Hepatic Lymphoma

Etiology

Certain viruses such as hepatotropic and non-hepatotropic viruses share links with the causation of the PHL. Of note, the common hepatotropic viruses linked with the causation of PHL are hepatitis C virus (HCV) and hepatitis B virus (HBV) infections.[6][7][8][9] Some uncommon non-hepatotrophic viruses such as HIV, HEV, and Cytomegalovirus (CMV) also have been reported in the literature. Certain autoimmune diseases, namely systemic lupus erythematosus (SLE), may also have links with PHL.[10]

In a large case series of over 69 patients with PHL, the prevalence of seropositive HBV infections was 20%; however, the majority of the patient population was from the western world.[11] In contrast to this, one author reported only 4% of cases of PHL harboring HBV infection out of 90 individuals. The majority of the patient population was of Asian origin, which was then considered an endemic region of HBV infection.[12] Another study from China showed positive HBV surface antigen among 21/35 (60%) of Chinese patients.[13] However, considering the high prevalence of HBsAg positivity of around 10% among the Chinese population suggests that the association of HBV with PHL may be coincidental rather than directly involved in the causation of PHL. A common hepatotrophic virus such as HCV was positive among 6 of 28 (21%) immune-competent PHL patients. Most of these HCV-infected patients have had a high-grade B-cell lymphoma.[6]

Epidemiology

Considering the rarity of primary hepatic lymphoma, its exact incidence remains undetermined. However, in the literature, it is reported to be 0.4% of all cases of extranodal non-Hodgkin lymphoma and 0.016% of all cases of non-Hodgkin lymphoma.[14] The mean age of occurrence of PHL is 50 years; males are more prone to develop PHL in comparison to females (1.7 to 1.0). 

Pathophysiology

Despite well-established underlying pathophysiology in the pathogenesis of other forms of lymphoma, both non-Hodgkin and Hodgkin lymphoma, the pathophysiology underlying primary hepatic lymphoma is largely underdetermined. An exception to this is the association of primary hepatic lymphoma with some viruses, notably the hepatitis C virus (HCV), where the virus is thought to stimulate B cells which initially leads to polyclonal and then to monoclonal B cell expression. Hepatitis C virus has been proposed to cause translocation and hence overexpression of the anti-apoptotic factors, bcl2, and monoclonal IgH rearrangement. Additionally, HCV alters the transcriptional regulation of genes like p21, p53, and H-ras by the viral core and/ or NS35 proteins.[9] Similarly, hepatitis B virus infection is thought to produce B cell antigenic stimulation resulting in monoclonal B cell proliferation.[9]

Histopathology

Despite all non-invasive methods to detect liver lymphoma, histopathological examination is required to confirm the diagnosis. Histopathologically, primary hepatic lymphoma can be of various types, including non-Hodgkin lymphoma, diffuse large B-cell lymphoma (DLBCL) or T cell lymphoma, and in some instances non-B non-T cell lymphoma. Diffuse large B-cell lymphoma is the most prevalent compared to other variants of non-Hodgkin lymphoma.[12]

In one case series of over 41 patients, 34 (83%) of patients had B cell lymphoma, predominantly of diffuse large B-cell lymphoma (27/34) (79.41%). However, there were also rare reports of other cell types, such as T-cell lymphoma, precursor T-cell lymphoblastic lymphoma, and Burkitt lymphoma.[10] In a case series of 10 patients, eight patients had diffuse large B cell lymphoma, one had Burkitt lymphoma, and one had T cell type lymphoma.[15] In yet another case series, MALToma has been reported to be the second most common variant of lymphoma after diffuse large B-cell lymphoma, affecting 8/20 (40%) of patients with primary hepatic lymphoma.[7]

Histopathologic features of the commonly reported diffuse large B-cell lymphoma are the abundant mitotically active large and atypical cells in the wall of the mass with pale to clear cytoplasm and vague cell membranes associated with granular, eosinophilic necrotic debris. The nuclei are large with condensed or open chromatin with prominent nucleoli. On Immunohistochemical analysis, positive pan B markers such as CD 20, negative epithelial tumor markers, namely the cytokeratin AE1/AE3, positive pan T cell markers CD3 and Tdt, and the absence of Hep Par 1 coincides with the diagnosis of diffuse large B-cell lymphoma.

