Irshad N. Soomro ( Department of Pathology, The Aga Khan University Hospital, Karachi. )
Samina Noorali ( Department of Pathology, The Aga Khan University Hospital, Karachi. )
Syed Abdul Aziz ( Department of Pathology, The Aga Khan University Hospital, Karachi. )
Suhail Muzaffar ( Department of Pathology, The Aga Khan University Hospital, Karachi. )
Shahid Pervez ( Department of Pathology, The Aga Khan University Hospital, Karachi. )
Akbar S. Hussainy ( Department of Pathology, The Aga Khan University Hospital, Karachi. )
Tariq Moatter ( Department of Pathology, The Aga Khan University Hospital, Karachi. )
Gastric carcinoma with lymphoid stroma is a rare and well known entity. Histologically tumour is extremely cellular infiltrated by fairly large number of lymphocytes. The infiltrate can be so dense that a mistaken diagnosis of lymphoma may be made on endoscopic biopsy or even in resection specimen. The entity is known by various names, which include medullary carcinoma with lymphocytic infiltration of the stomach, blue cell cancer, lymphoepithelial carcinoma of stomach or gastric carcinoma with lymphoid stroma1.
Association of this type of gastric carcinoma with Epstein Barr Virus is well known2. In a study from Japan, EBV sequence was detected in 81 out of 99 cases. Whereas only 21 out of 42 ordinary adenocarcinoma showed this sequence3. We describe a case of gastric carcinoma with lymphoid stroma in a female. We were able to detect Epstein Barr Virus DNAby polymerase chain reaction in this case.
A 55 years old female presented with signs and symptoms of gastric outlet obstruction. This was due to a pyloric growth for which a complete gastrectomy was performed. The specimen received was a stomach which on opening revealed an ulcerated tumour measuring 5 x 3 cms involving full thickness of the wall. Tumour was close to one of the excision margins i.e., within 0.2 cm. Sections were taken from the lesion. These 5 mm sections were stained with hematoxylin and eosin.
Histology revealed an infiltrative lesion formed predominately by lymphoid cells. Between these cells there was a scattered population of round to oval cells with scanty cytoplasm. In some areas there was a nesting pattern. Mitotic activity was variable. The stroma was nondesmoplastic. Tumour involved full thickness of the wall and three out of six recovered lymph nodes showed evidence of metastasis.
The differential diagnosis of this tumour was a gastric carcinoma with lymphoid stroma and a non-Hodgkin’s lymphoma. Immunohistochem istry using peroxidase antiperoxidase method was attempted. There was a dense mixed population of B and T lymphocytes. Majority of these were of T-phenotype, although lymphoid follicles contained B cells.
However, there were a number of tumour cells morphologically similar to lymphoid cells, which were reactive for both cytokeratin antibodies. Mucin stains PAS and alcian blue were equivocal. On the basis of cytokeratin positivity a diagnosis of gastric carcinoma with lymphoid stroma was made. In view of well known association of this tumour with Epstein Barr Virus, we explored this lesion further using polymerase chain reaction method.
Paraffin embedded tissue sections of 5 mm were deparffinized and dried. DNA was extracted by Nucleon DNA Extraction Kit (Nucleon Biosciences, USA). PCR assay was carried out according to the method described4. Primer pairs specific for gp220 region of EBV genome were synthesized by using an Applied Biosystems DNA synthesizer.
The PCR was- performechin a Perkin Elmer 9600 thermocyler. DNA was added to the PCR mixture which contained, reaction buffer (10mM Tris pH 7.4, 50mM KC1 and 1.5 mM MgCI), 200 mM each of dNTPs, 0.5 U Taq polymerase, 200 ng of each primer in a final volume of 100 ml. After initial denaturation at 94°C, 45 cycles of amplification were performed at 94°C for 1.30 min, 53°C for 1.30 min and extension at 72°C for 1.30 min. The amplified product was subjected to electrophoresis on a 2% agarose gel and visualized by ethidium bromide staining. An amplified product of 239 bp was suggestive of EBV DNA. Both positive and negative controls were,used with each assay.
Immunocytochemistry was done by three step peroxidase antiperoxidase method. Primary antibody was laid for 90 minutes, followed by secondary antibody and PAP complex for 45 minutes each. Color was developed by diaminobenzidine. Monoclonal antibodies used included cytokeratin CAM 5.2, AE1/AE3 and lymphoid markers LCA (CD45), Pan B (L26) and Pan T (UCHLI).
Gastric carcinoma with lymphoid stroma is a relatively rare entity. In a series of 867 cases only 27 cases were found1. In another study of 8457 gastric carcinoma there were 132 cases3. Watanabe H5 et al described 49 cases in a series of 1041 cases. Significantly favourable prognosis of gastric carcinoma with lymphoid stroma in comparison to ordinary carcinoma requires accurate classification and may not be possible without immunocytochemistry in some cases3. It is thought that infiltrating lymphocytes play a role in immune surveillance against invading tumour cells and hence long term survival. In this case though EBV DNA was detected by polymerase chain reaction, but are being carried out to determine the location of EBV DNA by in-situ hybridization.
The Epstein Barr Virus is associated with a variety of lymphoproliferative disorders such as Burkitt’s lymphoma, Hodgkin disease, T cell lymphoma alongwith epithelial malignancies including nasopharyngeal carcinoma, lymphoepithelioma as carcinoma of the salivary glands, lung and thymus. Both ordinary gastric adenocarcinomas and carcinomas with lymphoid stroma are known to have EBV sequences. However, this association remains significant in the latter category in stomach. Oda et al6showed EBV DNA and RNA within the nuclei of carcinoma cells by in-situ hybridization and polymerase chain reaction respectively. Infiltrating lymphocytes and normal epithelium adjacent to tumour were EBV negative. Southern Blot analysis indicated clonal proliferation of tumour cells and episomal form of EBV. The conclusion was that EBV infection occurs before transformation and may be related to oncogenesis of EBV associated gastric carcinoma.
The mechanism of an abundant lymphocytic infiltration in GCLS could be a direct response either to the virus or to the virally induced antigens expressed in the neoplastic cells7. Immunohistochemical studies as in our case have confirmed presence of both T-cell and B-cell populations as shown by Minamoto et al1. T-ceIl distribution was even throughout the tumour particularly adjacent to carcinoma cell nests. B-cells however, were sparsely scattered in the tumour. However, the main cellular component of lymphoid follicles were B-cells.
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2. Burke AP, Yen TSB, Shekitka KM, et al. Lymphoepithelial carcinoma of the stomach with Epstein Barr Virus demonstrated by Polymerase chain reaction. Mod, Pathol., 1990;3:377-80.
3. Nakamura S, Ueki 1, Yao 1, et at. Epstein-Barr Virus in gastric carcinoma with lymphoid stroma. Cancer, 1994;73:2239-49.
4. Telenti A. PCR detection and typing of Epstein-Barr virus. Editors: Pershing DH, Smith TF, Tenover FC, et al. Diagnostic Molecular Microbiology. Principles and applications. Washington, DC. USA, American Society for Microbiology, 1993, pp. 344-49.
5. Watanabe H, Enjoji M, lmai T. Gastric carcinoma with lymphoid stroma. Cancer, 1976;38:232-43.
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