Crohn's Disease Diagnosis Following Discovery of In Situ Follicular Lymphoma

Crohn's disease (CD) is an idiopathic inflammatory disease that can involve the entire gastrointestinal tract (though the small intestines are most commonly affected) in a transmural fashion. CD is recurrent and slowly progressive, and it can affect multiple regions of the intestines with normal regions in between. In situ follicular lymphomas (ISFL) are lymphomas exhibiting focal germinal centers, containing centrocytes staining strongly for bcl-2 protein in an otherwise normal lymph node. In this report, we discuss a unique occurrence of ISFL in a patient who was ultimately diagnosed with CD. This case is valuable to both the clinician and the academic as it augments the current fund of knowledge by proposing a possible relationship between these 2 conditions that has yet to be documented in the literature. Included is a discussion of the prevalence and pathophysiology of both ISFL and CD, a presentation of the current connections between the 2 conditions from the current body of literature, and a presentation of workup and outcome of this unique case.

Crohn's disease affects an estimated 6–7.1 persons per 100,000 and presents most commonly in patients between 15 and 30 years old.¹ While colonoscopy still offers the most definitive diagnostic method, other options such as capsule endoscopy and small bowel follow-through studies offer an indirect method for diagnosing CD in patients where disease is limited to the small bowel (and inaccessible via traditional colonoscopy). The most common symptoms are abdominal pain, diarrhea, and weight loss, though many other symptoms are observed. The 3 main classifications of CD are ileal, ileocolic, and colonic.

Although cases have been presented where CD mimicked lymphomatous colitis,² there have been no cases presented to date where an ISFL was found to cause the presenting symptoms in a patient ultimately diagnosed with CD. Thus, this case is an important contribution to the body of medical knowledge, as it indicates that a connection might exist between CD and ISFL, a notion that has yet to be entertained in the medical literature.

CASE REPORT

A 26-year-old man presented complaining of fluctuating abdominal pain of 3 months' duration. He was afebrile, and his abdomen was soft with mild periumbilical tenderness and moderate-to-severe, intermittent periumbilical pain described as “an intense cramping” sensation. There were no peritoneal signs, and the patient reported overall constipation with occasional diarrhea. A weight loss of 13.63 kg (30 pounds) over 4 months was noted, but this weight loss was intentional and accomplished via an adequate diet and exercise. Ultrasound of the abdomen showed no liver, gallbladder, splenic, and or cholecystic abnormalities. Proton pump inhibitors were prescribed while further workup was performed, but they failed to ameliorate symptoms. Subsequently, various anticholinergics and a selective serotonin reuptake inhibitor (sertraline) were attempted for suspected irritable bowel syndrome, none of which provided the patient relief.

Computed axial tomography (CT) of the abdomen revealed multiple prominent lymph nodes along the bowel mesentery, with the largest node measuring 2.7 × 1 cm (Figure 1). Shotty retroperitoneal lymph nodes were also observed on the CT. Upper endoscopy revealed only a sliding hiatal hernia, and biopsies taken of the small bowel were negative for celiac disease and active duodenitis, while gastric biopsies showed reactive gastritis with no evidence of Helicobacter pylori infection. Tissue transglutaminase antibody levels (IgA) were within normal limits. Cultures showed no evidence of campylobacter, Clostridium difficile toxin, salmonella, or shigella infection, and no ova or parasites were visible in stool samples. Colonoscopy showed no abnormalities from the anus to the terminal ileum. Mesenteric lymph node biopsy was obtained via fine-needle aspiration and nonspecific, focal noncaseating granulomatous reactions were observed. Since no definite neoplastic processes were seen, the main differential diagnosis centered on infectious vs noninfectious etiologies.

Figure 1.

Largest (2.7 × 1 cm) of multiple lymph nodes observed along the bowel mesentery via computed axial tomography of the abdomen.

Follow-up laparoscopic biopsy showed an enlarged lymph node with preserved architecture and widely patent sinuses with sinus histiocytosis. Numerous follicles were present that appeared reactive with a starry-sky pattern and intact mantle zones. Moderate numbers of small, noncaseating granulomas were present in all sections.

