9: Lymphoid Lesions

Lymphoid Lesions

Reactive Lesions

In this chapter, three primary groupings of lesions—reactive, developmental, and neoplastic—are considered. An important point in the discussion of lymphoid lesions involving the oral cavity and adjacent areas is that many lesions, especially those arising in lymph nodes, are capable of simulating malignancy.

Lymphoid Hyperplasia

It is sometimes difficult to distinguish reactive from neoplastic lymphoid proliferations, especially when they occur in unusual sites such as the peritonsillar area, palate, buccal mucosa, lymph nodes, and salivary glands. The incidence of benign cystic lymphoepithelial lesions within the parotid and submandibular glands is increasing in patients with acquired immunodeficiency syndrome (AIDS).

One of the normal sites of lymphoid tissue is the posterolateral portion of the tongue. Aggregations of lymphoid tissue within this area are part of the foliate papillae, or lingual tonsil. They may be distinguished from other lymphoid tissues by deep crypts lined by stratified squamous epithelium. These papillae occasionally become inflamed or irritated, with associated enlargement and tenderness. In such instances, patients may become symptomatic. On examination, these areas are enlarged and somewhat lobular in outline, with an intact overlying mucosa and prominent superficial vessels. In instances in which such lesions are removed for diagnostic purposes, the chief finding is reactive lymphoid hyperplasia. Within the enlarged germinal centers, mitoses and macrophages containing cellular debris may be seen. In addition to the foliate papillae, other zones where lymphoid tissue is found include the anterior floor of the mouth on either side of the lingual frenum, the anterior tonsillar pillar, and the posterior portion of the soft palate (Figures 9-1 and 9-2). Because lymphoid tissues are not always found in these areas, they are usually regarded as ectopic. The term oral tonsil also refers to this tissue.

Reactive lymphoid hyperplasia (oral tonsil) has male predominance and is noted within the second and third decades of life. In one study, a mean age of 23 years was found. Lesions range from 1 to 15 mm in diameter and may persist for years.

The buccal or facial lymph node is often the site of a reactive hyperplastic process. This is characterized as a freely movable submucosal nodule in the buccal mucosa that is usually adjacent to the second premolar and first molar teeth and can often be palpated extraorally. The cause of the process is unknown, but it may be a reaction to irritation or localized trauma. Gingivitis or periapical pathology may occasionally stimulate or initiate enlargement of this particular lymph node.

Management should be directed toward elimination of the cause of the problem if it can be identified, followed by simple observation.

Follicular lymphoid hyperplasia may be seen in the palate. This reactive polyclonal proliferation of lymphocytes is often difficult to separate from lymphoproliferative disease of the palate, a condition that may signify lymphoma. Histologically, follicular lymphoid hyperplasia of the palate is characterized by irregularly sized, well-demarcated germinal centers with a crisply defined rim or mantle of small, mature lymphocytes. Within the germinal centers, macrophages contain phagocytosed nuclear debris. Using immunohistochemical techniques, a mixture of kappa and lambda light chains (B lymphocytes) is seen, indicating a polyclonal population of cells. In addition, the mantle zones are composed of both mature and immature B cells, whereas the extramantle zones contain both B and T lymphocytes, plasma cells, macrophages, and eosinophils. Indefinite follow-up is prudent because of possible progression to lymphoma.

Epithelioid Hemangioma (Angiolymphoid Hyperplasia With Eosinophilia)

Epithelioid hemangioma, also known as angiolymphoid hyperplasia with eosinophilia (ALHE), was first described in 1948 as a nodular subcutaneous benign disease in young men. Later, however, cases with the same clinical and histologic features were reported in the oral cavity. In addition to nodular aggregates of lymphocytes and eosinophils, regional lymphadenopathy and blood (peripheral) eosinophilia were noted. Similar findings were noted under the headings of Kimura’s disease, eosinophilic granuloma of soft tissue, and eosinophilic lymphofolliculosis. Because Kimura’s disease was originally described as having a distinct male predilection without associated regional lymphadenopathy, some clinicians believe that the two conditions represent different entities. Histologically, some differences have been described, adding to the tendency to split ALHE and Kimura’s disease into two separate but related entities.

Developmental Lesions

Lymphoepithelial Cyst

Lymphoepithelial cyst is an uncommon lesion of the mouth, major salivary glands, or neck that is thought to arise from an entrapment of epithelium within lymph nodes or lymphoid tissue during development. Subsequent epithelial proliferation results in a clinically evident mass.

Oral lymphoepithelial cysts (see also the discussion on ectopic lymphoid tissue in Chapter 3) present as asymptomatic mucosal elevations that are well defined and yellowish pink (Figure 9-3). The site most commonly affected is the floor of the mouth, where approximately 50% of cases are found. Ventral and posterolateral portions of the tongue constitute an additional 40% of cases; the balance is shared among the soft palate, the mucobuccal fold, and anterior facial pillars. A wide age range is noted, from adolescence to the seventh decade of life. The gender distribution is essentially equal. Except for the small central cystic space, these lesions are identical to ectopic lymphoid aggregates.