History and Physical

The majority of patients with primary hepatic lymphoma present with vague symptoms such as nausea, vomiting, upper abdominal discomfort, and jaundice.[2][3] Hepatomegaly may also be present and can range from moderate to severe, resulting in patient abdominal discomfort.[10][16][17] Like non-Hodgkin lymphoma, with few exceptions, notably the Burkitt lymphoma, the disease course is indolent among most patients with primary hepatic lymphoma. Many patients fail to realize that a subtle right-sided pain or lump is significant until the tumor size is sufficiently enlarged to disturb the liver capsule. Some rare presentations of primary hepatic lymphoma include acute liver failure and chronic hepatitis.[18] Congestive splenomegaly can also occur in primary hepatic lymphoma due to hepatic dysfunction and portal hypertension.

Evaluation

Following a history and comprehensive physical examination to rule out features of systemic lymphoma, including generalized superficial lymphadenopathy, evaluation is mostly dependent on excluding the common causes of space-occupying liver lesions, notably hepatocellular carcinoma, metastatic liver disease, hepatic adenoma, hemangioma, and hydatid cyst. A thorough workup is helpful, including HBsAg, HCV antibodies, EBV IgM or PCR, and HIV serology. A range of other biochemical and tumor markers such as serum LDH, B-2 microglobulin, alpha-fetoprotein (AFP), serum carcinoembryonic antigen (CEA), CA 19-9, and CA-125 are required to prognosticate the tumor and to differentiate between the primary vs. metastatic liver disease.

Imaging studies, such as triphasic CT scan of the liver, are helpful to define characteristics of the liver lesion and can also help to determine the underlying co-existent liver cirrhosis and associated organ involvement. In contrast to hepatocellular carcinoma, which shows arterial as well as portovenous and delayed phase enhancement, the lesion of lymphoma may only show arterial phase enhancement. The lesions are mostly hypodense with heterogeneous patterns, which is suggestive of tumor-related infarction and necrosis within the lesion.[19]

Radiologically, primary hepatic lymphoma can present in three forms:

• A solitary lesion (55 to 60%)
• Multiple lesions within the liver (35 to 40%)
• Diffuse hepatic infiltration

Treatment / Management

Since primary hepatic lymphoma is rare, the majority of evidence regarding treatment and tumor response comes from case series. Furthermore, the response to different strategies, i.e., surgery vs. chemotherapy, is again drawn from discrete case series.

One case series by Yang X.W. et al. demonstrated the prognosis of eight patients who have had surgical resection of the tumor.[20] They reported that out of eight patients, one patient did not survive due to the postoperative complication and died on the eighth postoperative day. The cumulative six months, 1-year, and 2-year survival rates were 77.8%, 66.7%, and 55.6%, respectively, with a median survival of 23 months. Only one patient remained alive and tumor-free after five years following tumor resection. Additionally, they also noted that postoperative chemotherapy was a significant prognostic factor for survival (P = 0.006).[20](B2)

In contrast to the above study, Page et al. determined that the combination chemotherapy helped achieve complete remission among 83.3% of patients and 5 years cause-specific and failure-free survival rates were 87.1% and 70.1%, respectively.[16] In addition to the above study, Peng Y et al. found 70% of their patients did respond to the combination chemotherapy.[15](B2)

Prognosis and treatment response further depends on the size of the tumor; notably, tumors of greater than 7 cm in size, serum lactate dehydrogenase levels over 10% of the upper limit of the normal, raised beta-2 microglobulin levels in excess of 3 mg/dl, and presence of constitutional symptoms.[16](B2)

Among patients with no high-risk factors, treatment with combination chemotherapy consisting of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) is usually effective in achieving remission. Among patients with the presence of at least one or more than one pre-treatment risk factors requires consideration of using altering triple combination. Alternate regimens consist of doxorubicin, methylprednisolone, cytosine arabinoside, and cisplatin, alternating with methotrexate, bleomycin, cyclophosphamide, doxorubicin, vincristine, and methylprednisolone.[16](B2)

Differential Diagnosis

The common differentials of primary hepatic lymphoma are the other space-occupying lesions of the liver:

• Hepatocellular carcinoma
• Metastatic liver disease
• Hepatic adenoma
• Hemangioma
• Liver abscess
• Hydatic cyst

However, in the majority of the cases, imaging followed by a targeted biopsy of the lesion helps to confirm the diagnosis.

Prognosis

Primary hepatic lymphoma is sensitive to combination chemotherapy, with complete remission can be achieved among more than 80% of the patients. The 5-year cause-specific survival approaches 87.1%.[16] Prognosis after surgical resection is highly variable, and the significant risk of postoperative bleeding due to the vascular nature of the tumor further increases the morbidity and mortality rates after surgical intervention.

Complications

Some patients with primary hepatic lymphoma can develop acute liver failure, which carries a significant risk of mortality. Tumor bleeding and hematological spread to other locoregional lymph nodes have also been documented.