EBV-associated anorectal lymphomas in patients with acquired immune deficiency syndrome

HIV-related Malignancies and Mimics: Imaging Findings and Management

The risk of developing malignancy is higher in patients with human immunodeficiency virus (HIV) infection than in non-HIV-infected patients. Several factors including immunosuppression, viral coinfection, and high-risk lifestyle choices lead to higher rates of cancer in the HIV-infected population. A subset of HIV-related malignancies are considered to be acquired immunodeficiency syndrome (AIDS)-defining malignancies, as their presence confirms the diagnosis of AIDS in an HIV-infected patient. The introduction of highly active antiretroviral therapy (HAART) has led to a significant drop in the rate of AIDS-defining malignancies, including Kaposi sarcoma, non-Hodgkin lymphoma, and invasive cervical carcinoma. However, non-AIDS-defining malignancies (eg, Hodgkin lymphoma, lung cancer, hepatocellular carcinoma, and head and neck cancers) now account for an increasing number of cancer cases diagnosed in HIV-infected patients. Although the number has decreased, AIDS-defining malignancies account for 15%-19% of all deaths in HIV-infected patients in the post-HAART era. Most HIV-related malignancies in HIV-infected patients manifest at an earlier age with a more aggressive course than that of non-HIV-related malignancies. Understanding common HIV-related malignancies and their specific imaging features is crucial for making an accurate and early diagnosis, which impacts management. Owing to the weakened immune system of HIV-infected patients, other entities such as various infections, particularly opportunistic infections, are prevalent in these patients. These processes can have confounding clinical and imaging manifestations that mimic malignancy. This article reviews the most common AIDS-defining and non-AIDS-defining malignancies, the role of imaging in their diagnosis, and the imaging mimics of malignancies in HIV-infected patients. ^©RSNA, 2018.

MYC Negative Rectal B-Cell Lymphoma, Unclassifiable, with Features Intermediate between Diffuse Large B-Cell Lymphoma and Burkitt's Lymphoma in an Immunocompetent Patient

B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt's lymphoma (BLUI) is a recently added entity to the World Health Organization (WHO) classification to address a grey zone between large B-cell lymphoma (DLBCL) and Burkitt's lymphoma (BL). These are rare aggressive lymphomas, which were previously also known as Burkitt's-like lymphoma (BLL). BL and BLUI/BLL of the colon mostly involve the ileocecal region. In the rectum, BL and BLUI/BLL almost always affect patients with the acquired immune deficiency syndrome (AIDS). We report the first case of rectal BLUI/BLL in an immunocompetent patient who is also negative for MYC abnormalities and the EBV early RNA (EBER) in situ hybridization.

Review of HIV-Related Cytopathology

Exfoliative and aspiration cytologies play a major role in the management of patients with human immunodeficiency virus infection. Common cytology samples include cervicovaginal and anal Papanicolaou tests, fine needle aspirations, respiratory specimens, body fluids, Tzanck preparations, and touch preparations from brain specimens. While the cytopathologists need to be aware of specific infections and neoplasms likely to be encountered in this setting, they should be aware of the current shift in the pattern of human immunodeficiency virus-related diseases, as human immunodeficiency virus patients are living longer with highly active antiretroviral therapy and suffering fewer opportunistic infections with better antimicrobial prophylaxis. There is a rise in nonhuman immunodeficiency virus-defining cancers (e.g., anal cancer, Hodgkin's lymphoma) and entities (e.g., gynecomastia) from drug-related side effects. Given that fine needle aspiration is a valuable, noninvasive, and cost-effective tool, it is frequently employed in the evaluation and diagnosis of human immunodeficiency virus-related diseases. Anal Papanicolaou tests are also increasing as a result of enhanced screening of human immunodeficiency virus-positive patients for cancer. This paper covers the broad spectrum of disease entities likely to be encountered with human immunodeficiency virus-related cytopathology.

