Contrast-enhanced ultrasonography findings of LAMNs with peritoneal and splenic metastases: a case report and literature review

Abstract

Low-grade appendiceal mucinous neoplasms (LAMNs) are rare appendiceal tumors that are primarily diagnosed using computed tomography(CT) enhancement and magnetic resonance imaging (MRI). Herein, we report the sonographic features, especially for contrast-enhanced ultrasound (CEUS), of a 70-year-old female with an unusual LAMN metastasizing to the peritoneum and spleen. The patient had a right pelvic mass 2 days prior to presentation. Two-dimensional (2D) ultrasound revealed a mixed cystic-solid mass in the right lower abdomen and spleen parenchyma; CEUS showed heterogeneous enhancement in both areas, suspected to be a mucinous mass. CT enhancement and MRI findings revealed concurrent findings. Histopathologically, LAMN lesions were confirmed in the appendix, spleen, and peritoneum of the specimens obtained during exploratory laparoscopy. No recurrences were reported at three years postoperatively. LAMN lesions may metastasize to abdominal organs, and imaging examinations are essential for diagnosis. This study presents major ultrasonography and CEUS findings for the diagnosis of LAMNs.

Keywords: appendix; mucinous neoplasms; ovarian neoplasms; spleen; ultrasonography.

Figure 1

Two-dimensional Color Doppler images of the lesion in the right lower abdomen and spleen obtained by transabdominal ultrasound. (A) Longitudinal view of the transabdominal ultrasound scan of the right lower abdomen, showing a mixed cystic and solid echo. The solid part (asterisk) was eccentric, most of the surrounding tissue was cystic, and a radial stripe light band was seen in the dark area connected to the solid part. (B) Color Doppler of the mass showed minimal linear blood flow in the solid part; heterogeneous echogenicity was observed in the right adnexa, mainly anechoic around some hyperechoic echogenicity in the center. (C) Transabdominal ultrasound of the spleen showing a mixed cystic and solid mass (※) in the left hypochondrium, with irregular dark liquefied areas septate (left-right diameter of the mass: 7.52 cm). (D) Color Doppler image showing sparse blood flow in the solid part and no significant blood flow distribution in the cystic part.

Figure 2

CEUS shows a lesion in the right lower abdomen and spleen. (A) In the transabdominal contrast-enhanced ultrasound examination, the solid capsular part of the mass in the right lower abdomen began to perfuse at 11 s (yellow arrow). (B) Isoenhancement is seen in the center (yellow arrow), and no contrast perfusion is observed in the cystic portion. (C) During the transabdominal contrast-enhanced ultrasound examination, the mixed mass of cystic and solid capsulated in the spleen began to perfuse at 14 s (yellow arrow). The contrast agent was unevenly distributed, with visible perfusion in the solid part but not in the cystic part. (D) The contrast agent entered the solid part (yellow arrow), which was isoenhanced, and the enhancement subsided at 37 s, which was earlier than that of the normal spleen tissue.

Figure 3

Transvaginal ultrasound images of the uterus and bilateral adnexa of the patient. (A, C) Atrophic right and left ovaries can be visualized. (B) TVU image revealing an atrophic uterus without intimal thickening.

Figure 4

MRI and CT findings of the lesion in the right lower abdomen and spleen. (A, B) Axial view of the abdominal magnetic resonance scan revealed a slightly short T2 signal, a heterogeneous high signal in the diffusion-weighted image, and high signal intensity in the solid part (white arrow). (C) Axial view of contrast-enhanced computed tomography showing a multilocular cystic focus at the lateral splenic border (white arrow), which showed no significant enhancement after intracystic contrast perfusion, and intensity enhancement of the cyst wall after contrast perfusion. (D) Axial view of contrast-enhanced computed tomography revealed a mixed mass in the right lower abdomen, with significant enhancement in the central solid part.

Figure 5

Intraoperative view during exploratory laparoscopy and microscopic histopathological examination of lesions. Intraoperative view during exploratory laparoscopy revealed a yellow cystic mass in (A) the appendix region, with a milky white flocculent light band (red arrow) in the cyst. (B) Intraoperative view during exploratory laparoscopy revealing multiple yellow vesicular nodules (black arrow) in the peritoneum. (C) Hematoxylin and eosin (HE) staining of a low-grade mucinous tumor of the spleen, involving both the parenchyma and exterior of the splenic capsule and low-grade mucinous epithelial cells in the mucus lake. Original magnification: ×10.