Mantle cell lymphoma is an aggressive low-grade B cell non-Hodgkin's lymphoma with a prevalence of approximately 6% of all NHL [1]. The incidence rate of MCL is 0.8 per 100,000 people, according to the SEER database (Surveillance, Epidemiology, and End Results Program) [2]. According to a previous retrospective study, the prevalence is 5.6% in the Indian population [3]. The median age at presentation is between 60 and 65 years, and it is more prevalent in men. Having a pathognomonic chromosomal translocation (11;14) and overexpression of cyclin D1 are hallmarks of the uncommon and aggressive B-cell non-Hodgkin's lymphoma known as mantle cell lymphoma [4]. Prior to the introduction of rituximab antibody treatment and autologous stem cell transplantation (SCT), the prognosis for MCL was generally poor; now, results have considerably improved with long-term disease-free survival [4-6]. Histomorphology, immunohistochemistry, and evidence of overexpression of the cyclin-D1 MCL protein by immunophenotyping and/or fluorescence in-situ hybridization (FISH) are used to make the diagnosis of MCL [7]. In this rare case report, our primary aim was to describe the rare presentation of MCL patients as rectal nodules and to discuss the histomorphology, immunophenotyping, and options for treatment for such patients.

We report a 59-year-old man who presented to the gastroenterology unit with chief complaints of rectal bleeding, constipation, and abdominal pain over the previous four months. There were no B symptoms. Hemogram, albumin, lactate dehydrogenase, urea, creatinine, electrolyte levels, and coagulation profile were all in the normal range. A colonoscopy revealed erythema, edema, loss of vascularity and nodularity with central ulceration present circumferentially involving the rectum [Fig.1a,b]. A contrast-enhanced computed tomography (CECT) of the thorax and abdomen was ordered, which showed no organomegaly and lymphadenopathy. On the basis of clinical presentation and colonoscopy findings, differential diagnoses of rectal carcinoma and lymphoma were kept in mind. A colonoscopy-guided punch biopsy of the rectal lesion was ordered based on the clinical manifestation and endoscopic findings. Histopathological analysis of the hematoxylin-eosin (H-E) stained sections from colonoscopy guided punch biopsy revealed diffuse infiltration of the lamina propria, and muscularis mucosae by atypical small-sized lymphoid cells disposed in nests and sheets displaying irregular nuclei, coarse chromatin, and a scant amount of cytoplasm [Fig.1c,d]. Based on the above histomorphology, we made the differential diagnosis of poorly differentiated carcinoma, small cell lymphoma, marginal zone lymphoma, and mantle cell lymphoma. An immunohistochemistry panel was applied which showed positive expression of leucocyte common antigen (LCA/CD45), CD20, CD5, and cyclin D1 in atypical lymphoid cells. Ki67 proliferation was 35-40%. CD3, CD10, and cytokeratin (CK) were negative in atypical lymphoid cells [Fig.2]. Based on the above histomorphology and immunohistochemistry, a diagnosis of mantle cell lymphoma was rendered. A bone marrow examination was also performed to stage the disease, which revealed normal haemopoiesis and was negative for lymphomatous infiltration. 18-fluorodeoxyglucose did not show uptake in any organ of body on PET scan. He was referred to the Clinical Hematology department for chemotherapy. The patient had received two cycles of rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) therapy and currently doing well.

The mantle cell type of the neoplastic lymphoid neoplasm was identified in 1984 [8,9]. In the Romaguera et al. study, it was noted that 88% of MCL patients had lower gastrointestinal system (GIS) involvement, compared to 43% of MCL patients who had upper GIS involvement [9]. The colon and rectum (57.1% and 47.6%, respectively) for the lower GIS and the stomach mucosa (74%) for the upper GIS are the most frequently affected sites. According to the endoscopic examination of the lesions within the GIS, the multiple lymphomatous polyposis (MLP) type is the most prevalent type (80%), whereas protruding nodular lesions are less common (18%). [10,11]. The endoscopic appearance of lesions is very variable and the clinical signs are non-specific; polyps, rectal ulcers, a solitary mass, or widespread mucosal thickening may all be present in addition to normal mucosa. Morbidity and death are prevalently high among cases of MCL associated with the gastrointestinal system [12]. Men are more likely to be affected, and symptoms often appear in their fifth or sixth decade of life [13]. Abdominal discomfort, diarrhoea, or haematochezia symptoms are frequently present. The majority of patients have extra-intestinal involvement and are present at an advanced stage. The bone marrow, peripheral lymph nodes, liver, and Waldeyer's ring, are the primary extra-gastrointestinal sites affected [14,15]. The atypical lymphoid cells in MCL are small to medium-sized and display uneven nuclear outlines, coarse chromatin, inconspicuous nucleoli, and a scant cytoplasm [14]. Mantle cell lymphoma express CD5 and pan B-cell antigens (CD19, CD20, and CD22) on immunohistochemistry but are negative for CD10 or CD23 expression. Despite the fact that 84% of mantle cell lymphoma patients, regardless of the existence of gastrointestinal symptoms, have some degree of microscopic gastrointestinal involvement [9], only 4 to 9% of all primary gastrointestinal B cell lymphomas are primary MCL [15]. Gastrointestinal mantle cell lymphoma is the most common cause of multiple lymphomatous polyposis (MLP). Even with the best treatment, multiple lymphomatous polyposis has a mean survival rate of about three years [16]. 

Lymphoproliferative  neoplasm should be considered in the differential diagnosis if patients present with rectal bleeding with rectal nodularity, especially at an advanced age. Immunohistochemistry is a great way to make definitive diagnosis, because symptoms and results of a colonoscopy and histomorphology findings may mimic with rectal carcinoma.

Contributors: AnS did study designing, data acquisition, manuscript writing and literature search. SM did a literature search and proof correction. NS did conceptual analysis and designing. AkS did proof reading. TT contributed to literature searches. SM will act as a study guarantor. All authors approved the final version of this manuscript and are responsible for all aspects of this case study.

Funding: None; Competing interests: None stated.