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Table of Contents   
SHORT COMMUNICATION  
Year : 2011  |  Volume : 22  |  Issue : 5  |  Page : 737
Benign hyperplasia of duct-associated lymphoid tissue: Report of a case and review of literature


1 Department of Oral and Maxillofacial Pathology, Dr. Syamala Reddy Dental College, Bangalore, India
2 Dental Lavelle, Bangalore, India

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Date of Submission10-Oct-2010
Date of Decision15-Mar-2011
Date of Acceptance08-Aug-2011
Date of Web Publication7-Mar-2012
 

   Abstract 

Focal lymphoid tissue is ubiquitously present in the oral mucosa and serves as a barrier for entrapment of antigens. The mucosa-associated lymphoid tissue is generally dispersed and sometimes associated with the ducts of the minor salivary glands. Proliferation of the duct-associated lymphoid tissue (DALT) is rarely reported, though probably of common occurrence. We report a case of benign hyperplasia of DALT in the buccal mucosa of a 58-year-old male. The histogenesis and pathological implications of this tissue are discussed and the need for recognition of this entity is stressed.

Keywords: Benign hyperplasia, duct-associated lymphoid tissue, mucosa-associated lymphoid tisssue

How to cite this article:
Kamath VV, Belur J. Benign hyperplasia of duct-associated lymphoid tissue: Report of a case and review of literature. Indian J Dent Res 2011;22:737

How to cite this URL:
Kamath VV, Belur J. Benign hyperplasia of duct-associated lymphoid tissue: Report of a case and review of literature. Indian J Dent Res [serial online] 2011 [cited 2020 Aug 9];22:737. Available from: http://www.ijdr.in/text.asp?2011/22/5/737/93477
Minor salivary glands (MSG) are a common histological entity in the oral mucosa. Islands of focal lymphoid tissue are also scattered in the submucosa and these may or may not be associated with the MSG. Such islands are variously called mucosa-associated lymphoid tissue (MALT) and are seen as immunological barriers in the protection of the oral mucosa. Duct-associated lymphoid tissue (DALT) is a part of the MSG lymphoid tissue and have been infrequently reported in the literature. They are periductally oriented, either diffuse or arranged in follicles, and are seen in the submucosa of humans and nonhuman primates. We report a case of a 58-year-old male presenting with a painless swelling of the right cheek, which when biopsied showed proliferation of DALT. The recognition of this entity and the awareness of the fact that it may be involved in pathological processes involving the mucosal tissue, gland, and the lymph nodes should be noted.


   Case Report Top


A 56-year-old male reported to the clinic with complaints of a slowly growing lesion in his right cheek which had been noticed about 6 months prior to the present consultation. The patient had sought referral to a dentist who had diagnosed the lesion as a mucocoele and advised him to avoid catching his cheeks during mastication. Due to non-resolution and continual growth the patient sought a referral to our clinic. The patient was intensely cancerophobic. There were no habits and the medical history was not significant. Oral examination revealed a freely mobile mass of about 3 cm × 2 cm on the right cheek in the "occlusal line" apposing the premolars. The lesion was sessile, with normal mucosal texture and no signs of surface ulceration at time of diagnosis. There were white keratotic changes around the lesion more indicative of frictional keratosis. The patient was asymptomatic. There was no evidence of any localized lymphadenopathy. Under a local anesthesia the lesion was excised. During the surgical procedure, the lesion was found to have a sharp demarcation with the rest of the connective tissue and an enucleation was possible. Primary closure was achieved and the mass sent for histopathological examination. The tissue revealed focal, well-organized proliferation of lymphocytes in a matrix of sparse connective tissue [Figure 1]. The lymphocytes were densely packed and showed focal aggregation resembling germinal centers in many areas. Admixed among these lymphocytes were ducts of MSG with evidence of hyperplasia [Figure 2] and [Figure 3]. There was evidence of ductal proliferation though benign in nature [Figure 3]. No abnormality of the lymphocytes was observed [Figure 4]. The histological picture was of a localized hyperplasia of lymphoid tissue with entrapment of salivary ducts. A diagnosis of "benign hyperplasia of DALT" was returned. The patient was followed up for about a year and has shown an uneventful recovery.
Figure 1: Photomicrograph of associated lymphoid tissue showing architecture and composition similar to a lymphoid follicle, characteristic of mucosa-associated lymphoid tissue (H and E, 10)

