Case Report
A 13-year-old female patient, who was previously healthy, applied with
the complaints of fatigue and fever. On her physical examination, there
was tenderness in the abdomen. The patient’s laboratory tests revealed
elevations of the liver enzyme tests (Grade1-2, CTCAE v5). In the
abdominal ultrasonography, omental thickening near the pelvic region,
soft tissue appearance and dense fluid related to the parametrial areas
were observed. Contrast-enhanced abdominal magnetic resonance imaging
revealed soft tissue with diffusion restriction and contrast enhancement
in the pelvic region, thickening of the peritoneal surface and omentum
around the liver, and enlargement of the pelvic lymph nodes. The
differential diagnosis included tuberculosis, peritoneal carcinomatosis,
and lymphoma-like involvement. Laparoscopy was performed to investigate
the etiology of fever of unknown origin and an abdominal mass. In the
laparoscopy procedure, lymph node excision and biopsy, appendectomy
(perforated appendicitis), omentectomy, peritoneal washing and
debridement were performed. The pathology result was epithelioid type
malignant mesothelioma. It was detected that the tumor infiltrated the
appendix serosa and wall, peritoneal tissue, omental tissue and lymph
nodes. Widespread positivity was detected with CK5, CK6, CK 7,
mesothelin and calretinin in tumor cells. Mild to moderate positivity
was observed with D2-40. Multifocal cytoplasmic positivity was detected
with epithelial membrane antigen. Other markers were found negative. To
determine the extent of the tumor, the first positron emission
tomography (PET/CT) was obtained. Except for the normal physiological
accumulation sites of the given radiopharmaceutical, diffuse
pathological activity accumulation (maximum standard uptake value,
SUVmax: 9.0) was observed on the peritoneal surface, prominently in the
pelvis and in the pericapsular area of the liver periphery (Figure 1a).