Oral Extranodal Non Hodgkin ’ s Lymphoma : Series of Forty Two Cases in Malaysia

Lymphoma is a malignant neoplasm of the lymphoid tissue; it is broadly classified into Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) depending on the presence or absence of the Reed-Sternberg cells. Non-Hodgkin lymphoma is further sub classified into B or T-cell types. Generally NHL is more common than HL representing about 92.1%, of these; the B-cell type accounts for 75% (Sukpanichnant, 2004). In the oral cavity NHL represent only 3.5% of all oral malignancies (Epstein et al., 2001). In this study we report a series of 36 cases of oral extranodal NHL and sub classify them into the B-cell and T-cell type. Lymphomas usually involve lymph nodes; however 24% of the NHL occur in extranodal sites, quarter of these occur in the head and neck region (Piatelli et al., 1997). In a study of 1467 cases of NHL; 28% were found in head and neck (Freeman et al., 1972). Extranodal NHL is uncommon in the oral cavity with a percentage range from 2% (Freeman et al., 1972) to 8% (Shah et al., 2011), and often involves the central nervous system (Padhi et al., 2012).


Introduction
Lymphoma is a malignant neoplasm of the lymphoid tissue; it is broadly classified into Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) depending on the presence or absence of the Reed-Sternberg cells.Non-Hodgkin lymphoma is further sub classified into B or T-cell types.Generally NHL is more common than HL representing about 92.1%, of these; the B-cell type accounts for 75% (Sukpanichnant, 2004).In the oral cavity NHL represent only 3.5% of all oral malignancies (Epstein et al., 2001).In this study we report a series of 36 cases of oral extranodal NHL and sub classify them into the B-cell and T-cell type.
Lymphomas usually involve lymph nodes; however 24% of the NHL occur in extranodal sites, quarter of these occur in the head and neck region (Piatelli et al., 1997).In a study of 1467 cases of NHL; 28% were found in head and neck (Freeman et al., 1972).Extranodal NHL is uncommon in the oral cavity with a percentage range from 2% (Freeman et al., 1972) to 8% (Shah et al., 2011), and often involves the central nervous system (Padhi et al., 2012).

Materials and Methods
Selected cases (42 cases) diagnosed as Non-Hodgkin's lymphoma (NHL) during the period of 1980 to 2012 were retrieved from the archives of the Oral Pathology Diagnostic Laboratory, Faculty of Dentistry, University of Malaya.Only cases with complete demographic and site data were selected.Clinical data of these patients were obtained from the clinical files.New sections were made and stained with Hematoxylin and Eosin (H and E) and first examined by one of the author (RBZ).They were subsequently reconfirmed as lymphoma by immunopositivity to leukocyte common antigen (LCA) and the proliferation index was measured by Ki-67.Thirty six cases had sufficient material for further immunophenotyping into T-or B-cell categories.The T-cell phenotype was determined by tumor cell expression of CD3 or CD45O and the absence of B-cell antigens CD20 (L26), or CD79a, and B-cell phenotype determined vice versa.

