Carcinoma-like signet-ring cells in gastric mucosa-associated lymphoid tissue (MALT) lymphoma

Signet-ring cells in pleural and peritoneal effusions identified on Wright stains – A diagnostic pitfall

Objectives:

Signet-ring cells (SRCs) in effusion specimens represent a diagnostic challenge. In this study, a consecutive series of pleural and peritoneal effusions with benign SRCs are examined and compared with malignant SRCs.

Material and Methods:

We reviewed consecutive Wright-stained serous effusion slides and searched for cases with SRCs. Corresponding ThinPrep slides and clinical histories were reviewed. Cytology cases with known signet-ring adenocarcinoma were retrieved and reviewed.

Results:

Four hundred Wright-stained serous effusions were reviewed. Eighteen cases were identified with SRC-like cells. Thirteen patients had liver cirrhosis, three patients had end-stage renal disease, one patient had a history of pancreatic adenocarcinoma, and one patient had endometrioid carcinoma. For the latter two patients, the primary tumor showed no histologic findings of signet-ring features. In all cases, no SRCs were found on the corresponding ThinPrep slides. Five cytology cases with malignant SRCs were reviewed. Benign SRCs have a uniformly pale and markedly distended cytoplasm, and the nuclei are thin and curved. The malignant SRCs showed larger non-curved nuclei and bubbly mucin-containing cytoplasm.

Conclusion:

Mesothelial cells and histiocytes can mimic signet-ring adenocarcinoma cells on Wright-stained slides. Correlation with ThinPrep specimens is necessary before reporting, as the SRCs typically are not present in ThinPrep preparations.

The broad landscape of follicular lymphoma: Part I

Follicular lymphoma is a neoplasm derived from follicle center B cells, typically both centrocytes and centroblasts, in variable proportions according to the lymphoma grading. The pattern of growth may be entirely follicular, follicular and diffuse, and rarely completely diffuse. It represents the second most common non-Hodgkin lymphoma, after diffuse large B-cell lymphoma and is the most common low-grade mature B-cell lymphoma in western countries. In the majority of cases, follicular lymphoma is a nodal tumor, occurring in adults and frequently associated with the translocation t(14;18)(q32;q21)/IGH-BCL2. However, in recent years the spectrum of follicular lymphoma has expanded and small subsets of follicular lymphoma, which differ from common follicular lymphoma, have been identified and included in the current 2017 WHO classification. The aim of our review is to describe the broad spectrum of follicular lymphoma, pointing out that the identification of distinct clinicopathological variants of follicular lymphoma is relevant for patient outcomes and choice of treatment.

Marginal zone B-cell lymphoma: lessons from Western and Eastern diagnostic approaches

Marginal zone B-cell lymphomas (MZLs) are a group of clinically indolent B-cell lymphomas postulated to derive from memory B lymphocytes in the 'marginal zone' of secondary lymphoid tissue. Today, MZL is recognised as a nosological umbrella term encompassing distinct entities with some shared phenotypic and genotypic features, including extranodal marginal zone B-cell lymphoma (EMZL) or mucosa-associated lymphoid tissue (MALT) lymphoma, splenic MZL, and nodal MZL, accounting for approximately 70%, 20%, and 10% of MZLs, respectively. These lymphomas share some phenotypic and genotypic features and have some variants and related provisional diseases, but are different in regards to their clinical and molecular characteristics. In addition, they are frequently associated with chronic antigenic stimulation represented either by infectious agents, particularly bacteria and viruses, or autoimmune diseases as exemplified by Sjögren syndrome, Hashimoto thyroiditis, and newly recognised IgG4-related disease. Furthermore, several chromosomal translocations have been identified in EMZL. In this review, we will focus on the updated histopathological criteria and the main problems with differential diagnoses in order to aid the diagnostic approach in our routine practice.

Primary signet ring cell carcinoma of the pancreas: Cytopathology review of a rare entity

Primary signet ring cell carcinoma of the pancreas (PSRCCP) is an extremely rare diagnosis that has not been extensively studied in literature. Primary and metastatic neoplasms to the pancreas may exhibit cytomorphological similarities to signet ring cells, posing diagnostic challenges. In this article, we review PSRCCP and provide a study of several primary pancreatic neoplasms that may mimic the appearance of PSRCCP upon cytopathology evaluation, shedding light on the existence of this dilemma, and helping cytopathologists in navigating similar scenarios in their practice.