Anorectal Epstein-Barr virus infection mimicking Hodgkin lymphoma in an immunocompetent man

Anorectal Hodgkin lymphoma (HL) is rare, mainly described in human immunodeficiency virus (HIV) patients with exceptional cases reported in immunocompetents. We report the case of a middle age HIV male, presenting with intestinal occlusion. Rectosigmoidoscopy showed multiple anorectal nodular and ulceronecrotic masses. The biopsy specimens revealed a diffuse polymorphous inflammatory infiltrate in the lamina propria, associated with CD30, CD20, CD3, CD15, and ALK1 scattered large Hodgkin and/or Reed Sternberg -like cells stained by LMP1 antibody and EBER. A diagnosis of EBV-associated atypical lymphoproliferative disease mimicking HL was made. These lesions remained stable for 2 years without treatment then disappeared leaving a mucosal scar. A later control biopsy showed a condylomatous lesion, without lymphoid lesion, suggesting a sexually acquired infection. Eight years later, the complete resolution of the lesion without any treatment is a strong argument against a malignant lymphoid process and raises doubts as to the reality of isolated anorectal HL in immunocompetent participants.

Rare anorectal neoplasms: gastrointestinal stromal tumor, carcinoid, and lymphoma

Several uncommon tumors occur in the anal canal such as gastrointestinal stromal tumors, carcinoids, and lymphoma. Increased clinical experience and advancements in molecular biology have improved the accuracy of pathologic diagnosis and guided treatment recommendations, which the author addresses in this article.

Colorectal lymphoma in the setting of HIV: case report and review of the literature

The incidence of Burkitt's lymphoma, a rare and aggressive form of non-Hodgkin's lymphoma, remains unaffected by immune reconstitution in HIV-infected individuals. We report a case of a 45-year-old patient with HIV on highly active antiretroviral therapy (HAART) who presented with symptoms of rectal pain. After two misdiagnoses, a computed tomography (CT) scan showed marked rectal wall thickening and lymphadenopathy. A flexible sigmoidoscopy with biopsy of the rectum and peripheral blood smear with bone marrow examination revealed immunophenotypic and cytogenic findings diagnostic of Burkitt's lymphoma of the rectum. The patient has initiated an intensive chemotherapy regimen with good clinical response. There have been significantly fewer reports of colorectal lymphomas in the HAART era, although HIV-infected patients are still at higher risk for developing uncommon manifestations of these types of malignancies.

[Anal and anal margin tumors]

Tumors of the anal canal and anal margin are rare. They may raise specific problems for the pathologist. Benign tumors mainly consist of condylomas, cloacogenic polyps and fibro-epithelial polyps. Cancers are infrequent and consisted of well-differentiated squamous cell carcinoma, or poorly differentiated basaloid squamous cell carcinoma. The other malignant tumors are very rare.

Extranodal lymphoma

Lymphomas arising in extranodal sites are intriguing. The types of lymphomas encountered vary widely from one extranodal site to another. For many types of extranodal lymphomas, there are distinctive clinicopathologic features, sometimes including association with an underlying immunodeficiency syndrome, autoimmune disease, infection, or other immunologic disorder, or a predilection to affect patients of certain ethnic origins. Presented below is a review of lymphomas that are encountered most often in extranodal sites.

Rectal burkitt lymphoma in childhood

Lymphomas are the third most common cancer in children and Burkitt lymphoma (BL) accounts for about 40% of them. The rectum is extremely seldom involved in BL: 91 children were treated at our institution for BL between 1987 and June 2006, but none of them had involved the rectum. We report here on a 9-year-old boy who presented with bowel bleeding and subocclusion, which proved due to a BL of the rectum. The role of surgery for this tumor is limited nowadays, except for surgical emergencies, biopsies, and second-look surgery in selected cases.

EBV detection in HIV-related oral plasmablastic lymphoma

OBJECTIVES

Plasmablastic lymphoma (PBL) of the oral cavity is an aggressive neoplasm derived from B cell, considered to be the second more common among human immunodeficiency virus (HIV)-associated malignancies. As Epstein-Barr virus (EBV) infection has been associated with this neoplasm, the aim of the present study was to assess the presence of EBV in 11 cases of oral HIV-related PBL and investigate the controversial issue of the presence of Human herpesvirus-8 (HHV-8) in these tumors.

