Rectal mantle cell lymphoma endoscopically mimicking ulcerative proctitis: A case report

Abstract

BACKGROUND

Mantle cell lymphoma (MCL) is a mature B-cell non-Hodgkin lymphoma characterized by a chromosomal translocation between chromosomes 11 and 14, resulting in cyclin D1 overexpression. MCL frequently involves extranodal sites, including the bone marrow, spleen, liver, and gastrointestinal tract. However, rectal involvement is exceedingly rare and sparsely reported in the medical literature.

CASE SUMMARY

We report a case of rectal MCL initially misdiagnosed as ulcerative proctitis based on endoscopic findings, highlighting the importance of histopathological evaluation in atypical presentations of proctitis.

CONCLUSION

This case highlights an important clinical message: MCL should be included in the differential diagnosis of rectal bleeding when endoscopic findings resemble ulcerative colitis or proctitis. Awareness of this rare presentation may facilitate earlier diagnosis and appropriate oncologic management.

Key Words: Mantle cell lymphoma; Ulcerative proctitis; Endoscopic mimicry; Rectum; Rectal bleeding; Case report

Core Tip: This case highlights an important clinical message: Mantle cell lymphoma should be included in the differential diagnosis of rectal bleeding when endoscopic findings resemble ulcerative colitis or proctitis. Awareness of this rare presentation may facilitate earlier diagnosis and appropriate oncologic management. Given the rarity of gastrointestinal involvement, particularly at the rectal level, prospective studies are needed to better define optimal therapeutic strategies and improve clinical outcomes in this subset of patients.

INTRODUCTION

Mantle cell lymphoma (MCL) is a mature B-cell non-Hodgkin lymphoma that accounts for approximately 3%-6% of all lymphomas[1]. It is characterized by the chromosomal translocation t(11;14)(q13;q32), leading to overexpression of cyclin D1 and dysregulated cell cycle progression[2]. MCL predominantly affects older adults, with a male predominance and a median age at diagnosis in the sixth decade of life[3]. Extranodal involvement is common in MCL, particularly affecting the bone marrow, spleen, liver, and gastrointestinal tract[4]. Gastrointestinal involvement often presents as multiple lymphomatous polyposis; however, primary rectal involvement is extremely rare[3,4]. We present a case of rectal MCL in a 79-year-old female who presented with rectorrhagia and whose initial endoscopic appearance was suggestive of ulcerative proctitis, underscoring the diagnostic challenge posed by this uncommon presentation.

CASE PRESENTATION

Chief complaints

A 79-year-old female presented to the gastroenterology department with rectorrhagia.

History of present illness

She denied abdominal pain, weight loss, vomiting, altered bowel habits or fever.

History of past illness

There was no personal or family history of gastrointestinal malignancy.

Personal and family history

Patient denies any personal or family history.

Physical examination

Physical examination was unremarkable.

Laboratory examinations

Laboratory investigations, including lactate dehydrogenase and beta-2 microglobulin, were within normal limits. The patient has an Eastern Cooperative Oncology Group performance status of zero.

Imaging examinations

Colonoscopy revealed erythematous rectal mucosa with non-specific superficial erosions and loss of the normal vascular pattern (Figure 1). The Ulcerative Colitis Endoscopic Index of Severity (UCEIS) score was 5 out of 8, favoring a diagnosis of ulcerative proctitis. Multiple rectal biopsies were obtained for histopathological evaluation.

Figure 1 Colonoscopic images at the level of the rectum. The figure revealing marked erythematous mucosa and moderate friability (black arrows) with visible erosions (blue arrow) and partial loss of vascular pattern with an Ulcerative Colitis Endoscopic Index of Severity score 5/8.

A scanner thoraco-abdomen-pelvis was done which revealed hepatosplenomegaly along with celiac, mesenteric and left external iliac lymphadenopathy. No mass was seen at the level of the rectum (Figure 2A and B). A positron emission tomography (PET) scan was performed for staging and revealed hypermetabolic activity in both supra- and subdiaphragmatic lymph nodes, with a maximum standardized uptake value of 4.3 in the left external iliac lymph nodes, as well as splenic involvement. No abnormal metabolic activity was detected at the rectal level (Figure 3A and B).

Figure 2 Scanner thoraco-abdomen-pelvis findings. A: Scan thoraco-abdomen-pelvis revealing hepatosplenomegaly (blue arrows). Celiac, mesenteric lymphadenopathy (orange arrow); B: Left external iliac lymphadenopathy (orange arrow). No mass was seen at the level of the rectum (yellow arrow).

Figure 3 Positron emission tomography findings. A: Positron emission tomography revealing hypermetabolism at the level of the spleen with splenomegaly; B: Positron emission tomography revealing a hypermetabolic activity with a maximum standardized uptake value of 4.3 in the left external iliac lymph nodes. No abnormal metabolic activity was detected at the rectal level (white arrow).

