Hepatocellular carcinoma (HCC) disseminates via the lympho-vascular route to the lymph nodes or the distant organs in a majority of the cases in which metastasis occurs. Although peritoneal spread of HCC has been reported in the pathology literature on numerous occasions,[2–8] to date there has been only one large study performed, specifically analyzing this phenomenon.[4]

Specimens with non-negative results underwent further investigation. The original slides as well as any immunocytochemical studies performed for clinical purposes were reviewed. Immunocytochemistry was performed on a Dako Autostainer Universal Staining System (Dako North America, Carpinteria, CA). Follow-up patient history was also compiled. No additional studies were performed on archival materials for this study.

Alcohol abuse was the most common cause of cirrhosis in this patient population, accounting for 44 cases alone and 22 more in combination with hepatitis viruses. The hepatitis C virus alone accounted for 30 cases and Hepatitis B virus alone for six cases. Other causes included: non-alcoholic steatohepatitis (seven cases), autoimmune hepatitis (three cases), sarcoidosis (one case), cardiogenic cirrhosis (one case), and alpha-1-antitrypsin deficiency (one case). Cirrhosis was cryptogenic in the remaining 18 cases.

Among these cirrhotic patients, 17 had a history of HCC, either confirmed by biopsy or strongly suspected on the basis of radiological studies. Two others had a history of previously resected HCC. Only one patient had a history of metastatic HCC.

Additional confounding factors were present in some cases: The status of fifteen patients was post liver transplant with recurrent liver failure; seven were known to be positive for Human Immunodeficiency Virus, and eight had a history of non hepatic malignancy.

Of the 167 specimens, 162 were negative. Atypical lymphocytes were present in two of the patients. One of these patients had a known history of diffuse large B-cell lymphoma. Peritoneal involvement by a monoclonal B-cell process was confirmed in a concurrent ascites fluid specimen sent to the flow cytometry laboratory. The other patient had a history of severe combined immunodeficiency syndrome. Flow cytometry revealed no clonal population; however, a previous paracentesis sent to hematopathology, and a subsequent bone marrow specimen, were suspected to have T-cell lymphoproliferative disorder.

Three cases had atypical epithelioid cells identified. In all the three cases, the cells of interest were large, with a high nucleus-to-cytoplasm ratio and nuclear changes including moderate anisonucleosis and prominent nucleoli. A few mitoses were observed. The cells of interest were also predominantly dyscohesive in every case, although cohesive clusters were present in two cases. No distinct second cell population was present in any of the three cases. Nuclear contour irregularities and chromatin clumping ranged from minimal to marked, while multinucleation ranged from rare to frequent in the different specimens. Upon review, the atypical cells from all the three cases are believed to be reactive mesothelial cells. All three patients died within a few days of the collection of the ascites fluid specimens, with atypical epithelioid cells present. Autopsies were not performed on any of these cases.

Case #1 was a 58-year-old female with end-stage cirrhosis due to Hepatitis B infection. Abdominal computed tomography scans demonstrated a small, nodular liver with a large exophytic mass, suspicious for HCC. She had had a previous negative ascites fluid cytology during the study period. The atypical epithelioid cells were present only on the cell block [Figure 1]. The atypical epithelioid cells were negative by mucicarmine special stain and positive for calretinin [Figure 2] (Cell Marque, Rocklin, CA; dilution 1: 80), WT-1 (Dako, Carpineria, CA; dilution 1: 50), and cytokeratin 5/6 (Dako, Carpinteria, CA; dilution 1: 50) by immunocytochemistry, confirming a mesothelial origin. Acute inflammation was also present. The patient died from catheter-associated sepsis, soon after the specimen was collected.

Case #2 was a 65-year-old male, with a history of alcoholic cirrhosis complicated by hepatorenal syndrome requiring dialysis and a remote history of surgically resected renal cell carcinoma. A computed tomography scan performed at the time of the paracentesis demonstrated widespread metastatic disease, presumed to be renal cell carcinoma recurrence. As with case 1, this patient had had a previous negative ascites fluid cytology. Atypical epithelioid cells were seen in Papanicolaou stained smears [Figure 3] and in a cell block. He had the following immunocytochemical findings: cells of interest in the cell block stained positive for calretinin [Figure 4], WT-1, and cytokeratin 5/6 and negative for B72.3 (Covance/Signet, Dedham, MA; dilution 1: 60) and CD10 (Leica/Novocastra, Bannockburn, IL; dilution 1: 50) as well as a special stain for mucicarmine. The patient died shortly after paracentesis, with peritonitis as a probable contributing factor.

Case #3 was a 76-year-old female with a history of autoimmune hepatitis causing cirrhosis status-post liver transplant. Atypical epithelioid cells were seen in Papanicolaou stained smears [Figure 5]. The patient died from sepsis soon after the specimen was acquired, possibly arising from peritonitis. No additional studies were performed on the cytology specimen. Computed tomography scans just before the death of the patient did not show any conclusive evidence of tumor anywhere in the pelvis, abdomen, or thorax. A loculated perihepatic fluid collection was present, associated with peritoneal thickening, for which an infectious etiology was favored.

Many studies in the pathology literature acknowledge that, in general, involvement of the peritoneum by HCC is rare, with the reported cases presented as interesting exceptions.[5,6,8] Only one group has suggested that cytologic analysis of ascites fluid could lead to the diagnosis of HCC in a substantial number of cases.[3,4] These authors used a retrospective design, in which they analyzed prior cytology specimens from patients who later had HCC confirmed by autopsy. The authors do not state whether they had rendered a diagnosis of HCC at the time the ascites fluid specimens were interpreted for clinical purposes. In the more detailed of these studies, the authors report ascites fluid cytology specimens that were positive for HCC in 10 out of 106 patients (9.4%).[4] Based on this finding, they assert that ascites fluid analysis may have value for the initial investigation of possible HCC. However, these authors relied on analysis of archived slides reviewed in the light of later autopsy findings, a scenario quite different from routine clinical work. Furthermore, they used an immunocytochemical panel consisting of polyclonal carcinoembryonic antigen (pCEA), cytokeratins 8 and 18, and erythropoietin (ERY-1) to confirm the hepatic origin of the atypical cells they observed. With the exception of pCEA, which was negative in all the cases with material suitable for staining,[4] these antibodies would not be used in a contemporary panel. While this study has the merit of including a large number of patients with confirmed HCC, the design limits its applicability to practice.

Many of the individual reported cases of peritoneal carcinomatosis caused by HCC feature variants including clear-cell HCC,[8] sarcomatoid HCC,[5] fibrolamellar HCC[6] or anaplastic carcinoma thought to be derived from HCC.[6] This indicates that even when the HCC does involve the peritoneum, it tends to come from high-grade or unusual variants of HCC that may display atypical metastatic patterns, in accordance with their atypical overall biology.

We have demonstrated more conclusively than previous reports that positive cytology findings are very unusual in patients with cirrhosis with or without HCC. A vast majority of our specimens were negative, with only three identified cases that contained atypical epithelioid cells. Interestingly, all three came from terminally ill patients with evidence of acute peritonitis. Furthermore, two of the patients had previous negative findings in ascites fluid specimens taken when they were in better health. This indicates that even the rare atypical cases that may arise often represent reactive changes in severely ill patients. While we do not deny the possibility that HCC may cause peritoneal carcinomatosis, we believe this to be an extremely rare manifestation of the disease.

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Each author has participated sufficiently in the work and take public responsibility for appropriate portions of the content of this article.