METHODS

DNA was extracted from nine cases of HIV-associated oral lymphomas, diagnosed as PBL, and genomic material was amplified by polymerase chain reaction to verify the presence of EBV. In situ hybridization (ISH) for EBV was performed in five cases. Immunohistochemical analysis was conducted to confirm previous diagnosis and verify HHV-8 infection.

RESULTS

The 11 cases had diagnosis confirmed by immunohistochemical analysis. Only nine cases presented an adequate amount of DNA for analysis, and EBV was detected in seven of them. The five cases tested for EBV viral infection by ISH showed positive signals. All 11 cases were negative for HHV-8.

CONCLUSION

The presence of EBV in all cases studied favors a direct role of this virus in the development of HIV-related PBL, and this finding could be considered when dealing with HIV patients.

Gastrointestinal malignancies in HIV-infected or immunosuppressed patients: pathologic features and review of the literature

The gastrointestinal (GI) tract is a common internal organ to be involved by human immunodeficiency virus (HIV)-related malignancies. It is the second most common site for Kaposi sarcoma after skin, and the commonest visceral site, for Kaposi sarcoma in AIDS patients. GI lymphomas have been documented in approximately 25% of AIDS patients with systemic lymphomas. Moreover, GI involvement of AIDS-lymphoma has been associated with poor prognosis and short survival. Several other malignancies that occur in the GI tract are also closely related to HIV-infected or immunosuppressed individuals; these include posttransplant lymphoproliferative disorder, Epstein-Barr virus-associated smooth muscle tumors, anal precancerous lesions, and squamous cell carcinoma. As a result of active antiretroviral therapy, patients infected with HIV are living longer and are consequently at increased risk for development of cancer. Therefore, it is possible that the number of AIDS-associated malignancies will rise and the pattern of tumors may change in the future. In this paper, the clinicopathologic features of GI malignancies associated with AIDS patients are reviewed and the differential diagnosis with other mimic lesions is discussed.

The non-Hodgkin lymphomas: a review of the epidemiologic literature

The non-Hodgkin lymphomas (NHL) are a heterogeneous group of B-cell and T-cell neoplasms that arise primarily in the lymph nodes. NHL incidence rates in the US doubled between about 1970 and 1990, and stabilized during the 1990s. NHL accounts for approximately 3.4% of cancer deaths in the US. Although some of the observed patterns in NHL have been related to HIV/AIDS, these conditions cannot fully explain the magnitude of the changes; neither do changes in classification systems nor improved diagnostic capabilities. Studies of occupational and environmental exposures (e.g., pesticides, solvents) have produced no consistent pattern of significant positive associations. Inverse associations with ultraviolet radiation exposure and alcohol and fish intake, and positive associations with meat and saturated fat intake have been reported in several studies; additional studies are needed to confirm or refute these associations. Family history of NHL or other hematolympho-proliferative cancers and personal history of several autoimmune disorders are associated with increased risk of NHL, but are not likely to account for a large proportion of cases. HIV and other infectious agents, such as human herpesvirus 8 and Epstein-Barr, appear to be associated with differing types of NHL, such as some B-cell lymphomas. Future epidemiologic studies should evaluate associations by NHL type, enhance exposure information collected, and elucidate factors that may identify susceptible (or resistant) subpopulations because of genetic, immunologic or other characteristics. The extent to which the etiology of NHL types may differ is important to resolve in ongoing and future studies.

[Ano-rectal symptoms, related to Epstein-Barr Virus-Associated Burkitt's lymphoma in an immunocompetent patient]

We report the case of an immunocompetent 23-year-old Caucasian woman, with symptoms including rectal bleeding, tenesmus and epreint, 6 months after an anal sexual trauma. The rectal examination showed a hardened, inflammatory and painful anal margin, associated with stenosis of the anal canal, suggesting abscess. The neurological examination showed numbing of the chin. Pelvic MRI and CT scan confirmed a bulky posterior tissular pelvic mass more than 7 cm in diameter, infiltrating the rectum and the anal canal. Final diagnosis confirmed by biopsy performed during rectosigmoidoscopy was an Epstein-Barr Virus-Associated Burkitt's lymphoma. Chemotherapy resulted in rapid regression of the tumoral mass.