Consensus on the pathological definition and classification of poorly cohesive gastric carcinoma

BACKGROUND AND AIMS

Clinicopathological characteristics of gastric cancer (GC) are changing, especially in the West with a decreasing incidence of distal, intestinal-type tumours and the corresponding increasing proportion of tumours with Laurén diffuse or WHO poorly cohesive (PC) including signet ring cell (SRC) histology. To accurately assess the behaviour and the prognosis of these GC subtypes, the standardization of pathological definitions is needed.

METHODS

A multidisciplinary expert team belonging to the European Chapter of International Gastric Cancer Association (IGCA) identified 11 topics on pathological classifications used for PC and SRC GC. The topics were debated during a dedicated Workshop held in Verona in March 2017. Then, through a Delphi method, consensus statements for each topic were elaborated.

RESULTS

A consensus was reached on the need to classify gastric carcinoma according to the most recent edition of the WHO classification which is currently WHO 2010. Moreover, to standardize the definition of SRC carcinomas, the proposal that only WHO PC carcinomas with more than 90% poorly cohesive cells having signet ring cell morphology have to be classified as SRC carcinomas was made. All other PC non-SRC types have to be further subdivided into PC carcinomas with SRC component (< 90% but > 10% SRCs) and PC carcinomas not otherwise specified (< 10% SRCs).

CONCLUSION

The reported statements clarify some debated topics on pathological classifications used for PC and SRC GC. As such, this consensus classification would allow the generation of evidence on biological and prognostic differences between these GC subtypes.

Pathological features of total gastrectomy specimens from asymptomatic hereditary diffuse gastric cancer patients and implications for clinical management

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant syndrome characterised by multigenerational diffuse gastric cancer, and is mainly caused by germline alterations in the CDH1 gene. Currently, endoscopy has limited diagnostic accuracy, and total gastrectomy (TG) is the treatment of choice for asymptomatic CDH1 carriers. In this study, we aimed to obtain a better understanding of HDGC syndrome by exploring the histopathological findings of TG specimens from asymptomatic HDGC patients. A comprehensive literature review was carried out, searching for TGs performed in asymptomatic HDGC patients. Fourteen unpublished cases, analysed in our institution, were also included. The series encompassed 174 CDH1 carriers. Preoperative endoscopic biopsies were positive in 28.3%. A macroscopic lesion was apparent in 11.7% of TGs. Histopathological analysis revealed intraepithelial lesions and/or intramucosal signet ring cell carcinoma in 87.9% of TGs. When we explored the type of protocol used for handling the specimens, we found that microscopic cancer foci were detected in 95.3% of TGs when a total-embedding protocol (assessment of the totality of gastric mucosa) was applied, and only in 62.5% when no specific protocol was used (P < 0.001). Helicobacter pylori infection was found in 23.4% cases. In conclusion, a thorough histopathological examination of gastric mucosa remains the gold standard for detection of cancer foci in HDGC gastrectomy specimens, requiring experienced pathologists for an accurate diagnosis. A better understanding of the natural history of HDGC will enable better clinical management of HDGC patients, particularly regarding the optimal timing for the performance of TG.

Identification of Signet Ring Cell Change in Colonic Subserosa in the Setting of Clostridium difficile Colitis

Signet ring cell change of intestinal epithelial cells is a rare but well-known mimicker of signet ring cell carcinoma and is often associated with ischemic and/or pseudomembranous colitis. Instead, signet ring cell change involving nonepithelial cells in the subserosa of the intestine is an extremely rare finding with only a single case report in the literature to date. We report a new case of benign signet ring cell change localized in the subserosa of the large bowel incidentally identified in a resection specimen for Clostridium difficile colitis mimicking a metastatic signet ring cell carcinoma. Based on the morphologic features and immunohistochemical profile, we propose that these signet ring cells may possibly represent modified/degenerated fat cells. Furthermore, we discuss how to differentiate benign signet ring cells from a signet ring cell carcinoma.

