Lymphoepithelioma-like hepatocellular carcinoma: a case report with emphasis on the cytological features

Abstract

Lymphoepithelioma-like hepatocellular carcinoma (LEL-HCC) is a rare distinct histopathological subtype of HCC, which is characterized histopathologically by the presence of abundant lymphocytes around the neoplastic cells, and less than 50 cases have been reported. In this report, we describe the first cytological case of LEL-HCC. A 58-year-old Japanese male had an elevated serum alpha-fetoprotein (AFP) level, and computed tomography scan demonstrated a tumorous lesion with contrast enhancement in the liver, thus, surgical resection was performed. The Papanicolaou smear of the liver tumor demonstrated small clusters and trabeculae of large-sized polygonal cells in a background of an abundance of small lymphocytes. These tumor cells had a rich granular cytoplasm and large centrally located round to oval nuclei containing conspicuous nucleoli. Immunocytochemical analyses revealed that these cells were positive for AFP, glypican-3, and Hep-Par1. Histopathological study demonstrated LEL-HCC. The cytological features of the present case represent both lymphoepithelioma-like carcinoma and conventional HCC. The prognosis of LEL-HCC may be favorable. Therefore, the diagnosis of this type of tumor is important, and a cytological examination can provide useful information for diagnosis of LEL-HCC.

Introduction

Lymphoepithelioma-like carcinoma (LEC), which was originally described in the nasopharynx, is characterized histopathologically by undifferentiated carcinoma cells intermingled with abundant tumor-infiltrating lymphocyte. This type of rare carcinoma has also been reported in various organs, including lung, stomach, and bile duct [1-3]. Albeit extremely rare, lymphoepithelioma-like hepatocellular carcinoma (LEL-HCC) has been documented [4-8].

The cytological features of LEC of the skin, urinary bladder, uterine cervix, breast, and lung have been reported [9-16]; however, those of LEL-HCC have not been documented. In this report, we describe the first cytological case of LEL-HCC.

Case report

A 58-year-old Japanese male had an elevated serum alpha-fetoprotein (AFP) level (6,852 ng/mL; range <10) in a regular medical check-up. Laboratory tests revealed that his serum HBs antigen and HCV antibody were negative, and his PIVKA-II level was also elevated (240 AU/mL; range <40). A computed tomography scan demonstrated a well-circumscribed tumorous lesion, measuring 40 mm in diameter, with contrast enhancement in S6 of the liver. Therefore, surgical resection of the liver tumor with cholecystectomy was performed under a clinical diagnosis of HCC.

The post-operative course was uneventful, and no tumor recurrence has been observed during 2 months of medical follow-up.

The touch smear of the liver tumor was stained with Papanicolaou stain. Formalin-fixed and paraffin-embedded specimens of the resected liver tumor were processed for routine histological examination and immunohistochemical and in situ hybridization analyses.

In this report, immunohistochemical and in situ hybridization analyses were performed using an autostainer (Link48, DAKO Cytomation, Glostrup, Denmark). The primary antibodies used in this report were a rabbit polyclonal antibody against AFP (DAKO), a rabbit polyclonal antibody against CD3 (DAKO), a mouse monoclonal antibody against CD4 (4B12, DAKO), and a mouse monoclonal antibody against CD8 (C8/144B, DAKO), a mouse monoclonal antibody against CD20 (L26, DAKO), a mouse monoclonal antibody against glypican-3 (1G12, Nichirei Bioscience, Tokyo, Japan), and a mouse monoclonal antibody against Hep-Par1 (OCH1E5, DAKO).

This study was conducted in accordance with the Declaration of Helsinki, and the patient gave his informed consent.

Cytological findings

The Papanicolaou smear revealed small clusters and trabeculae of large-sized polygonal cells in a background of an abundance of small lymphocytes (Figure 1A, 1B). These cells had a rich granular cytoplasm and centrally located large round to oval nuclei containing vesicular chromatin and conspicuous nucleoli (Figure 1A, 1B).

Figure 1.

Cytological findings of the liver tumor. A. Small clusters of large polygonal cells in a background of many small lymphocytes, Papanicolaou stain, ×400. B. These polygonal cells have a rich granular cytoplasm and centrally located large round to oval nuclei containing conspicuous nucleoli, Papanicolaou stain, ×400.

Immunocytochemical findings

The polygonal cells were positive for AFP, glypican-3, and Hep-Par1 (Figure 2).

Figure 2.

Immunocytochemical findings of the liver tumor. Hep-Par1 (A), glypican-3 (B), and alpha-fetoprotein (C) are expressed in the tumor cells, ×400.