Poorly differentiated tumours of the anal canal: a diagnostic strategy for the surgical pathologist

Poorly differentiated malignancies affecting the anal canal are uncommon but pose diagnostic difficulties because of the wide range of normal cell types that may occur within a limited anatomical region. The range of lesions that may present as poorly differentiated tumours includes squamous cell carcinoma, adenocarcinoma, small and large cell neuroendocrine carcinoma, neuroendocrine carcinoma expressing epithelial cytokeratins and other patterns of mixed differentiation, undifferentiated carcinoma, malignant melanoma, lymphoma and secondary tumours. This review discusses the differential diagnosis of these neoplasms with the aid of short illustrative case studies.

Anorectal and gastric peripheral T-cell lymphoma, unspecified in a non-AIDS patient

Anorectum is a rare location for malignant lymphoma. Involvement of is rare even for the lynphoma associated with acquired immune deficiency syndrome (AIDS), and AIDS has a relatively increased frequency of anorectal lymphoma. Most lymphomas in AIDS patients are of a B-cell origin, and T-cell lymphoma of the gastrointestinal tract is extremely rare. We report here on a case of anorectal and gastric peripheral T-cell lymphoma, unspecified (PTCLu) in a non-AIDS patient. A previously healthy 29-year-old man presented with hematochezia and tenesmus that he had suffered with for the previous 2 months. Sigmoidoscopy showed anal and rectal submucosal tumor. Multiple round-shaped, flat and elevated lesions were noted on the gastric antrum and body as well. He underwent excisional biopsy for the anal mass and the diagnosis was PTCLu. Biopsies of the gastric lesions gave the same diagnosis. There was no lymphoma involved in the bone marrow. At admission, no antibodies against human immunodeficiency virus were detected. He underwent systemic chemotherapy and upfront autologous stem cell transplantation.

State of the art: gastrointestinal malignancies in the human immunodeficiency virus (HIV) population

The gastrointestinal tract is one of the most common sites for the development of primary neoplasms arising in patients with pre-existing infection with the human immunodeficiency virus (HIV). Over the past decade, new information on the clinical manifestation, natural history, treatment options, and related toxicity have been reported, mostly notably the integration of highly active antiretroviral therapy (HAART). The following is a concise review summarizing the current state-of-the-art for GI tract malignancies in the HIV-positive patient and is designed to assist the clinical oncology team in developing a rationale plan when caring for these patients.

Management of Less Common Tumors of the Colon, Rectum, and Anus

The majority of colorectal and anal malignancies are adenocarcinomas and squamous cell cancers, respectively. Despite the predominance of these neoplasms in these locations, rare histiotypes of the colon, rectum, and anus do occur. These histotypes include but are not limited to lymphoma, melanoma, diffuse cavernous hemangioma, and sarcomas, such as leiomyosarcoma or Kaposi's sarcoma. These tumors often present challenges to clinicians with respect to diagnosis, staging, management, and pathology because of their unfamiliarity. A Medline search using "colon," "rectum,""anus," "lymphoma," "melanoma," "diffuse cavernous hemangioma," "squamous cell carcinoma," "carcinoid," "sarcoma," "leiomyosarcoma," "Kaposi's sarcoma," "Paget's disease," "Bowen's disease," and "basal cell carcinoma" as key words was performed as well as a cross-referencing of the bibliography cited in each work. Rare tumors of the colon, rectum, and anus present diagnostic and management dilemmas for clinicians. Because of their infrequency and poor prognosis, the optimal management of these tumors is controversial. For some histotypes, such as squamous cell carcinoma and carcinoids of the rectum, treatment depends on location and size of the tumor. For uncommon anal lesions, such as Bowen's disease, Paget's disease, and basal cell carcinoma, wide local excision (WLE) with negative margins is the standard of care. For other lesions such as anorectal melanoma or leiomyosarcoma, abdominal perineal resection versus WLE is still being debated. Because the optimal treatment of these tumors is still unclear, we recommend a multidisciplinary approach including a surgeon, primary care physician, medical oncologist, radiation oncologist, and pathologist to offer the patient the best outcome.