A rare presentation of gastric signet ring cells: signet ring cell lymphoma

We herewith present a rare and interesting case of gastric signet ring cell lymphoma (SRCL) in a 40-year-old retroviral positive lady. SRCL is a rare morphological variant of nodal lymphomas.Biopsy from the suspected lesion in the stomach showed diffuse sheets of cells with a large central vacuole displacing the nucleus to the periphery of the cell, imparting signet ring cell morphology. Negative reaction to PAS (Periodic acid Schiff) stain and subsequent strong positivity for the immunohistochemical markers such as CD45 (Leucocyte commonantigen) and CD20, a B-cell marker helped us to arrive at a diagnosis of signet ring B- cell lymphoma.

Signet ring lymphoma: a potential diagnostic mishap

Signet ring lymphomas are proliferations of malignant lymphoid cells containing cytoplasmic inclusions or vacuoles that displace the nucleus to the side, imparting a "signet ring" appearance. These signet ring cells, particularly those with cytoplasmic vacuoles, may be mistaken for an adenocarcinoma rather than a lymphoma, if sufficient material is not available to differentiate the case by immunohistochemical stains or flow cytometry. The pathologist must also be aware of this entity so that appropriate studies may be untaken.

Extreme Signet Ring Cell Change in a Large B-Cell Lymphoma of Follicular Origin

We report a large B-cell lymphoma of follicular origin with extreme signet ring cell differentiation. Initially classified as follicular lymphoma on a fine needle core biopsy, the presence of cohesive sheets of extrafollicular signet ring cells triggered an excisional biopsy for further characterization. The excised lymph node revealed focal follicular hyperplasia, follicular lymphoma, and a neoplasm composed of vague nodules and sheets of large atypical cells, all of which virtually exhibited large clear intracytoplasmic vacuoles with peripheral displacement of nuclei. The tumor cells were negative for mucin and lacked immunoreactivity with pancytokeratin, but were strongly immunoreactive with CD20, BCL-2, BCL-6, and CD10 antibodies. Electron microscopy studies revealed electron-lucent vacuoles with no particular internal structure. This case is unique in that extreme signet ring cell differentiation somewhat obscured the true cytological identity of the interfollicular lymphoma and suggested alternative diagnoses.

Nonneoplastic signet-ring cell change in gastrointestinal and biliary tracts: a pitfall for overdiagnosis

Nonneoplastic signet-ring cell change (SRCC) is a rare but known phenomenon in gastrointestinal and biliary tracts and is always associated with underlying mucosal ulceration/erosion secondary to infection, ischemia, or other etiology. Because nonneoplastic SRCC closely mimics signet-ring cell adenocarcinoma (SRCA), differentiation of these 2 entities is critical because misdiagnosis of nonneoplastic SRCC as SRCA can lead to intense therapeutic interventions such as surgery and/or chemoradiation therapy. In this review, a brief overview on nonneoplastic SRCC in gastrointestinal and biliary tracts, including the spectrum of clinical presentation, important histologic features, and immunohistochemical markers that are useful in differentiating nonneoplastic SRCC from SRCA, is provided. The pathogenesis of nonneoplastic SRCC in gastrointestinal and biliary tracts is discussed.

An unusual uterine tumor with signet ring cell features

In 2004, a 56-year-old woman was diagnosed with Stage IA follicular lymphoma in a cervical lymph node biopsy. The patient experienced total remission after local radiation therapy. In 2009, a control computed tomography scan evidenced a pelvic mass, prompting total hysterectomy. The latter harbored a 4.8-cm intramural uterine tumor corresponding to a mostly diffuse and focally nodular proliferation of medium to large cells, with extensive, periodic acid-Schiff negative, signet ring cell changes, and a pan-keratin negative, CD20+, CD10+, Bcl2+, Bcl6+ immunophenotype. Molecular genetic studies showed the same clonal IGH gene rearrangement in the lymph node and the uterus, establishing the uterine tumor as a relapse of the preceding follicular lymphoma, although no signet ring cells were evidenced at presentation. Uterine localization of lymphomas is rare, and lymphomas with signet ring cell features are uncommon. This exceptional case exemplifies a diagnostically challenging situation and expands the differential diagnosis of uterine neoplasms displaying signet ring cell morphology.