Histopathological findings

The tumor was relatively well-circumscribed and surrounded by a fibrous capsule. The neoplastic cells showed a thick trabecular growth pattern (Figure 3A), and had a rich eosinophilic granular cytoplasm and centrally located large round to oval nuclei and conspicuous nucleoli (Figure 3A, 3B). No pseudoglandular pattern was noted. The peculiar finding of this tumor was the presence of abundant infiltration of small lymphocytes around the tumor cells (>100 in ten high-power fields) (Figure 3A, 3B).

Figure 3.

Histopathological features of the liver tumor. A. Thick trabecular growth of neoplastic cells intermixed with abundant lymphocytic infiltration, HE, ×100. B. The tumor cells have a rich eosinophilic granular cytoplasm and centrally located large round to oval nuclei with conspicuous nucleoli, HE, ×400.

The liver tissue around the tumor showed no evidence of chronic hepatitis, although mild steatosis was noted.

Immunohistochemical and in situ hybridization findings

The majority of small lymphocytes were positive for CD3, and the number of CD4-positive lymphocytes was slightly larger than that of CD8-positive lymphocytes (Figure 4A-C). There were few CD20-positive lymphocytes. The neoplastic cells were positive for AFP, glypican-3, and Hep-Par1 (Figure 4D).

Figure 4.

Immunohistochemical features of the liver tumor. (A) Abundant CD3-positive lymphocytes are present around the tumor cells (×100). CD4-positive cells (B) are slightly more predominant than CD8-positive cells (C), ×100. (D) The neoplastic cells are positive for alpha-fetoprotein, ×100.

No EBER-positive tumor cells were noted.

According to these results, an ultimate diagnosis of LEL-HCC was made.

Discussion

LEL-HCC is a rare distinct histopathological subtype of HCC, and less than 50 cases have been reported in the English language literature [4-8]. Most of them were single case reports, however, recently the largest case series of this type of tumor has been published [4]. Chan et al. analyzed 20 surgically resected cases of LEL-HCC. The incidence was 4.9% of all HCC cases, and patients with LEL-HCC had a relatively lower frequency of males and frequently presented as a solitary tumor compared to patients with conventional HCC [4]. However, there were no significant differences in underlying chronic viral hepatitis, cirrhotic background, and serum AFP level [4]. Most of the tumor infiltrating lymphocytes were T lymphocytes, and the majority of them were CD8⁺ [4]. The vast majority of cases were not associated with EBER, unlike LEL cholangiocarcinoma. Clinically, LEL-HCC was associated with better overall and progression-free survival compared to conventional HCC [4].

In this report, we described the first cytological case of LEL-HCC. The common cytological features of LEC are as follows; i) the neoplastic cells are present singly as well as in cohesive clusters with admixture of inflammatory cells, such as lymphocytes and histiocytes, and ii) the neoplastic cells are large with high nuclear/cytoplasmic ratios, vesicular chromatin, and prominent nucleoli [10,13]. The typical cytological features of conventional HCC are as follows; i) the presence of neoplastic cells in broad trabeculae or cell groups lined with endothelial cells, ii) the neoplastic cells are polygonal, and have granular or vacuolated cytoplasm and centrally located large nuclei with conspicuous nucleoli, and iii) intracytoplasmic bile and bile plugs between neoplastic cells may be found [17]. Although intracytoplasmic bile and bile plugs were not observed in the present case, the above-mentioned cytological features of i) and ii) of HCC were noted. The present case clearly demonstrated that many small lymphocytes were admixed with the neoplastic cells, which is the characteristic feature of LEC. Thus, the present case represents the cytological features of both LEC and conventional HCC. According to these cytological features, a cytodiagnosis of LEL-HCC can be possible.

Immunocytochemical analyses may be useful for cytodiagnosis of HCC. In the present case, positive immunocytostaining for AFP and glypican-3 suggested that the neoplastic cells were neoplastic hepatocytes. Moreover, Hep-Par1 is also considered to be a useful marker of normal and neoplastic hepatocytes [17].

Regenerative nodules due to liver cirrhosis must be included in the differential diagnostic consideration of LEL-HCC because liver cirrhosis contains lymphocytes around the regenerative nodules. The most characteristic cytological features of the hyperplastic hepatocytes of the regenerative nodules are their polymorphism of the hepatocytes, which shows variation in cell size and shape, and the low nuclear/cytoplasmic ratio [18]. These features aid the differential diagnosis of LEL-HCC from regenerative nodules.

In conclusion, we report the first cytological case of LEL-HCC. The characteristic cytological feature of this rare tumor is the presence of abundant small lymphocytes around the neoplastic polygonal cells containing rich granular cytoplasm and large round to oval nuclei with conspicuous nucleoli. The prognosis of LEL-HCC may be favorable. Therefore, diagnosis of this type of tumor is important, and a cytological examination can provide useful information for diagnosis of LEL-HCC.

Disclosure of conflict of interest

None.