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Figure 2: Photomicrograph of a lesion showing periductal proliferation of lymphocytes (H and E, ×10)

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Figure 3: High-power view of ducts entrapped in the lymphoid tissue with evidence of hyperplasia (H and E, ×40)

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Figure 4: High-power view of the lymphoid component showing the typical architecture of a reactive lymphnode (H and E, ×40)

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   Discussion Top


DALT, a part of normal MSG lymphoid tissue, has frequently been reported in various sites of the oral mucosa in man and nonhuman primates. [1],[2],[3],[4] These usually tend to be oriented periductally in the form of follicles or nodules. A close association between the oral mucosal lymphoid tissue and the secretory ducts of MSG has been noted by earlier [2] and recent authors. [3],[4],[5] Animal studies have shown that stereologically, DALT occupies a volume of 1-5% of the extraepithelial mucosal tissue at labial, buccal, [5] and soft palatal [3] sites in young adult monkeys. No such studies have been recorded on humans. There is also evidence, in animal studies, that this volume tends to decline with increasing age. [6],[7],[8]

As with MALT, DALT is totally absent in newborn (monkeys), begins to appear in early life, shows a rapid increase in volume during the growth period and eventually undergoes involution or pathological alterations. [6] This was strongly suggestive of an age-dependent and antigen-induced nature of these structures. [7] Scott [9] reported a similar decline in the prevalence of focal collections of lymphoid tissue of MSG in clinically healthy subjects. Though various reports exist in the literature regarding the occurrence of DALT in humans no systematic studies or case reports have been encountered of pathological entities associated with this structure. This may be largely due to the fact that the structure has probably been more underrecognized and underdiagnosed than its presence would suggest.

Schroeder et al.[8] have described in detail the architecture and structural organization of DALT. By means of serial sectioning and tissue reconstruction methods, DALT of simian MSG was rebuilt three-dimensionally. A typical unit consisted of organized lymphoid tissue existing in juxtaposition to a secretory duct portion. Most of them were located within MSG nodules, preferably at the confluence of interlobular ducts, but could also be encountered subepithelially in the lamina propria, along the course of main secretory ducts and immediately underneath the oral epithelium. Each unit was about 0.05-0.1 mm in size and often included well-defined germinal centers. The latter sometimes embraced particular blind, pouch-like duct formations protruding into the lymphoid tissue, which resembled tonsillar microcrypts. The follicle-related aspect of the duct wall was heavily infiltrated by mononuclear cells, which come in contact with luminal contents. In fact, clusters of Gram-negative bacteria could be encountered in those deep-seated luminal portions. [4],[8]

Any antigenic stimulus to the oral mucosa would have the submucosal groups of lymphoid tissue mounting an immune response. Hyperplasia of lymphoid tissue is a classic reaction of the tissue to antigenic stimulus. The present case involved a perceptible swelling secondary to a known stimulus of cheek biting. The histological picture was very interesting in that the diffuse proliferation of the lymphoid follicles did not involve the ducts, which showed a normal histology albeit with mild signs of ductal cell hyperplasia. The occurrence of such a pathological process associated with DALT has hitherto not been reported in the literature.

