. Overall, the findings mainly supported the diagnosis of a calcified intra-cardiac cyst of the mitral valve, because first pass contrast uptake was small and might have been neglected in cases of intra-cardiac cysts reported in literature (Table 1). To further analyse the content and the observed contrast agent uptake of the lesion, pre-contrast T1 and T2 and post-contrast T1 relaxation times were evaluated from single-breath-hold modified Look-Locker inversion recovery (MOLLI) [6, 7] and T2 preparation-based T2 mapping [8, 9] sequences by manually segmenting the lesion (Figure 6). Mean pre-contrast T1 and T2 times of the lesion of 2220 ± 144 ms and 151 ± 17 ms, respectively. These values were larger than pre-contrast myocardial magnetic relaxation times (T1 = 1144 ± 56 ms, T2 = 46 ± 4 ms), in particular explaining the qualitative pre-contrast signal intensity characteristics of the mass on T1- and T2-weighted TSE as well as SSFP images [16]. Since the T1 time of blood derived from the left ventricular cavity with 1654 ± 47 ms was substantially below T1 of the intra-cardiac lesion, the diagnosis of a blood cyst could be excluded as older blood typically should have shorter T1 times [17]. The decrease of T1 time of the lesion after contrast agent application to 925 ± 37 ms, however, affirmed the observed low contrast agent uptake in first pass perfusion and late enhancement imaging, and so the vascularization of the mass.

During surgery a smooth-shaped, white-yellowish mass was found on the ventricular side attached to the mitral valve and the posterior left ventricular wall (Figure 7A). The structure contained a cloudy fluid and presented with a villous inner wall consisting of cobblestone-shaped structures (Figure 7B). The mass was successfully resected and the mitral valve replaced (St. Jude). The postoperative course was uneventful.

Histologic evaluation revealed a calcified pseudocystic mass of the mitral valve. Surrounded by a fibrous, calcified envelope, the wall of the lesion contained a dense layer of connective tissue with multiple occluded vessels and calcifications, without an inner epithelial layer (Figure 7C) and with signs of a chronic inflammatory process indicating chronic endocarditis (Figure 7D). Malignancy was ruled out.

Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.