Histo-immunopathology

The histologic features were benign, and the presence of granulomas raised the possibility of an infectious process such as mycobacterial infection or an early stage of Whipple's disease. Periodic acid-Schiff (PAS) and acid-fast stains were negative for microorganisms. Immunostains showed a normal distribution of CD20+ B cells and CD3+ CD5 T cells. Plasma cells were numerous both within follicles and in the interfollicular region. Some follicles showed apparent light-chain restriction of either kappa or lambda type, but since follicles are normally of restrictive clonality, this feature was not worrisome.

What was most unusual was that scattered follicles on every block showed variable numbers of strongly staining bcl-2+ B cells, sometimes filling the entire follicle, and sometimes comprising only a proportion of the cells. Said cells did not appear to show any abnormal expression of bcl-6 or CD10, and the Ki-67 fraction was high in all the follicles. Stains for cytomegalovirus, CD15, and CD30 were noncontributory. Review of hematoxylin and eosin stains to correlate the morphology of the bcl-2+ follicles was difficult due to the small size of most of the follicles and difficulty in finding the same follicle on 2 different sections. The follicles did not appear very monomorphous, despite somewhat thick histologic sections (with some artifact), making the interpretation difficult.

Finally, capsule endoscopy showed diffuse mucosal abnormalities (especially in the jejunum and proximal ileum) with apthous ulcers and skip lesions compatible with Crohn's disease (Figure 2). Treatment with oral mesalamine (5-ASA) apparently decreased inflammation in the bowel, leading to significant relief of the patient's symptoms. Treatment with oral steroids (eg prednisone), monoclonal antibody against TNFα (eg infliximab), and immunosuppressants (eg azathioprine) was not pursued in light of a complete reduction of the patients symptoms on oral mesalamine alone.

Figure 2.

Apthous ulcers (circled) were present during capsule colonoscopy.

DISCUSSION

Although cases have been presented that report a connection between lymphomatous conditions and Crohn's disease, there have been no cases presented to date where an in situ follicular lymphoma (ISFL) was found in conjunction with CD. Papers reporting the connection between lymphomatous conditions and CD are present in the literature including a case of vulvar Hodgkin lymphoma,³ vulvar squamous cell carcinoma,⁴ primary Hodgkin disease of the terminal ileum (with concurrent Epstein-Barr infection),⁵ primary gastrointestinal lymphoma of the ileum,⁶ and extraintestinal Hodgkin's disease.⁷ Additionally, a case has been reported where CD mimicked lymphomatous colitis.² What is still not described in the literature, however, is a report and discussion of a potential pathophysiologic connection between CD and ISFL, as presented herein.

Crohn's Disease

Crohn's disease is the namesake of American gastroenterologist Burrill Bernard Crohn, who, in 1932 with 2 colleagues, discovered a series of patients with inflammation of the terminal ileum (the most common portion of the gastrointestinal tract affected by the illness).⁸ While the etiology of CD is unknown, several have postulated the origin as infectious (Mycobacterium avium),⁹ while others claim such theories of “molecular mimicry” (between mycobacterial stress protein antigens and their human homologs leading to autoimmune disease) are unsubstantiated.¹⁰ Most believe that CD results from a combination of microbiotic, intestinal epithelial, and mucosal immune response/dysfunction.¹¹

Despite its unknown etiology, it is agreed that CD begins with crypt inflammation and abscesses that give way to tiny focal aphthoid ulcers. The mucosal lesions often develop into longitudinal and transverse ulcers with intervening mucosal edema. As the inflammation spreads in a transmural fashion, lymphedema and thickening of the bowel wall and mesentery are likely to occur causing enlarged mesenteric lymph nodes. As discussed later in this manuscript, we offer that the mesenteric lymphadenopathy observed in this case may be the result of CD and not the result of neoplastic processes.

Clinical presentations of CD vary more than those of ulcerative colitis due to the unpredictability of the extent of disease and transmural involvement. Common signs and symptoms include fatigue, abdominal pain, weight loss, prolonged diarrhea, and fever, with or without gross bleeding. It should be noted, however, that as many as 10% of patients diagnosed with CD do not have diarrhea.

