Clinical History
A 40-year-old woman came to our attention with rectal bleeding, no chronic inflammatory or autoimmune disorder and laboratory findings in range. Rectal digital examination detected a solid lesion in the left side of the rectal wall.
Imaging Findings
The colonoscopy identified a polypoid lesion, located up to 4 cm from pectinea line, 3.5 cm in size, solid and easily bleeding. The biopsy was positive for extranodal marginal zone b-cell lymphoma of MALT type (CD20+, CD79a+, CD10+, CD5-). MRI showed a lesion 4 x 2.5 cm in size, located in the left side of the rectal wall, with regular margins, minimum infiltration of the mesorectum and homogeneous signal intensity: isointense on T1W, slightly hyperintense on T2W compared with adjacent muscle (Fig. 1). It showed contrast enhancement on post-contrast T1W (Fig. 2). On DWI (b value 800) it was hyperintense and hypointense on ADC Map (Fig. 3). One oval mesorectal lymph nodes, 10x6 mm in size, was identified. Total body CT examination did not show other sites of pathology. The bone-marrow biopsy was negative for malignancy. Tumour stage, according to Ann Arbor system modified by Musshoff: I
Discussion
Primary rectal lymphoma is a rare disorder: 0.1-1% of all primary rectal tumours [1]. It is prevalent in male patients between the ages of 50 and 70 years. Possible risk factors include inflammatory bowel disease, immune-suppression and pelvic irradiation. Clinical presentation in the majority of cases is nonspecific and it can be comparable with rectal carcinoma, including; anorexia, weight loss, rectal bleeding, tenesmus and palpable mass [2].
Rectal lymphomas are predominantly of the non-Hodgkin type that are classified by WHO into some different subtypes: diffuse large b-cell (60%), extra-nodal marginal zone lymphoma (mucosa-associated lymphoid tissue [MALT]) (15%), Burkitt (15%), peripheral T cell, mantle cell and follicular cell. There are two types of MALT-lymphoma: the first one is chronic inflammatory or autoimmune disorder related, the second type originates from lymph nodal tissue such as Peyer patches like the case we report. Hodgkin disease is less than 5% of cases. The Ann Arbor system modified by Musshoff is the most common modality for staging gastrointestinal non Hodgkin lymphoma: stage I (single lymphatic organ involved), stage II (two or more lymphatic region on the same site of the diaphragm), stage III (both sides of diaphragm), stage IV (Disseminated disease) [3].
The biopsy of the lesion is essential for the diagnosis [4].
Imaging and endoscopy aspects of a rectal lymphoma can be really various and sometimes it is indistinguishable from adenocarcinoma. However, a lesion that is homogeneous, fairly well demarcated, without invasion of the adjacent structure, that shows a growing pattern prevalently longitudinal and circumferential, without desmoplastic reaction and that is rarely a cause of obstruction, is suggestive of lymphoma [5, 6].
MRI is fundamental for local staging while total body CT or PET/CT are essential for systemic staging; the bone-marrow biopsy is necessary to exclude a secondary lymphoma.
Actually there is no consensus about the treatment of choice and the follow-up of a rectal lymphoma [7]. The case we report presented a complete response at radiation therapy documented by PET/CT performed 6 months after the end of therapy. The patient was disease-free at 2 years follow-up.
Differential Diagnosis List
MALT lymphoma of the rectum
Rectal adenocarcinoma
Secondary lymphoma
Rectal gastrointestinal stromal tumour
Rectal haemangioma
Rectal carcinoid
Final Diagnosis
MALT lymphoma of the rectum