Results
This series consisted of forty two patients with the diagnosis of extranodal NHL of the oral cavity.The clinical and pathological data of all cases are shown in Table 1.The majorities were males (24 cases) and the rests were females (18 cases), with a male: female ratio of 1.3:1 Their ages ranged from 2 to 90 years old with a mean age of 41.6 years and median age of 47  years.The cases were almost equally distributed between Malay (19) and Chinese (18), and the rest were made of Indian (3 cases) and 2 Indonesians.
The mandible (9 cases) was the most commonly involved site with NHL, followed by the cheek (8 cases) then the palate and maxilla (7 cases each).Four cases were in the salivary glands, and one of them involves both the parotid and submandibular glands.Three of the salivary gland tumors were in Malay.Soft palate and gingiva constitute ywo cases each.And one case for tongue, lip, and foor of the mouth.
Most patients reported with painless progressive swelling.One of the patients (case no.18) had a recurrent NHL which had been treated with chemotherapy; and another patient (case no. 1) had a metastatic tumor in the mandible with the primary tumor in the thymus and thoracic vertebrae.Immunohistochemical examination was performed in 36 of the 42 cases, and more than two third (26 case) were diagnosed as B-cell lymphoma of these 6 cases (23.07%) were Burkitt's lymphomas and only ten cases were diagnosed as T-cell lymphoma, with three cases of NK/T-cell lymphoma.
There was equal distribution of the B-cell lymphomas between males and females (13 case each), however 8 out of the ten cases of T-cell lymphomas were in males (Table 2).About 60% of the T-cell lymphomas were in Chinese, while the B-cell lymphomas was frequently encountered in Malay (46%) and the two Indian cases were B-cell lymphomas.The mean age of the B-cell lymphomas (46.2±24) is higher than the T-cell lymphomas (38.9±22).Four cases with Burkitt's lymphomas were below 15 years old and two patients over 60 years old.
About 66.6% of the lesions were in the soft tissue, of these 70.8% were of the B-cell phenotype.All the seven mandibular, and the two gingival tumors were of the B-cell type.Nine out of the ten T-cell lymphomas were equally distributed between the palate, the maxilla, and the cheek (3 cases each).There were only three NK/T-cell lymphomas in this series; two of wich occurred in the hard palate.There was one rare case of lymphoma of the tongue however, the exact phenotype of this patient was not determined due to insufficient tissue.
B-cell lymphoma: The cases of the B-cell phenotype show a diffuse infiltration of malignant cells with scanty cytoplasm; these cells are small round with dark nuclei and occasional mitosis in few cases (case no. 10, 18, and 19), the remainder of the cases demonstrates a medium to large size cells with round to oval nuclei and vesicular nuclei, prominent nucleoli, and frequent mitosis.Four cases (case no. 12, 29, 31, and 40) of the large cell type were Bcl-2 positive, CD10 and cyclin D1 negative, this allow further classification as diffuse large B-cell lymphoma.
The histopathology of the Burkitt's lymphoma cases (case no. 2, 8, 26, 27, 30, and 39) shows diffuse infiltrating sheets of uniform small neoplastic cells, with a thin rim of cytoplasm.The nuclei of these tumor cells were noncleaved, round with several prominent nucleoli.Mitoses were abundant together with interspersed histiocytes imparting the classical starry sky appearance (Figure 1).Diffuse LCA and CD20 immunoreactivity, and very high Ki-67 labeling index were also observed.

T-cell lymphoma
The seven cases of T-cell type show a diffuse infiltration by small round cells with minimal cytoplasm and dark staining nuclei.However the NK/T-cell cases (case no.17, 28, and 41) demonstrates large pleomorphic cells with hyperchromatic nuclei and angiocentric features.
approximately 2-5% of salivary gland neoplasms and Triantafillidon et al. ( 2012) reported 41% (24 cases) involving the salivary glands.Parotid gland was the most frequently affected among the salivary glands (Weber et al., 2003).In this study, three cases were in the submandibular gland with one case involving both the submandibular and parotid gland.Previous report stated that the buccal mucosa were rarely involved by NHL (Handlers et al., 1986;Howell et al., 1987;Zanakis et al., 1992) however in this series 19.1% of the cases were in the cheek.
The majority of the oral cavity lymphomas are of B-cell type, Kemp et al. (2008) reported a 98% in their study as B-cell lymphomas while, van der Waal et al.( 2005) found all his patients to be of the B-cell type however, in the present we report 72.2% to be of B-cell origin.
An EBV-associated lymphomas that occurs commonly in Chinese is Burkitt's lymphoma which in a previous study from University Malaya accounted for 100% occurrence in this group (Peh, 2001), nevertheless in this study; 3 of the cases occur in Malay and two cases were in Chinese and one case in Indian ethnicity.Burkitt's lymphoma is a high-grade, aggressive type of NHL, it accounts for 3-5% of all lymphomas (Solomides et al., 2002).Three subtypes of Burkitt's lymphoma have been recognized: (1) African (endemic) Burkitt's lymphoma; (2) American (sporadic) Burkitt's lymphoma; and (3) HIV-associated Burkitt's lymphoma.In endemic regions; Burkitt's lymphoma accounts for nearly half of all childhood malignancies (Solomides et al., 2002).In this study 6 cases were diagnosed as Burkitt's lymphoma, four of them (66.6%)occured in patients ≤15 years of age and accounts for 36.4% of all children in this study, this comes in line with an earlier Malaysian study of childhood malignancies which stated that Burkitt's lymphoma is the second most common lymphoma in children (Peh et al., 2004).
Only 8% of oral extranodal lymphomas were of the T-cell type (Epstein et al., 2001;Solomides et al., 2002), however the percentage of T-cell lymphomas in this series is quite high (27.8%), of these 60% were in Chinese.The reason for this high percentage is unknown but may be due to that 43.9% of the cases in this series were Chinese and it is reported that there is a higher prevalence of EBVassociated lymphomas namely NK/T-cell lymphoma in the Chinese when compared to other ethnic group (Howell et al., 1987).
The mainstream treatment of diffuse large B-cell lymphoma is chemotherapy.The CHOP regimen is most widely used which consists of cyclophosphomide, hydrodaunorubicin, vincristin and prednisolone.It is given in either 2, 3 or 4 weekly cycles for 6 to 8 courses.The R-CHOP regimen includes anti-CD20 (rituxianab) which improves the cure rate.Combined radiotherapy along with chemotherapy may be optimal therapy for localized disease.Ifosfamide, epirubicin and etoposide (IVE) are used in cases of relapse and which are chemosensitive.Another regimen that is used in cases of relapse and chemosensitive cases is etoposide, cytosine, arabinoside, methylprednisolone and cisplatin (ESHAP).In cases of