Although CD presents in many different forms and to varying degrees, the course typically consists of intermittent exacerbations of symptoms followed by periods of remission. According to one study,¹² a severe course can be predicted when the patient is less than 40 years of age, has perianal disease, and initially requires corticosteroids. Additionally, 10%–20% of patients enjoy a prolonged period of remission after their initial presentation.¹³ The American College of Gastroenterology¹⁴ recently stated that “patients who have active disease within the past year have a 70% chance of remaining active in the forthcoming year and a 50% chance of being in remission within the ensuing 3 years” and that “fewer than 5% [of patients with CD] will have a continuous course of active disease.” Various studies attempting to determine whether the overall life expectancy of patients with CD is decreased have produced incongruent results suggesting that CD may have little if any effect on overall life expectancy.

The current treatment suggestions for CD vary depending on the severity of the disease. For mild, ileocolic disease, remission is generally induced with corticosteroids (eg prednisone), enteral nutrition, mesalamine, and/or antibiotics (though antibiotics have only been proven to offer relief in cases of perianal fistulas). After remission is achieved, maintenance therapy is commenced (usually aminosalicylates alone and/or a thiopurine [6-mercaptopurine or azathioprine]). If the patient's disease flares and/or moderate to severe CD is present, corticosteroids may be used with or without thiopurine (to reduce the potential for patients to become refractory to or dependent on steroids). If patients are intolerant to the above regimen, infliximab, methotrexate, or occasionally surgical resection of a discrete diseased segment of the bowel may be suitable options.¹⁵

In Situ Follicular Lymphoma

In situ follicular lymphoma is a fairly recent classification of lymphoma in which a translocation between chromosomes 14 and 18 is seen. These t(14;18)-positive cells expressing bcl-2 are observed in histologically abnormal follicles found in lymph-node biopsy specimens of patients without frank follicular lymphoma (FL). The condition describes the presence of focal germinal centers containing centrocytes staining strongly for bcl-2 protein in an otherwise normal lymph node.¹⁶ This strong staining for bcl-2 is of unclear significance, as there is no apparent direct correlation between the developments of FL from ISFL.¹⁷ Moreover, making the distinction between overt follicular lymphoma and ISFL is at this stage difficult to impossible, given the current knowledge of ISFL.¹⁸

The etiology has been proposed to be due to the development of a clonogenic cell containing t(14;18) arising at the pre–B-cell stage (ie within the bone marrow) as an error of D-J or V-DJ joining. This B cell with a t(14;18) translocation enters the circulation and homes to a lymph node, eventually seeding a lymphoid follicle. Adding to this etiologic theory, other observers have postulated that clonal expansion may then occur following antigenic stimulation, and assuming a “second hit” fails to occur, the patient will not develop frank follicular lymphoma despite the presence of cells with the t(14;18) transformation.¹⁹ In other words, this phenomenon may represent follicular involvement of B cell clones that have bcl-2 rearrangement (which may, incidentally, be found in the peripheral blood and tissues of the majority of healthy individuals in the population). Upon entering reactive follicles, these cells may expand; however, they do not appear to contain the genetic abnormalities necessary for frank lymphoma development.¹¹

In the single extensive study of ISFL to date,¹⁷ most cases were discovered incidentally (as in this patient). The majority of patients in said study did not develop evidence of overt follicular lymphoma, though some were found to have either a history of follicular lymphoma or overt follicular lymphoma in other nodes simultaneously. Due to a lack of thorough, extended follow-up of patients presenting with ISFL, the optimal management for the condition has yet to be identified.