HIV-related and Epstein-Barr virus-associated anal Burkitt's lymphoma: report of a case

PURPOSE

This article describes and discusses primary Burkitt's lymphoma of the anus which is an extremely rare site of origin.

METHODS AND RESULTS

A 38-year-old HIV+ Rwandan farmer had an 8-cm x 13-cm anal tumor. Histopathology and immunohistology provided evidence of an Epstein-Barr virus-associated Burkitt's lymphoma. Chemotherapy in combination of virostatic therapy is the gold standard for treatment, but because of economic constraints surgical treatment was the only practicable intervention and an abdominoperineal resection of the anorectum was performed.

CONCLUSIONS

Because of the AIDS epidemic and the increase of anal malignant pathologies, anal Burkitt's lymphoma may appear more frequently. Adequate treatment is available for only a small percentage of patients.

Classical Hodgkin lymphoma arising in the rectum

We report a case of an 81-year-old immunocompetent Mexican man who underwent an abdominal-perineal rectal resection for a mass clinically thought to be carcinoma. Histopathologic diagnosis revealed classical Hodgkin lymphoma, nodular sclerosis type, involving the rectum. The diagnosis was confirmed by immunohistochemical studies that showed that the neoplastic cells were positive for CD15 and CD30 and negative for CD45 (LCA). In situ hybridization for Epstein-Barr virus small-encoded RNA was also positive in the neoplastic cells. Hodgkin lymphoma arising in the rectum of immunocompetent patients is rare, with only 12 cases (including this one) reported in the literature. Of these, the diagnosis was confirmed by immunohistochemical studies in only two cases, and this is the first case assessed and shown to be positive for Epstein-Barr virus.

Investigation of Epstein-barr virus in Chinese colorectal tumors

AIM: To elucidate the association of Epstein-Barr virus (EBV) with colorectal tumors and to demonstrate whether infection of EBV existed in different stages of colorectal tumors involves in the carcinogenesis.

METHODS: One hundred and thirty paraffin-embedded tissues of colorectal tumors were classified into 5 groups: 26 adenomas, 23 adenomas complicated with dysplasia, 22 adenomas complicated with carcinomatous, 36 colon carcinoma and 23 HNPCC, were examined by PCR, IHC and ISH, respectively.

RESULTS: EBV DNA was detected by PCR in 26 cases out of the 130 specimens, including 5 cases of adenomas, 5 adenomas complicated with dysplasia, 5 adenomas complicated with carcinomatous, 7 colorectal carcinoma and 4 HNPCC. IHC detection showed the expression of LMP1 in 7 cases, including 1 adenoma, 1 adenoma with dysplasia, 1 HNPPC, 2 adenomas complicated with carcinomatous, and 2 colorectal carcinomas. The expression of EBER1 detected by ISH was positive in 6 cases, including 1 adenoma with dysplasia, 2 adenomas complicated with carcinomatous and 3 colorectal carcinomas. There were no significant differences among the results of PCR, IHC and ISH in the 5 groups. In all cases of HNPCC, none of the tumor cells showed positive signals of EBER1, but some EBV-positive tumor infiltrating lymphocytes were found in 2 of 23 cases.

CONCLUSION: Our results showed that infection of EBV exists in human colorectal tumors, which indicates that EBV may be involved in the carcinogenesis of colorectal tumors but does not play an important role. The mechanisms need to be clarified further.

[A case of anal Burkitt's lymphoma]

Burkitt non hodgkin lymphoma affects children and young adults. It is endemic in tropical Africa and it has especially facial and abdominal localisations. We report a case of anal localisation in a 22 years-old man, human immunodeficiency virus (HIV), negative aiming to show clinical, therapeutical and evolutive particularities of this exceptional localisation. Only two cases were reported but in HIV positive patients. Perianal abscess was first evoked, but per-operatory findings and histology rectify the diagnosis. Without chemotherapy, the "natural" evolution was rapidly fatal. Despite the efficacy of nowadays protocols, showing 80% of recovery, this observation illustrates the difficulty of malignant affection's management in developing countries caused by diagnostic delay and high cost of chemotherapy.