Unusual presentation of localized gastric mucosa-associated lymphoid tissue lymphoma mimicking poorly differentiated gastric adenocarcinoma

The risk of misdiagnosing neoplastic cells typically infiltrating an epithelium forming a lymphoepithelial lesion as poorly differentiated gastric cancer in endoscopic biopsies, particularly in low-grade mucosa-associated lymphoid tissue (MALT) lymphomas, is described. A 76-year-old woman was referred for management of a poorly differentiated gastric adenocarcinoma. Diagnostic endoscopy in our unit showed a 2 cm raised, submucosal lesion with central erosion in the upper body of the stomach, but repeat biopsies of the lesion were interpreted as inflamed gastric mucosa and negative for malignancy. Systematic gastric biopsies to rule out any foci of MALT lymphoma changes were also negative. Therefore, endoscopic submucosal dissection was performed to obtain an accurate specimen. Histology revealed centrocyte-like cells and a lymphoepithelial lesion invading into the mucosa with obliteration of the gastric glands, which was initially interpreted as poorly differentiated adenocarcinoma.

Lymphoproliferative disorders of the gastrointestinal tract: a review and pragmatic guide to diagnosis

CONTEXT

The gastrointestinal tract is the most common site of extranodal lymphomas. Although all histologic categories of malignant lymphoma develop in the gastrointestinal tract, large B-cell lymphomas predominate, followed by extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue (MALT) type; the latter is especially prevalent in stomach. The acceptance of extranodal marginal zone lymphoma of MALT type as a clinicopathologic entity has reduced the number of cases that formerly were interpreted as florid lymphoid hyperplasia ("pseudolymphoma"). Nonetheless, the distinction of lymphoid hyperplasia from a lymphoma of MALT type in small biopsy specimens remains problematic.

OBJECTIVE

To assess the relevant morphologic, immunologic, molecular, and genetic properties of gastrointestinal lymphomas and to present a feasible tactic for diagnosis, expressly for small biopsy specimens.

DATA SOURCES

Case-derived material and literature review using PubMed (National Library of Medicine).

CONCLUSIONS

Most gastrointestinal lymphomas are readily amenable to an unqualified diagnosis, primarily those cases consisting of monomorphic large cells whether of B- or T-cell lineage, including cases associated with enteropathy. Diagnosis for infiltrates dominated by small lymphocytes remains taxing, as the differential diagnosis embraces not only MALT lymphoma and lymphoid hyperplasia but also mantle cell lymphoma, follicular lymphoma, and chronic lymphocytic leukemia/small lymphocytic lymphoma. Adherence to strict morphologic criteria is the standard for diagnosis, but these criteria should be augmented by immunologic studies together with judicious use of molecular techniques to determine clonality. In establishing a diagnosis of gastric marginal zone lymphoma of MALT type, determination of t(11;18)(q21;q21) status may be required since this translocation has clinical ramifications.

Hereditary diffuse gastric cancer: updated consensus guidelines for clinical management and directions for future research

25–30% of families fulfilling the criteria for hereditary diffuse gastric cancer have germline mutations of the CDH1 (E-cadherin) gene. In light of new data and advancement of technologies, a multidisciplinary workshop was convened to discuss genetic testing, surgery, endoscopy and pathology reporting. The updated recommendations include broadening of CDH1 testing criteria such that: histological confirmation of diffuse gastric criteria is only required for one family member; inclusion of individuals with diffuse gastric cancer before the age of 40 years without a family history; and inclusion of individuals and families with diagnoses of both diffuse gastric cancer (including one before the age of 50 years) and lobular breast cancer. Testing is considered appropriate from the age of consent following counselling and discussion with a multidisciplinary team. In addition to direct sequencing, large genomic rearrangements should be sought. Annual mammography and breast MRI from the age of 35 years is recommended for women due to the increased risk for lobular breast cancer. In mutation positive individuals prophylactic total gastrectomy at a centre of excellence should be strongly considered. Protocolised endoscopic surveillance in centres with endoscopists and pathologists experienced with these patients is recommended for: those opting not to have gastrectomy, those with mutations of undetermined significance, and in those families for whom no germline mutation is yet identified. The systematic histological study of prophylactic gastrectomies almost universally shows pre-invasive lesions including in situ signet ring carcinoma with pagetoid spread of signet ring cells. Expert histopathological confirmation of these early lesions is recommended.

Pseudoneoplasms of the gastrointestinal tract

CONTEXT

The pathologist plays the leading role in distinguishing pseudoneoplasms from truly neoplastic lesions in the gastrointestinal tract.