A marked increase in the incidence of lymphoepithelial cysts of the major salivary glands has been noted recently, particularly in those testing positive for the human immunodeficiency virus (HIV). The mechanism of cyst formation is unclear.

Neoplasms

Lymphoma

Lymphomas are malignant neoplasms of component cells of lymphoid tissues. Broad division of the group into Hodgkin’s and non-Hodgkin’s lymphomas is widely accepted. Hodgkin’s lymphoma is primarily a disease of lymph nodes characterized by the presence of large binucleated cells called Reed-Sternberg cells and a lymphoid stroma composed of large numbers of non-neoplastic cells. Hodgkin’s lymphoma is very rare in the oral cavity.

Non-Hodgkin’s Lymphoma

Non-Hodgkin’s lymphomas (NHLs) are a relatively common group of neoplasms (more than 50,000 cases per year) that often occur in extranodal head and neck sites, especially in HIV-infected (AIDS) patients. NHLs are heterogeneous with a spectrum of behaviors. Some cases are indolent but ultimately fatal; others are aggressive and if left untreated kill the patient rapidly. NHL can arise in lymph nodes (nodal) and extranodal sites. Up to 40% of all NHLs arise at extranodal sites, with the most common site being the gastrointestinal tract. In the West, they most commonly occur in the stomach, but in the Middle East, the intestine is the most common location. The head and neck is the second most common site for extranodal NHL; most cases arise in Waldeyer’s ring.

Similar to lymphomas arising in lymph nodes, B-cell lymphomas are the most common phenotype in extranodal sites. A wide histologic and biological spectrum of B-cell lymphomas occur in the head and neck. Although most are diffuse large B-cell lymphomas, other types are seen in specific sites and populations of patients. These include Burkitt’s lymphoma occurring in the facial bones of young patients and T-cell and natural killer cell lymphomas in the nasofacial region, producing the clinical condition termed midline granuloma. A large proportion of lymphomas arise within lymph nodes embedded in the salivary tissues. Lymphomas may also arise within salivary gland parenchyma; they resemble those arising in mucosa-associated lymphoid tissue (MALT). This group of tumors, now known as extranodal marginal zone lymphomas, is genotypically and phenotypically unique and is characterized by a relatively long and indolent natural history.

Classification

The microscopic classification of NHL continues to evolve. At least eight classifications have been proposed over the past 30 years, but none have gained universal acceptance. The current and most widely adopted system is that from the World Health Organization (WHO) (Table 9-1), which is based on a prior system known as the Revised European American Lymphoma (REAL) scheme. This scheme divides lymphomas into T- and B-cell groups and includes a number of entities that arise at extranodal sites. This system focuses on distinct biological entities defined by a combination of clinical, morphologic, immunophenotypic, and genotypic features. It has been shown to be highly reproducible and clinically relevant. Moreover, because it is a list of entities, new lymphomas can be added when they are identified and characterized. Both the WHO and REAL classification systems have been criticized for their heavy reliance on immunohistochemical phenotyping and their problematic application when clinical information is missing or limited. Moreover, because both systems provide a list of entities without biological groupings, learning the systems can be difficult.

TABLE 9-1

MODIFIED WHO CLASSIFICATION OF LYMPHOMAS

  B-Cell Neoplasms T-Cell and Postulated NK-Cell Neoplasms
Precursor cell neoplasms Precursor B-lymphoblastic lymphoma/leukemia Precursor T-lymphoblastic lymphoma/leukemia
Peripheral (mature) cell neoplasms B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (B-CLL/SLL) T-cell chronic lymphocytic leukemia
  Lymphoplasmacytoid lymphoma Large granular lymphocytic leukemia (T-cell or NK-cell type)
  Mantle cell lymphoma Mycosis fungoides
  Marginal zone B-cell lymphoma (extranodal or nodal) Peripheral T-cell lymphoma, unspecified
  Splenic marginal zone B-cell lymphoma Angioimmunoblastic lymphoma
  Hairy cell leukemia Intestinal T-cell lymphoma
  Plasmacytoma Adult T-cell lymphoma/leukemia
  Diffuse large B-cell lymphoma Anaplastic large cell lymphoma
  Burkitt’s lymphoma  

NK, Natural killer.

Etiology

Little is known about the origin of NHL. Variations in incidence in different ethnic groups suggest a strong genetic predisposition. Immunodeficiency, whether acquired or congenital, is an important risk factor for the development of some lymphomas and may be related to a defective immune response to the Epstein-Barr virus (EBV), permitting clonal expansion of infected cells. Some lymphomas are clearly associated with specific chromosome translocations such as t(8;14), t(8;22), and t(2;8) in Burkitt’s lymphoma and t(11;14) in mantle cell lymphoma (Table 9-2). These specific chromosome translocations result in the dysregulation of oncogenes or tumor suppressor genes, producing unregulated cell proliferation. Why specific translocations occur is not known.

