Journal of Cancer Research and Therapeutics Medknow Publications on behalf of the Association of Radiation Oncologists of India (AROI) ISSN: 0973-1482 EISSN: 1998-4138 Vol. 6, Num. 4, 2010, pp. 549-551

Journal of Cancer Research and Therapeutics, Vol. 6, No. 4, October-December, 2010, pp. 549-551

Case Report

A rare case of primary gastric plasmacytoma: An unforeseen surprise

Navin Krishnamoorthy¹, Munita M Bal¹, Mukta Ramadwar¹, Kedar Deodhar¹, KM Mohandas²

¹ Department of Pathology, Tata Memorial Hospital, Parel, Mumbai - 400 012, India
² Department of Digestive diseases, Tata Memorial Hospital, Parel, Mumbai - 400 012, India

Correspondence Address: Munita M Bal, Department of Pathology, Tata Memorial Hospital, Parel, Mumbai - 400 012, India, munita.m@rediffmail.com

Code Number: cr10135

PMID: 21358099

DOI: 10.4103/0973-1482.77067

Abstract

Keywords: Differential diagnosis, immunohistochemistry, primary gastric plasmacytoma

Introduction

Extramedullary plasmacytoma (EMP) is a plasma cell neoplasm that presents as a solitary lesion in the soft tissues, without systemic involvement. EMPs are rare tumors that form 3-4% of all plasma cell neoplasms. ^[1] A majority of the EMPs are observed in the upper aerodigestive passages. ^[1] Primary gastric plasmacytoma (PGP) is an extremely rare form of EMP, with only approximately 100 cases since 1928. ^[2] Most cases have been reported in the Western or Japanese literature and reports from India are particularly scarce. ^[2]

Herein, we report a very rare case of PGP that clinically simulated a carcinoma.

Case Report

A 57-year-old Indian gentleman, with past good health, presented with malaena and loss of appetite. Examination was unremarkable except for a moderate pallor. Complete blood counts revealed hemoglobin of 80 g/L. Routine biochemistry was within normal limits. Computed tomography scan revealed a well-defined, rounded lesion, measuring 4.1 × 2.4 cm, arising from the greater curvature of stomach and projecting intraluminally. On endoscopy, a nodular lesion with central umblication was noted in the greater curvature. With a clinical diagnosis of carcinoma stomach, a gastrectomy was performed. Thereafter, he was referred to our tertiary-care centre for histopathological review and further management.

Gross examination revealed a 4.5 × 3.5 × 2.5 cm protuberant, centrally umblicated mass on the greater curvature of stomach. Mucosa was flattened and on slicing, a grayish-white, firm, nodular tumor was seen within the muscularis propria, sparing the serosa.

Microscopy revealed nodular deposits of mature-looking plasma cells within the muscularis propria [Figure - 1]. The cells possessed eccentrically placed nuclei with cart-wheel chromatin, inconspicuous nucleoli, and showed frequent binucleation/mutinucleation and mild anaplasia without blastic morphology [Figure - 2]. A few giant cells were also present. No admixture with lymphoid cells or presence of centrocyte-like cells, lymphoid follicles, or lymphoepithelial lesions (LELs) was seen in any of the section. Overlying mucosa was unremarkable. No features of chronic gastritis or H. pylori were seen in the mucosa.

On immunohistochemistry [Figure - 3], the tumor cells were positive for leukocyte common antigen (CD45), syndecan-1 (CD 138), and lambda light chain, but were negative for CD20, CD3, kappa, and CD30. Mib-1 labeling index was 2%.

A diagnosis of plasmacytoma was made, subsequent to which the patient was investigated for multiple myeloma. Bone marrow aspiration and biopsy did not show plasma cell infiltration. Further staging including serum electrophoresis and immunofixation, beta-2 microglobulin, skeletal survey and MRI of the spinal cord and pelvis were found to be normal. Urine for Bence Jones protein was negative. According to all the findings, the criteria of PGP were fulfilled.

Discussion

Plasma cell neoplasms are categorized into four groups; multiple myeloma (MM), plasma cell leukemias, solitary plasmacytomas of the bone (SPB), and EMP. ^[2] The diagnosis of EMP requires demonstration of a histologically confirmed single lesion comprising monoclonal plasma cell infiltration, a negative skeletal survey, and no evidence of tumor in the bone marrow.

Eighty to 90% of EMPs arise in the upper aerodigestive tract. ^[1] Among the EMPs, gastrointestinal involvement is very rare, representing less than 5% of all EMPs. ^[2] In a review involving a detailed literature search analyzing 869 EMPs, stomach as a primary site formed a mere 2% of all EMPs. ^[2] All the segments of the gastrointestinal tract may be involved by EMP, with the small intestine being the most common, followed by stomach, colon, and esophagus.

Most patients of gastric plasmacytomas (GPs) are elderly with nonspecific symptoms, including anorexia, weight loss, epigastric discomfort, or gastrointestinal bleeding. On endoscopy, GPs commonly present as a nodular mass wherein a diagnosis of GIST or lymphoma is usually suggested. Not infrequently, the findings on endoscopy simulate a carcinoma when the mass is ulcerated or a linitis plastica when mucosal folds are diffusely thickened. ^[3]

Differential diagnoses of GP include non-Hodgkin′s lymphomas that may show plasmacytic differentiation such as lymphoplasmacytic lymphoma, follicular lymphoma, monocytoid B-cell lymphoma and, particularly, mucosa-associated lymphoid tissue (MALT) lymphomas. In these lymphomas, neoplastic cells are CD20+CD138-ve and admixed with variable numbers of plasma cells unlike a plasmacytoma which contains an exclusive population of neoplastic plasma cells (CD20 negative). Additionally, centrocyte-like CD20-positive cells, lymphoid follicles, and LELs differentiate gastric MALT from a GP. Other differential diagnoses include a plasma cell granuloma and plasma cell variant of Castleman′s disease. The former shows admixture of polyclonal plasma cells with other inflammatory cells, while anemia, fever, hypergammaglobulinemia, multifocality, and hyperplastic germinal centers in gastrectomy specimen are hallmarks of the latter. Awareness of these mimics is extremely crucial, especially, while interpreting a small biopsy, since the diagnosis of a GP, is almost never suspected clinically.

When primarily presented, a GP may be the first indication of multiple myeloma (MM) which needs to be excluded through appropriate testing. Treatment of EMP is not standardized. Analysis of the published data indicates that surgical treatment or irradiation, with or without chemotherapy, has been the predominant therapeutic approach. ^[2] There is no published evidence that adjuvant chemotherapy is beneficial. ^[4] Interestingly, some reports have documented a complete regression after helicobacter pylori treatment, while others have shown improvement in abnormal endoscopic findings without histologic benefit. ^[5] These findings remain to be validated and a potential association of a GP and H. pylori is still not established. ^[6]

To date, there are no long-term follow-up studies of GPs. The course of EMP is favorable with a 70% disease-free survival at 10 years. ^[7] The rate of progression of EMP to multiple myeloma ranges from 11% to 30%, at 10 years. ^[8]

Finally, this case illustrates the importance of awareness of this rare entity, both for the pathologist as and the treating clinician when considering differential diagnoses of gastric tumors. Also, the role of immunohistochemistry for establishing monoclonality and segregating this entity from potential mimics, especially in a small biopsy is emphasized. A diagnosis of PGP entails detailed work-up for multiple myeloma and a strict oncologic surveillance.

References

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