OBJECTIVE

This review was conducted to heighten awareness of pseudoneoplasms, to help differentiate among the various types of pseudoneoplasms, and to help distinguish pseudoneoplasms from malignancies.

DATA SOURCES

This review is based on the medical literature on pseudoneoplasms in MEDLINE and the authors' own experiences. Reference lists of retrieved articles were also reviewed to identify additional articles.

CONCLUSIONS

A classification of pseudoneoplasms, according to the mechanism of injury to the gastrointestinal tract, morphologic patterns, and heterotopia, may be useful in providing a diagnostic framework in which ancillary techniques often have a diagnostic role. Several pseudoneoplasms may be closely associated with true neoplasms (eg, malakoplakia, prolapsetype lesions) because of the nonspecific nature of the response of the intestine to injury.

Synchronous and metachronous occurrence of gastric adenocarcinoma and gastric lymphoma: A review of the literature

The occurrence of both primary gastric lymphoma and gastric adenocarcinoma in the same patient is a rare entity. The possible causative factors of synchronous or metachronous occurrence of both malignancies and varieties in the treatment modalities are reviewed according to published cases in English language medical literature.

Infectious agents in mucosa-associated lymphoid tissue-type lymphomas: pathogenic role and therapeutic perspectives

Mucosa-associated lymphoid tissue (MALT) lymphoma probably constitutes the best in vivo model showing how complex interplay between B lymphocytes and the surrounding microenvironment may lead to a neoplastic disorder. After the seminal discovery of the pathogenic association between Helicobacter pylori and gastric MALT lymphomas, evidence suggests the possible involvement of other infectious agents in the development of MALT lymphomas arising at different body sites. Although several other bacteria (Borrelia burgdorferi, Campylobacter jejuni, and Chlamydia psittaci) and viruses (Hepatitis C virus) seem to play a role in lymphomas presenting at different locations, a possible common pathogenic mechanism is emerging. Several lines of evidence suggest that different infectious agents might provide a chronic antigenic stimulation that elicits host immune responses able to promote clonal B-cell expansion. This model is also substantiated by the increasing number of patients with MALT lymphomas who exhibit objective clinical responses after antimicrobial therapy. A multidisciplinary approach is critical to better understand the complex etiopathogenesis of MALT lymphomas with the final goal to dissect the clinicopathologic heterogeneity of these disorders and design more tailored preventive and therapeutic approaches.

Signet-ring cell change versus signet-ring cell carcinoma: a comparative analysis

Signet-ring cell change (SCC) is a nonneoplastic condition that morphologically simulates signet-ring cell carcinoma (SRCA). The few case reports on SCC have focused on morphologic characteristics in distinguishing benign from malignant. In biopsy specimens, however, SCC can be easily confused with SRCA, which often demonstrates innocuous cytologic features. The object of this study is twofold: 1) to report 14 additional cases of SCC, comparing their morphologic and phenotypic features with that of SRCA; and 2) to evaluate the incidence of SCC in pseudomembranous colitis. Paraffin sections of biopsy or resection specimens containing focal or extensive SCC and 5 cases of colonic SRCA were stained with hematoxylin and eosin, periodic-acid Schiff stain with and without diastase digestion, and by standard ABC immunoperoxidase procedure using antibodies to E-cadherin, p53, and Ki-67. Both cells in SCC and SRCA were strongly positive for neutral mucins. Cells in SCC were strongly positive for E-cadherin and negative for p53 and Ki-67. In contrast, cells in SRCA were strongly positive for p53, exhibited high proliferation, and demonstrated absent or weak positivity for E-cadherin. Although SCC is not well recognized in pseudomembranous colitis, the incidence is fairly high: 14 of 50 (28%) cases showed variable numbers of signet-ring cells. Extensive SCC, although rare, can occur in different clinical conditions and can be easily mistaken for SRCA. When in doubt, routine immunohistochemical stains such as p53, Ki-67, and E-cadherin can help to differentiate SCC from SRCA.

