Renal carcinoma with “omental cake” peritoneal metastatization at diagnosis

Clinical History

Man with unremarkable past medical history, referred to undergo abdomino-pelvic multidetector CT (MDCT) because of increasing lower abdominal pain over three weeks without associated symptoms, under clinical suspicion of diverticulitis.
Laboratory tests (including renal function and urinalysis) within normal limits, apart from raised (56 mg/L) C-Reactive Protein.

Imaging Findings

Multidetector CT (Fig. 1) detected a 4x3 cm solid, enhancing central left kidney mass contained within the renal parenchyma, consistent with Robson stage I, TNM T1 stage renal carcinoma. Additionally, moderate diffuse thickening of the pelvic peritoneal serosa was noted, associated with confluent soft-tissue densities in the greater omentum suggesting an “omental cake”. Ascites, lymphadenopathies, venous thrombi, and liver, lungs, or skeletal metastases were excluded.
Due to this appearance exceptionally associated with renal cancer, search for a coexisting primary tumour causing peritoneal metastatization (including upper and lower digestive endoscopy), urinary cytology, and tuberculosis serology were performed with negative results.
Explorative surgery confirmed extensive peritoneal carcinomatosis with omental caking. Peritoneal lavage cytology, biopsy samples from omentum and renal mass confirmed clear cell carcinoma with peritoneal metastatization, resulting in M1, stage IV reclassification.
Nephrectomy was postponed after chemotherapy; however, disease progression with appearance of ascites was observed at MDCT follow-up (Fig. 2).

Discussion

Renal cell carcinoma (RCC) represents the majority of primary kidney malignancies, and accounts for 2-4% of all adult cancers. With widespread use of diagnostic imaging, currently about half RCCs are incidentally detected, often at an early stage amenable to nephron-sparing surgery, alternatively to interventional therapies such as radiofrequency- or cryoablation [1-3].
RCC predominantly spreads by direct extension, lymphatic dissemination, and venous invasion. Prognosis depends on pretreatment staging, and on histologic subtype, with chromophobe and papillary less aggressive than usual clear-cell RCCs. Whereas 5-year survival approaches 60-90% for tumours confined within renal capsule, prognosis is dismal with lymphatic and hematogenous metastatization. The lungs, bones, liver and brain are involved in descending order of frequency [2-4].
Metastatization to peritoneum and omentum at diagnosis is exceptionally reported in few case reports, and occurs via haematogenous dissemination or direct invasion through renal capsule and anterior renal fascia to the posterior parietal peritoneum. Peritoneal carcinomatosis (PC) is also extremely rare as neoplastic progression or recurrence, and identified at autopsy in only 1% of patients [5-8].
High-resolution multiphasic multidetector CT (MDCT) is the preferred modality to detect, characterize, and stage RCC according to the traditional Robson and TNM systems, including tumour size, invasion of perinephric fat, adrenal gland or adjacent organs, lymphadenopathies, neoplastic venous invasion, and distant metastases. Renal masses are precisely localized preoperatively including relationship to kidney surface, collecting system, arterial and venous vessels [1-2, 9].
Sometimes asymptomatic, PC is diagnosed synchronously with primary tumour in 55% of cases, whereas advanced stages cause abdominal enlargement, pain and vomiting. Most PC occurrences are secondary to ovarian, gastrointestinal tract, gallbladder, pancreatic, or breast cancers. PC may result from direct extension of the primary tumour, intraperitoneal seeding, lymphatic or haematogenous spread, represents disseminated disease and is generally associated with poor prognosis [8, 10-11].
At MDCT, PC shows serosal thickening, peritoneal nodules, plaques or soft-tissue sheets. Early stages are appreciated as fat stranding and “smudged” infiltration in the greater omentum. Lesions progress or coalesce to form an “omental cake” or discrete masses. Variable amounts of ascites are usually associated [8, 10-11].
The exceptional possibility of PC from primary RCC should be considered when characteristic imaging findings are observed: this feature dramatically changes stage and prognosis. In this case, differential diagnosis mostly includes PC from another primary cancer, and peritoneal tuberculosis [8, 11].
Although surgery remains the treatment of choice, innovative systemic targeted therapies such as imatinib are being evaluated for disseminated RCC [9].

Differential Diagnosis List

Final Diagnosis

Peritoneal metastatization with omental caking from contained clear-cell renal carcinoma

URL:	https://www.eurorad.org/case/10654
DOI:	10.1594/EURORAD/CASE.10654
ISSN:	1563-4086