PMC9636006_01
(A) Axial contrast-enhanced CT of the pelvis demonstrates a circumscribed soft tissue mass originating from the left spermatic cord with calcifications (black arrow) and small foci of fat (white arrow), typical of an immature germ cell tumor. (B) Transabdominal ultrasound with color Doppler shows a heterogeneously echogenic mass (arrow) with small cystic spaces, and no detectable blood flow.
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The abdominal CT revealed a 10 cm pelvic mass that was contiguous with tissue extending into the left inguinal canal, and predominantly composed of soft tissue with small foci of macroscopic fat and calcification (Fig. 1A). Pelvic ultrasound showed a heterogeneous mass without significant blood flow (Fig. 1B).
(A) Axial PET-CT shows increased metabolic activity involving the left cingulate gyrus (arrow) associated with a region of inflammation. (B) Axial FLAIR MR shows increased T2 signal of the left cingulate gyrus corresponding to the PET abnormality (arrow). (C/D) Axial DWI/ADC MR shows diffusion restriction in the left cingulate gyrus (arrow).
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PET/CT demonstrated increased radiotracer uptake in the pericallosal region of the brain, corresponding to findings of cingulate gyrus swelling with increased T2 signal and diffusion restriction on MRI, compatible with inflammation (Fig. 2). PET also demonstrated decreased uptake within bilateral occipital lobes, a classic finding in NMDA receptor encephalitis (Fig. 3).
FDG-PET statistical mapping analysis compares uptake throughout the brain relative to an age-matched cohort. (A) Fig 3A demonstrates a relative decrease in FDG uptake within the occipital lobe. (B) Fig 3B demonstrates a relative increase in FDG uptake within the cingulate cortex and anterior temporal lobes.
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PET/CT demonstrated increased radiotracer uptake in the pericallosal region of the brain, corresponding to findings of cingulate gyrus swelling with increased T2 signal and diffusion restriction on MRI, compatible with inflammation (Fig. 2). PET also demonstrated decreased uptake within bilateral occipital lobes, a classic finding in NMDA receptor encephalitis (Fig. 3).
(A) Coronal contrast-enhanced CT shows interval enlargement and heterogeneity of the pelvic mass with adjacent heterogeneous peritoneal blood products (arrow), consistent with mass rupture. (B) Coronal contrast-enhanced CT demonstrates hemoperitoneum in the upper abdomen (arrows). (C) Axial multiplanar reformat of the previously performed contrast-enhanced CT shows twisting of the mass pedicle from the left spermatic cord (arrow). (D) Coronal multiplanar reformat of the previously performed contrast-enhanced CT shows twisting of the mass pedicle from the left spermatic cord (arrow).
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Further scrutiny of the initial CT images in 3-D processing software demonstrated a twisted vascular pedicle, compatible with torsion as the cause of tumor rupture (Fig. 4).
(A) Gross images display a partially disrupted ovoid mass with attached spermatic cord. (B) When bivalved, the mass reveals a red-brown diffusely hemorrhagic cut surface with solid and cystic components and testicular remnant. (C) Histology sections reveal features of a mature teratoma, including cartilage (right), spindled mesenchymal cells (center) and neuroectodermal (left) cells. (D) There are features of seminoma including nests of large cells with clear cytoplasm and prominent nucleoli, separated by delicate fibrous septae, with admixed lymphocytes in the background (left).
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The mass was surgically resected later that day, with final pathology demonstrating a mixed GCT with adjacent testicular tissue (70% mature teratoma, 30% seminoma) (Fig. 5).
Multiple soft tissue nodules and masses are present in the abdomen and pelvis including adjacent to the sigmoid colon (A) and the cecum (B). These soft tissue nodules demonstrate internal calcification.
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Follow-up CT abdomen/pelvis 5 months later revealed increased size of these lesions despite normalization of tumor markers after chemotherapy (Fig. 6).