Atypical histiocytic infiltration simulating diffuse-type carcinoma in a gastric ulcer due to non-steroidal anti-inflammatory drugs

A 83-year old man treated with naproxen during two years was admitted because of hypovolemia and peritoneal irritation. A panendoscopic study was performed and an ulcer localized at the large curvature of the stomach was disclosed. In the gastrectomy specimen the ulcer showed necrosis, edema, fibrosis, chronic inflammatory infiltrate with lymphocytes and plasma cells. Additionally, atypical cells with irregular and hyperchromatic nuclei or vacuolated cytoplasm were seen in the lamina propia and infiltrating the muscular layers; isolated signet-ring-like cells were also seen. Histochemical study with periodic acid-Schiff, mucicarmin, and colloidal stains revealed mucosubstances in these cells. A poorly differentiated carcinoma was initially diagnosed. However, the immunohistochemical study were positive for histiocytic markers (CD-68, S-100 protein) and negative for epithelial markers (cytokeratin; and epithelial membrane antigen). The positivity of mucus stains in the histiocytes could be explained in this case by phagocytosis of mucous substances released from broken hyperplastic glands in the vicinity of the ulcer. To our knowledge, atypical histiocytic infiltration in gastric ulcers has not been previously described; thus, it should be included in the group of gastric carcinoma mimicks.

Peculiar artifacts mimicking carcinoma

Artifacts that mimic malignancy may lead to diagnostic difficulty and can cause serious consequences. We present 2 cases received in consultation which demonstrated peculiar artifacts that closely mimicked carcinoma. In case 1, contaminating products of conception were confused with squamous cell carcinoma. In case 2, artifactual signet ring cells induced by procedural trauma were suspicious for signet ring cell carcinoma. In both cases, clinical correlation failed to completely exclude carcinoma, and limited tissue prevented use of ancillary studies. Our final resolution of these artifacts required lengthy and detailed morphologic analysis.

Nonneoplastic endometrial signet-ring cells. Vacuolated decidual cells and stromal histiocytes mimicking adenocarcinoma

We describe 5 patients (mean age, 50 years; all had uterine bleeding) whose routine endometrial biopsy and curettage specimens contained prominent signet-ring cells. Each specimen contained loose aggregates of signet-ring cells scattered within the endometrial stroma that were characterized by peripherally displaced, small, uniform nuclei with indistinct nucleoli and showed no mitotic activity. The central portion of the cytoplasm was occupied by single or multiple cytoplasmic vacuoles. In all cases, the signet-ring cells were reactive for vimentin and negative for epithelial membrane antigen and cytokeratin. Four cases were focally positive for muscle-specific actin or smooth muscle actin and negative for CD68, Mac387, periodic acid-Schiff, mucicarmine, and alcian blue. In these 4 cases, the surrounding endometrial stroma showed decidual changes, and the signet-ring cells demonstrated a morphologic continuum with more typical decidualized stroma. As such, the signet-ring cells in these cases were vacuolated, decidualized endometrial stromal cells. In the remaining case, the vacuolar contents of the signet-ring cells were periodic acid-Schiff-positive and resistant to diastase predigestion, and the cells reacted with Mac387 and CD68. The surrounding stroma showed no decidual reaction. Thus, the signet-ring cells in this case were of histiocytic differentiation. Endometrial stroma occasionally may contain nonneoplastic signet-ring cells that closely mimic adenocarcinoma. At least 2 directions of differentiation, decidual and histiocytic, are possible.

Multiple organ mucosa-associated lymphoid tissue lymphomas often involve the intestine

BACKGROUND

Low grade mucosa-associated lymphoid tissue (MALT) lymphomas usually are confined to single extranodal organs. Although some case reports have been published, clinicopathologic characteristics of multiorgan MALT lymphomas remain unclear.

METHODS

The authors evaluated 7 MALT lymphoma cases involving multiorgans in the past 7 years. In this period, they experienced 304 cases of MALT lymphomas. They analyzed the clinicopathologic features of these cases, including examination of clonal comparison among the lesions.

RESULTS

The patients, 4 females and 3 males, were aged 55-68 years old (average, 60.1 years). Four cases showed multiple organ involvement at the initial diagnosis or after a short period. In the other three cases, primary foci were the stomach, thyroid gland, and ocular adnexa; after a rather long period (3 years or more), distant metastases were found. Although intestinal primary lymphomas are rather rare, six of the seven cases showed large intestinal involvement. Lymph node involvement was proven in only three cases. The patients were rather resistant to the various therapeutic approaches. Although six patients are alive, five are with disease. DNA analyses revealed that in five of the cases evaluated, identical clones were detected among the different affected organs.