Primary Burkitt-like lymphoma presenting as a solitary rectal polyp in a child: case report

Primary rectal lymphoma in childhood is rare. We report a case in a 10-year-old boy who presented with rectal bleeding and a single rectal polyp. Histologic examination, immunophenotyping and molecular genetic study of the polyp showed a diffuse B-cell lymphoma, Burkitt-like type. The literature on this topic is reviewed and pathologic examination of childhood rectal polyps is emphasized.

Anorectal manifestations of sexually transmitted infections

Sexually transmitted infections have a wide range of clinical presentations, including involvement of the anal verge, anal canal and rectum. This review focuses on anorectal sexually transmitted infections which may cause diagnostic difficulty when encountered by the coloproctologist. An approach to the diagnosis of a variety of sexually transmitted infections is set out, with a discussion of the role of biopsy and a summary of relevant histopathological findings. The value of early antibiotic treatment is discussed. Problems related to HIV/AIDS are highlighted, as clinical presentation may be atypical in immunosuppressed individuals. Sexually transmitted oncogenic viruses and their role in anal neoplasia are also briefly summarized.

EBV-associated perianal Hodgkin's disease in an HIV-positive individual

Hodgkin's disease (HD) has a higher incidence in HIV-positive individuals. It tends to occur at extranodal sites, frequently exhibits an unfavorable histological type with large numbers of neoplastic cells, and almost invariably harbors Epstein-Barr Virus (EBV). We describe a case of a 33-year-old HIV-positive man who presented with anal pain from a 4-cm mass in the anorectal canal. He had no B symptoms or peripheral lymphadenopathy. A chest X-ray was within normal limits. A biopsy showed an ulcerated mass composed of a mixed infiltrate of lymphocytes, plasma cells, eosinophils, and Reed-Sternberg (RS) cells positive for CD15 and strongly positive for CD30. They were negative for CD45 and CD20. Numerous RS cells and lymphocytes were positive for EBV RNA using the EBER-1 probe. This highly unusual presentation of HD may reflect the greater incidence of anorectal lymphoma and of extranodal HD in the HIV-positive population.

Anorectal lymphoma and AIDS: an outcome analysis

BACKGROUND AND OBJECTIVE

Primary lymphoma of the anus is an extremely rare problem. In patients with the Acquired Immune Deficiency Syndrome (AIDS), there is a marked increase in gastrointestinal non-Hodgkin's lymphomas (NHL). The aim of this study was to evaluate the outcome of patients with anorectal NHL and AIDS.

METHODS

Over an 18-year period, we identified 6 patients with AIDS and primary anorectal NHL. Five were male. All were high-grade B-cell lymphomas and half showed systemic "B" symptoms. Patient's mean CD4 count was 93 (range 8 to 201).

RESULTS

The average life span for those with "B" symptoms was 6.7 months and 16 months for those without symptoms. No benefit was shown from radiation or chemotherapy in those with "B" symptoms. Younger patients and those without systemic constitutional symptoms of lymphoma do better. One patient without "B" symptoms was able to tolerate his radiation and chemotherapy and is disease free at 10 months.

CONCLUSION

Despite traditional non-Hodgkin's lymphoma treatment regimens, our AIDS patients (and those examined in a review of the pertinent literature) with anorectal NHL and "B" symptoms have a poor prognosis. For those without "B" symptoms and who can tolerate the therapy, NHL remission may be obtained.