TABLE 9-2

CHARACTERISTIC CYTOGENETIC FINDINGS IN SELECTED, SPECIFIC LYMPHOMAS

Lymphoma Type Translocation Oncogene or Tumor Suppressor Genes Mechanism
Follicular lymphoma t(14;18) Bcl-2 Juxtaposition of Bcl-2 with IgH promoter results in overexpressed antiapoptotic protein Bcl-2
Extranodal marginal zone t(11;18) AP12, MLT Chimeric protein that inhibits apoptosis Juxtaposition of lymphoma Bcl-10 with IgH promoter results in overexpressed Bcl-10 protein
t(1;14) Bcl-10
Mantle cell lymphoma t(11;14) Bcl-1 (cyclin D1) Juxtaposition of Bcl-1 with IgH promoter results in overexpressed cyclin D1 protein
Burkitt’s lymphoma t(8;14)
t(8;22)
t(2;8)
c-Myc Overexpression of Myc is due to juxtaposition of the c-Myc gene with IgH, Igκ, or Igλ
Anaplastic large cell lymphoma t(2;5) NPM, ALK Production of chimeric NPM, ALK protein, which has lymphoma tyrosine kinase activity

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Ig, Immunoglobulin.

Staging

The importance of proper staging (determining the clinical extent of disease) for patients with lymphoma in the oral region cannot be overemphasized. Staging serves a number of important purposes, including determination of the type and intensity of therapy, the overall prognosis for the patient, and potential complications associated with the disease. The Ann Arbor method, although initially designed to stage Hodgkin’s lymphoma, is now widely used for NHL (Box 9-1). Generally, patients are assigned a stage between I and IV depending on the site and extent of their tumor. In addition, patients are classified as “A” (no symptoms) or “B” (constitutional symptoms).

The staging procedure often differs according to the type and site of lymphoma. Gastrointestinal assessment is performed for lymphomas of Waldeyer’s ring because these tumors are often accompanied by gastrointestinal involvement. Extranodal marginal zone lymphoma tends to remain localized for prolonged periods and has a relatively indolent clinical course, hence less extensive investigation is often required. Assessment of the central nervous system (CNS) is performed for lymphomas of the nose and paranasal sinuses, and for lymphoblastic lymphoma and undifferentiated types. Bone marrow biopsy is generally performed for all extranodal lymphomas of the head and neck, but staging laparotomy is rarely done because visceral organ involvement is unlikely.

Clinical Features

Clinically, three broad groups of NHLs can be discerned on the basis of biological behavior (Table 9-3). These lymphomas may be indolent, aggressive, or highly aggressive. Indolent lymphomas are characterized by slow growth, wide dissemination at presentation, a long natural history, and relative incurability. By contrast, aggressive and highly aggressive groups are characterized by rapid growth, frequent localized presentation, a short natural history, and frequent responsiveness to chemotherapeutic agents. Paradoxically, the most aggressive lymphomas are the ones most likely to be cured. Most lymphomas in adults are diffuse B-cell lymphoma or follicular lymphomas, which together make up more than 50% of all types. Follicular lymphoma is predominantly a tumor of lymph nodes and rarely occurs in the oral cavity. By contrast, T-cell lymphomas are considerably less common at all sites, including the oral cavity. In children, aggressive and highly aggressive lymphomas are the most common, with Burkitt’s lymphoma accounting for more than 40% of types.

TABLE 9-3

COMPARISON OF FEATURES OF INDOLENT, AGGRESSIVE, AND HIGHLY AGGRESSIVE LYMPHOMAS

  Indolent Aggressive Highly Aggressive
Examples of types Follicular lymphoma B-CLL/SLL
Mantle cell lymphoma
Diffuse B-cell lymphoma
Peripheral T-cell lymphoma
Burkitt’s lymphoma
Age Adults Any Children, young adults
Stage at presentation High (>80% stages III and IV) Any High
Tumor growth rate Slow; proliferative fraction is low Fast Very fast; proliferative fraction >95%
Bone marrow involvement Yes Uncommon Common
Natural history if untreated Indolent, usually takes years to kill patient Patient death in 1 to 2 years Patient death in weeks to months
Response to treatment Poor Responsive Very responsive

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B-CLL/SLL, B-Cell chronic lymphocytic leukemia/small lymphocytic lymphoma.

Modified from Chan JKC: Chapter 21. In Fletcher CDM: Diagnostic histopathology of tumors, ed 2, London, 2000, Churchill Livingstone.

The clinical presentation of lymphomas of the oral region varies with their site of origin and tumor type, but most present as a mass or an ulcerated mass and resemble squamous cell carcinoma or salivary neoplasm. Other lymphoid malignancies, such as plasmacytoma and Burkitt’s lymphoma, show a striking predilection for primary involvement of bone. The microscopic characterization of specific lymphoma types is important because staging procedures and therapy may differ for each type. The only reliable method of distinguishing and characterizing these lesions is by immunophenotyping with the use of tissue-based immunologic studies or by flow cytometry of material obtained by fine-needle aspiration. Lymphomas arising within the oral cavity account for less than 5% of oral malignancies. In the head and neck, lymphomas may be />

Jan 12, 2015 | Posted by in Oral and Maxillofacial Pathology | Comments Off on 9: Lymphoid Lesions
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