FINAL DIAGNOSIS

Hematoxylin and eosin staining, along with immunohistochemical analysis, confirmed the diagnosis of MCL, classic type (Figure 4). Immunohistochemistry demonstrated a B-cell population positive for CD20 and CD5, and negative for CD3. Tumor cells showed positivity for cyclin D1 and BCL2, and were negative for CD10, BCL6, and CD23 (Figure 5). The Ki-67 proliferation index was approximately 15%. The patient’s MCL is classified as Ann Arbor stage IV.

Figure 4 Histopathology showing diffuse proliferation of small lymphoid cells involving the lamina propria and submucosa, hematoxylin-eosin staining. A: 2 × magnification; B: 5 × magnification; C: 10 × magnification.

Figure 5 Immunohistochemistry staining of rectal mantle cell lymphoma. A: CD79a positive; B: CD5 positive; C: CD3; D: B-cell lymphoma-2 positive; E: Cyclin D1 positive; F: CD23 negative; G: CD10 negative; H: B-cell lymphoma-6 negative.

TREATMENT

The patient was referred to hematology and initiated on combination therapy with rituximab and bendamustine in the setting of a Mantle Cell International Prognostic score of two.

OUTCOME AND FOLLOW-UP

She remains under regular follow-up.

DISCUSSION

MCL is an uncommon B-cell non-Hodgkin lymphoma characterized by a heterogeneous and often aggressive clinical course[1,3]. It is frequently diagnosed at an advanced stage due to its nonspecific clinical manifestations and its propensity for extranodal involvement. Gastrointestinal tract involvement by MCL is relatively rare, occurring in approximately 4%-9% of cases, with the terminal ileum being the most frequently affected site, reported in 35%-48% of patients. Rectal involvement is particularly uncommon, accounting for approximately 6% of gastrointestinal cases[5].

Within the gastrointestinal tract, MCL typically infiltrates the submucosal layer, which may limit the sensitivity of superficial mucosal biopsies and contribute to diagnostic challenges[6]. Endoscopic manifestations are variable and may include multiple lymphomatous polyposis, erosions, erythema, or ulcerations, occasionally mimicking inflammatory bowel disease. As demonstrated in the present case, rectal MCL may closely resemble ulcerative proctitis on endoscopic examination, underscoring the critical role of histopathological and immunohistochemical analysis for definitive diagnosis.

Endoscopic resection is often not feasible in MCL, particularly in cases with deep submucosal invasion or when endoscopic findings are nonspecific, including unclear vascular or pit patterns on chromoendoscopy and magnifying endoscopy. Therefore, targeted biopsies remain essential for diagnostic confirmation, even in the absence of classic endoscopic features of lymphoma[7].

Compared with other indolent small B-cell lymphomas, MCL generally exhibits a more aggressive behavior, with a historically reported median overall survival of approximately 3-5 years[6,7]. Given the rarity of gastrointestinal involvement, particularly at the rectal level, prospective studies are needed to better define optimal therapeutic strategies and improve clinical outcomes in this subset of patients.

Owing to its endoscopic resemblance to ulcerative procititis, the rectal lesion was initially given an UCEIS score of an 5/8 characterized by the presence of bleeding (+1), ulcers, erosions (+2) and loss of the vascular pattern (+2). Therefore, this is how UCEIS contributed to the initial diagnostic impression.

An extensive lymphomatous infiltration may produce mucosal erythema, vascular loss, and friability and effacement of mucosal folds mimicking inflammatory bowel disease further posing a diagnostic challenge.

The absence of abnormal metabolic activity at the rectal level on PET imaging, despite histopathological confirmation of lymphoma, is an important observation that makes our case report unusual. Submucosal infiltration, low tumor burden, or a relatively low Ki-67 proliferation index (15%) are potential explanations that address the radiological-pathological discordance in this case report. MCL frequently involves the submucosa, which may limit detection on superficial biopsies and reduce sensitivity on PET imaging in low-proliferative disease.

A rituximab-bendamustine (BR) therapy was selected over alternative regimens such as rituximab, cyclophosphamide, hydroxydaunomycin, oncovin, prednisone, particularly in the context of patient age, performance status, and Mantle Cell International Prognostic score. In fact, Kotchetkov et al[8] conducted a single center observational study regarding BR tolerability and efficacy in the treatment of indolent non-Hodgkin's lymphoma and MCL in elderly. The study has concluded that BR is well-tolerated and elderly patients had lower incidence of febrile neutropenia. Dose reduction and treatment delays are common, but BR efficacy was not affected even in very old patients (≥ 80 years)[8].

CONCLUSION

This case highlights an important clinical message: MCL should be included in the differential diagnosis of rectal bleeding when endoscopic findings resemble ulcerative colitis or proctitis. Awareness of this rare presentation may facilitate earlier diagnosis and appropriate oncologic management.