The Spectrum of Cutaneous Lymphomas in HIV infection: a study of 21 cases

We studied 21 HIV-associated lymphomas with cutaneous presentation to determine whether they showed features of primary cutaneous lymphoma arising fortuitously or whether they represented the cutaneous involvement of AIDS systemic lymphoma. Besides rare mycosis fungoides (n = 3), which shared typical clinicopathologic lesions, nonepidermotropic large-cell lymphomas (n = 18) were predominant. They frequently presented as a solitary nodule or tumor. Seven of the eight large T-cell lymphomas had a CD30-positive (CD30+) phenotype but did not express ALK protein. Overexpression of p53 protein was observed in six cases. Although EBV-EBER transcripts were detected in two of them, LMP1 protein was absent. Except for their original prevalence, the features of these T-cell CD30+ cutaneous lymphomas were the same as in immunocompetent patients. The 10 B-cell cutaneous lymphoma were immunoblastic or centroblastic lymphomas, with a differential expression of BCL-6 and Syndecan. Four of them expressed CD30, EBER-EBV transcripts, and LMP1 and p53 proteins. This B-cell CD30+ EBV+ phenotype contrasts with cutaneous lymphoma in immunocompetent patients. Human herpesvirus 8 was not involved in lymphomagenesis since its sequences were detected in a single patient with Kaposi's sarcoma and Castleman's disease. These lymphomas occurred in severely immunocompromised patients with a low CD4 count. Death was due to immunodepression rather than to lymphoma spread, suggesting avoiding aggressive immunosuppressive treatment in such patients.

Viral infections of the gastrointestinal tract

Acute gastroenteritis is common in adults. It can occur in institutional epidemics or epidemics of food-borne illness; in these cases, caliciviruses are the major cause of the condition. When acute gastroenteritis occurs in nonepidemic form, its causes are less clear. It may be due to caliciviruses or to the less common serotypes of childhood gastroenteritis viruses, such as rotavirus, astrovirus, and adenovirus. The pathogenesis of acute viral gastroenteritis is not completely understood. Old evidence suggests that mild villus damage is responsible, but new evidence indicates that active secretion and motility disturbance may be involved in the production of symptoms. Five common viruses can remain latent in gastrointestinal tissues and produce disease many years after initial infection. Two major herpesviruses, cytomegalovirus and herpes simplex virus, cause ulcerative disease of the gastrointestinal tract. This disease occurs in healthy persons but is more common and more severe in immunocompromised patients. Three other viruses--Epstein-Barr virus, human papilloma virus, and human herpesvirus-8--are implicated in benign and malignant proliferative diseases of the gastrointestinal tract. Epstein-Barr virus has been associated with immunoproliferative disease after transplantation and may also cause small-bowel and colonic lymphoma in healthy adults. It causes most AIDS-related lymphomas. Human papillomaviruses cause anorectal condyloma and anal cancer. Human herpesvirus-8 causes gastrointestinal Kaposi sarcoma.

Lymphoma at uncommon sites

Lymphoma can often present in unusual situations. This article provides a comprehensive review of the literature in which both non-Hodgkin's lymphoma and Hodgkin's disease are discussed.

EBV-associated primary lymphomas in salivary glands of HIV-infected patients

The lymph nodes within and around salivary glands are commonly involved in inflammatory processes, but rarely the site of primary lymphomas. We observed six cases of primary salivary gland lymphoma in HIV-infected patients and studied them in parallel with three cases of primary salivary gland lymphoma unrelated to HIV and three cases of HIV-related salivary gland lymphadenopathies in order to characterize this new entity. We found that all salivary gland lymphomas in HIV-infected patients were of high histologic grade while salivary gland lymphomas unrelated to HIV were predominantly of low grade MALT type. All lymphomas in both categories expressed the B-cell phenotype. Just as HIV-unrelated lymphomas frequently arise on the background of chronic inflammatory lymphoid processes, lesions characteristic of HIV-lymphadenopathy were still present in some lymphomas of HIV-infected patients. EBV RNA transcripts (EBER) were demonstrated in three, and latent membrane protein (LMP) in two of the six HIV-related and in none of the three HIV-unrelated lymphomas. The three EBER-positive lymphomas were of the histologic types known to express the virus in most cases. The presence of HIV in the form of the core protein p24 and envelope glycoprotein gp41 on the dendritic reticular cells of germinal centers was ascertained in the cases of HIV-related lymphadenopathies but also in the coexistent lymphadenopathies of lymphomas. The practical importance of diagnosing the salivary lymphadenopathies and lymphomas associated with the HIV-infection resides in avoiding their misdiagnosis and surgical removal as tumors of salivary glands.