CONCLUSIONS

Multiorgan MALT lymphomas are rather rare. Most cases probably derived from a single clone, and lymphoma cells may selectively move among MALTs via a homing system with preferential involvement of the colon. Because multiorgan MALT lymphomas rarely achieve complete remission by treatment with combination chemotherapy or irradiation, MALT lymphomatous lesions should be checked carefully, especially in the large intestine.

When can complete regression of low-grade gastric lymphoma of mucosa-associated lymphoid tissue be predicted after helicobacter pylori eradication?

AIMS

Recent studies suggest that primary low-grade gastric lymphomas of mucosa-associated lymphoid tissue (MALT) are cured in many cases between 1 and 18 months after H. pylori eradication. The aim of this study is to elucidate when complete regression (CR) of MALT lymphoma can be histologically predicted after H. pylori eradication.

METHODS AND RESULTS

Twenty-one patients with low-grade gastric MALT lymphoma were treated with triple therapy (amoxicillin, clarythromycin and proton pump inhibitor) for 14 days. Subsequently, they were followed up by sequential endoscopy and biopsy (number of biopsy specimens for each endoscopy is 3-8, with an average of 4) from 91 to 657 days (average: 309 +/- 165 days). Eradication of H. pylori infection was achieved in all patients. Nine patients were free of lymphoma at 1 to 2 months after eradication and remained in CR at 163-657 days. Twelve patients showed residual lymphoma at 1 to 2 months after eradication. Five out of 12 patients revealed only one or two small foci of lymphoma-cell aggregation and showed a high incidence (80%) of CR at the latest biopsy (135-434 days, average 276 +/- 115 days after eradication), while seven patients showed diffuse remains of lymphoma cells and indicated CR in only one case (14%) at 362 days, partial regression in five cases at 130-431 days (average 227 +/- 114 days), and no change in one case at 91 days after eradication.

CONCLUSIONS

: These results suggest that CR of low-grade MALT lymphoma can be predicted at 1 to 2 months after eradication therapy by checking histological changes of MALT lymphoma cells.

Pancreatic endocrine tumor with signet ring cell features: a case report with novel ultrastructural observations

The case of a malignant pancreatic endocrine neoplasm with an unusual signet ring cell appearance is reported. The tumor was resected from a 30-year-old man with a 4.0-cm tumor in the body of the pancreas diagnosed by computerized tomographic (CT) scan. The resected tumor had a unique morphology characterized by numerous mucin-negative, signet ring cells, which were argyrophilic and immunoreactive for cytokeratin (CAM 5.2), chromogranin, synaptophysin, neuron specific enolase, and gastrin. Dense-core neurosecretory-type granules and numerous cytoplasmic lamellar inclusions were identified by electron microscopy. These inclusion bodies consisted of multilayered concentric osmiophilic lamellae (myelin figures), which most likely represent an abnormal accumulation of degenerating organelles. Two years later, the patient developed an abdominal recurrence of the tumor, confirming its malignant behavior. This case expands the spectrum of pancreatic endocrine tumors to include an aggressive signet ring cell tumor with a novel ultrastructural basis.

Synchronous mucosa-associated lymphoid tissue lymphoma and adenocarcinoma of the stomach

The development of simultaneous primary gastric lymphoma and carcinoma is a rare event for which a possible etiopathogenetic role for Helicobacter pylori (HP) recently has been postulated. We report a series of eight such cases diagnosed from 1980 to 1995. In two cases, both tumors arose in a gastric stump, at 26 and 34 years, respectively, after gastric resection for a duodenal ulcer. Grossly, the lymphoma and carcinoma formed a single lesion in four cases (collision tumor); they were separated in the other four cases. Histologically, all the lymphomas fit into the category of B-cell mucosa-associated lymphoid tissue lymphoma; six of them were low-grade lymphomas and two were low-grade lymphomas with a high-grade component. The adenocarcinomas were intestinal-type in four cases, diffuse in three, and mixed in one. Regarding the depth of infiltration, four carcinomas were early gastric cancers and four were advanced. All the collision tumors contained an early gastric cancer. Our observations confirmed the association of HP with gastric lymphoma and carcinoma in 4 cases. Spiral bacteria with the features of Helicobacter heilmannii were found in one case. The occurrence of two different tumors in a gastric stump, which has not been reported previously, suggests that postgastrectomy gastritis might contribute to the development of both gastric lymphoma and carcinoma.