In an excellent discussion on the development of DALT and its response to antigenic stimuli, Nair and Schroeder [4] postulate that the development of MALT is primarily linked to antigenic stimulus. MSG of newborn animals neither show the presence of DALT nor do they contain interacinar plasma cells. MALT is known to be minimal at birth, and animals kept under germ-free conditions are said to show little development of MALT and germinal centers. The development of MALT with germinal centers occurs with colonization of the GI, respiratory and urogenital tracts with bacterial flora. Subsequent to this development there is an entry by retrograde passage of the antigens into the ducts of the MSG. [9] Stray or antigen seeking lymphocytes, known to be present in the ducts, due to repeated stimulation then proliferate resulting in the formation of DALT. [10],[11],[12] The authors also emphasize that lymphoid lesions of MSG encountered in disease conditions seem to have no particular affinity for the glandular duct system. In fact, the entire glandular parenchyma becomes infiltrated by varying degrees of both focal and diffused collections of lymphoid cells which ultimately destroy the glandular parenchyma. In other words, chronic stimuli for lymphoid activation with characteristic MSG and other exocrine glandular manifestations in those disease conditions appear to be systemic and autogenous when compared to that of DALT which is primarily topical and exogenous in nature. [13] The occurrence of the pathological swelling in the present case seems to bear this supposition.

Structurally and functionally speaking, DALT therefore has to be considered as an integral part of GALT, the development of which depends on topical and exogenous antigenic stimuli. DALT, thus being an integral part of GALT, probably plays a substantial role in the secretory immunoglobulin-mediated immunity of the oral cavity.

 
   References Top

1.Bickel G. Ueber die Ausdehnung und den Zusammenhang des lympatischen Gewebes in den Rachengegend. Virchows Arch Path Anat Physiol 1884;97:340.  Back to cited text no. 1
    
2.Nadler J. Zur Histologie der menschlichen Lippendrusen. Arch Mikrosk Anat 1897;50:419.  Back to cited text no. 2
    
3.Klein PB, Weilenmann WA, Schroeder HE. Structure of the soft palate and composition of the oral mucous membrane in monkeys. Anat Embryol 1979;156:197.  Back to cited text no. 3
    
4.Nair PN, Schroeder HE. Architecture of minor salivary gland duct and lymphoid follicle associations in Macacafascicularis. Cell Tissue Res 1985;240:223.  Back to cited text no. 4
[PUBMED]    
5.Ciccone E, Truini M, Grossi CE. Lymphoid complement of the human salivary glands: Function and pathology. Eur J Morphol 1998;36(Suppl):252-6  Back to cited text no. 5
    
6.Schroeder HE, Dorig-Schwarzenbach A. Structure and composition of the oral mucous membrane on the lip and cheek of the monkey Macacafascicularis. Cell Tissue Res 1982;24:89.  Back to cited text no. 6
    
7.Nair PN, Zimmerli I, Schroeder HE. Minor salivary gland duct-associated lymphoid tissue (DALT) in monkeys changes with age. J Dent Res 1987;66:407-11.  Back to cited text no. 7
[PUBMED]  [FULLTEXT]  
8.Schroeder HE, Dorig-Schwarzenbach A. Age-related decline of lymphoid-tissue components in the oral mucosa of the lip cheek and soft palate of Macacafascicularis. Cell Tissue Res 1984;235:195.  Back to cited text no. 8
    
9.Scott J. Qualitative and quantitative observations on the histology of human labial salivary glands obtained post mortem. J Biol Buccale 1980;8:187.  Back to cited text no. 9
[PUBMED]    
10.Schroeder HE, Moreilon MC, Nair PN. Architecture of minor salivary gland duct/lymphoid follicle associations and possible antigen-recognition sites in the monkey Macacafascicularis. Arch Oral Biol 1983;28:133.  Back to cited text no. 10
    
11.Nair PN, Schroeder HE. Retrograde access of oral antigens into minor salivary glands in the monkey Macacafascicularis. Arch Oral Biol 1983a;28:145.  Back to cited text no. 11
[PUBMED]    
12.Nair PN, Schroeder HE. Local immune response to repeated topical antigen application in the simian labial mucosa. Infect Immun 1983b;41:399.  Back to cited text no. 12
[PUBMED]  [FULLTEXT]  
13.Nair PN, Schroeder HE. Duct-associated lymphoid tissue (DALT) of minor salivary glands and mucosal immunity. Immunology 1986;57:171-80.  Back to cited text no. 13
[PUBMED]  [FULLTEXT]  

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Correspondence Address:
Venkatesh Vishwanath Kamath
Department of Oral and Maxillofacial Pathology, Dr. Syamala Reddy Dental College, Bangalore
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.93477

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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