In patients where ISFL is observed, frank FL can develop within a few years, in more than a decade, or may never occur. This variance suggests that ISFL may represent a preneoplastic stage in its pathogenesis toward FL. Though the epidemiology of ISFL has yet to be studied, the incidence of overt FL approximates 1 case per 24,000 persons per year in the United States. It should be noted, however, that normal B cells with t(14;18) rarely undergo transmutation into FL (as t(14;18) can be found in more than 50% of healthy persons).^17,19

Immunostaining

Immunostains are the current standard for evaluating and diagnosing lymphomas. In this case, the patient exhibited a normal distribution of CD20+ B cells. CD20 is a nonglycosylated phosphoprotein expressed on the surface of B cells in all but pro-B and plasma cells. Its presence would suggest conditions such as B-cell lymphomas, hairy cell leukemia, and B-cell chronic lymphocytic leukemia.²⁰ The patient's level of CD3+CD5+ T cells was also found to have a nonpathologic distribution. CD3 acts with the ζ-chain and T cell receptor to generate an activation signal in T lymphocytes, while CD5 serves to alleviate activating signals from the B cell receptor, limiting B-1 cell activation to signals from significant stimuli (ie not signaled by normal tissue proteins). An abnormal distribution of CD3+CD5+ T cells would have suggested conditions such as mantle cell lymphoma or small lymphocytic lymphoma.

In this case, the presence of bcl-2+B cells varied between filling the entire follicle and comprising only a proportion of the cells, an anomalous finding. In follicular lymphomas, a t(14;18) (chromosomal translocation between chromosomes 14 and 18) occurs, positioning the bcl-2 gene next to the immunoglobulin heavy chain locus. The result of this fusion is a deregulation of transcription of bcl-2, leading to elevated expression.²¹ Such a translocation decreases the propensity of these cells for undergoing apoptosis and can lead to unrestrained cell propogation.

No abnormal expression of bcl-6 was found in this case. Bcl-6 is a sequence-specific repressor of transcription and has been demonstrated to adapt the transcription of STAT-dependent interleukin 4 responses of B cells. It has been found to be mutated and translocated [t(3;Var)(q27;Var)] in diffuse large B cell lymphoma and has been speculated to have a role in its pathogenesis.²²

The expression of CD10 in this patient was found to be within normal limits, suggesting that a diagnosis of diffuse large B-cell lymphoma (DLBCL) was unlikely. Although the prognostic value and relevance of CD10 in de novo DLBCL is largely unknown, one study found that CD10 expression may be of prognostic importance in adults with de novo DLBCL. The study retrospectively examined a small group (19 men and 9 women) of patients with DLBCL. Of the 28 cases examined, 11 patients were CD10+, and 17 were CD10-, with no significant differences between the CD10+ and CD10- groups with respect to age, sex, stage, extranodal involvement, or serum lactate dehydrogenase levels at diagnosis. When follow-up data were analyzed it was determined that the CD10+ group exhibited a shorter overall survival than the CD10- group (8 vs 30 months). Ultimately it was determined that despite similarities in the clinical findings at the time of diagnosis between patients with CD10+ and CD10- DLBCL, CD10 expression itself appears to be associated with an overall shortened survival rate.²³

In this case, the Ki-67 fraction was found to be high in all the follicles biopsied. The Ki-67 protein (also known as MKI67) is a cellular marker for proliferation and appears to be strictly associated with cell proliferation.²⁴ During interphase, the Ki-67 antigen is detectable within the nucleus, while most of the protein relocates to the chromosomal surface in mitosis. While Ki-67 protein is not detectable in resting cells (G0), it can be isolated during all active phases of the cell cycle (G1, S, G2, and mitosis).²⁵ As such, the fraction of Ki-67-positive cells (also known as the Ki-67 labeling index) can be correlated with the clinical course of lymphomas and cancers (especially carcinomas of the prostate and the breast).

CONCLUSION

We propose that the ISFL diagnosed via mesenteric lymph-node biopsy in this patient may be related to the presence of an early onset of Crohn's disease, verified via capsule endoscopy. As stated previously, the mesenteric lymphadenopathy observed in this patient was possibly due to lymphedema and thickening of the bowel wall and mesentery secondary to Crohn's disease. Additionally, it is possible that the increased Ki-67 fraction was elevated due to cellular proliferation caused by CD and that the patient in this case is part of the 50% of the population of healthy persons who exhibit B cells with a t(14;18) transformation.

We present this case and hypothesis with the hope that a dialogue will begin between clinicians and researchers regarding the possible connection(s) between CD and ISFL. In so doing, a better understanding of each disease process may be achieved as the principles of this case are used in conjunction with the workup and treatment of other patients.