Rare Case of Mantle Cell Lymphoma With Multiple Rectal Lesions

A 67-year-old man was referred for colonoscopy following a positive fecal occult blood test and the detection of thrombocytopenia. Clinically, the patient was asymptomatic. He was under oncological follow-up after previous surgical treatment for testicular cancer. During the colonoscopy, a laterally spreading tumor (LST) non-granular lesion measuring 25 × 20 mm was found in the upper rectum, classified as Paris IIa + IIc (Figure 1). The lesion was carefully evaluated using narrow band imaging (NBI) (Figure 2a) and magnifying endoscopy (Figure 2b). However, due to the unclear polyp surface and signs of pseudo-depression, biopsies were taken from the lesion. An additional five smaller lesions, each measuring 4–5 mm (Is), were found in the mid-rectum (Figure 3). All small polyps in the mid-rectum were resected using cold snare polypectomy. Histopathological examination (Figure 4a,b: HE staining, Figure 5a–d: Immunohistochemistry staining) confirmed the diagnosis of Mantle Cell Lymphoma (MCL) from both the main lesion and the smaller ones. Subsequently, the patient was referred to the Department of Hematology and Oncology, where standard staging procedures were completed. The disease was classified as stage IV A according to the Ann Arbor classification, with generalized lymphadenopathy identified on staging PET/CT imaging. Histological and flow cytometric analysis confirmed minor bone marrow infiltration. After six cycles of rituximab-based chemoimmunotherapy, the patient achieved complete remission of the lymphoma. High-definition white-light endoscopy (HD-WLE) image of an LST non-granular lesion in the upper rectum, classified as Paris IIa + IIc, measuring 25 × 20 mm. Endoscopic images—(a) LST non-granular lesion, classified as Paris IIa + IIc in NBI; (b) the same lesion viewed with NBI and magnifying endoscopy. Endoscopic image of diminutive non-pedunculated lesion in the mid-rectum, measuring 4–5 mm (Is), in HD-WLE. (a) Histopathology showing diffuse proliferation of small lymphoid cells involving the lamina propria and submucosa (red arrows), green arrow pointing normal colonic mucosa, Hematoxylin-Eosin (HE) staining, 40x magnification. (b) Histopathology of rectal mantle cell lymphoma showing a monomorphic population of small lymphoid cells with scant cytoplasm and irregular nuclei, HE staining, 200x magnification. (a) Immunohistochemistry (IHC) staining of rectal mantle cell lymphoma, CD3 negative, 200x magnification; only a few non-neoplastic T lymphocytes are positive (green arrows). (b) IHC staining of rectal mantle cell lymphoma, CD20 positive, 100x magnification; consistent with a B-cell phenotype. (c) IHC staining of rectal mantle cell lymphoma, CD5 positive, 100x magnification; showing aberrant co-expression. (d) IHC staining of rectal mantle cell lymphoma, Cyclin-D1 positive, 200x magnification, characteristic nuclear expression of MCL. MCL is a relatively rare B-cell lymphoma with a variable clinical course, typically diagnosed in an advanced stage of the disease, often with extranodal involvement [1]. The gastrointestinal tract is involved in about 4%–9% of all gastrointestinal B-cell non-Hodgkin lymphomas [2, 3]. The most common site of involvement is the terminal ileum in 35%–48% of cases, while rectal involvement is described in approximately 6% of cases [2, 3]. MCL originating usually from the submucous layer [4]. Endoscopically, MCL often presents as multiple lymphomatous polyposis (MLP) [2, 3], as observed in 43% of lymphomas according to a recent Japanese study [5]. Rectal neuroendocrine tumors should be considered in differential diagnoses, as they are typically small (commonly <10 mm), solitary, smooth, sessile yellowish subepithelial lesions with intact overlying mucosa, often located in the midrectum [6]. When evaluating rectal masses, even those presenting as solitary lesions that resemble adenocarcinoma, MCL should also be considered in the differential diagnosis [7]. Biopsies from the lesion are essential for establishing the correct diagnosis, especially when endoscopic resection (ER) is not feasible or when doubts about ER arise, such as in cases of deep invasion or unclear findings on chromoendoscopy and magnifying endoscopy (in terms of vascular and pit patterns, etc.). The authors have nothing to report. Consent has been received. The authors declare no conflicts of interest. The authors have nothing to report.