Discussion
The first case series of extranodal NHL of oral cavity (30 cases) was published in 1972 by Freeman et al. (1972).Hashimoto and Kurihara (1982) and the largest case series of extranodal NHL of oral cavity (71 cases) was by Solomides et al. (2002) (Table 3).In this study 42 cases of extranodal NHL of oral cavity is reported.Van der Waal et al. (2005) published a series (40 cases) of primary extranodal NHL of the oral cavity in which males were most commonly affected.This male predominance was noted in other series (Table 3), however Kemp et al. (2008) found 53% of these tumors in females and is also observed in other series (Table 3).In this study the majority of cases were in males with a male: female ratio of 1.3:1.This ratio is smaller than the 2.4:1 ratio reported by a previous study of lymphoma carried out at the Department of Pathology, University of Malaya, however that study described lymphomas from all over the body (Peh, 2001).The median age is 47 years, with previous case series of oral NHL reporting a mean of 59 (van der Waal et al., 2005) and 42.6 years (Shah et al., 2011).
In Malaysia, the NHL occurs more commonly in Chinese (22.51-79%) followed by those of Malay (5-16.37%)and lastly Indians (2.5-16%) (Peh, 2001;Peh et al., 2004).However, in this study, there was equal distribution between Malay and Chinese (43.9%).The occurance of NHL in Indians has been reported to be rare (Shah et al., 2011) which was also reflected in this study (2 cases).
The most common site involved in oral cavity is palate and gingiva (Takahashi et al., 1987;Shah et al., 2011) in this series the palate and gingiva represent about 17.7 and 4.8% of the lesions respectively.It was reported that 15-45% of intra-oral NHL occurs in the jaws, with the mandible being the less frequent site.Larson et al. (1984) studied 100 patients with extra nodal lymphoma of the head and neck and non involved the mandible.Eisnbound et al. (1983;1984) in their study of 31 case of oral NHL found 14 patients with bone involvement, only 5 of them were in the mandible.However, Pazoki et al. (2003) reported 3 mandibular and 1 maxillary intrabony NHLs, and Etemad-Moghadam et al. (2010) found that the mandibular lesion exceed the maxillary.In this study 38.1% of the tumors were intra-bony however the mandible was more affected than the maxilla and other oral cavity sites.
Lymphomas of the salivary glands accounts for Figure 1.A) Photomicrograph of Burkitt's Lymphoma Showing Small Round Cells with Scanty Cytoplasm and Multiple Small Nuclei Interspersed by Macrophages (H and E Stain, Magnification 10X); B) Photomicrograph Showing Ki-67 Labeling Index was 100% (Magnification 10X)