Mantle cell lymphoma is an uncommon subtype of B-cell lymphoma, affecting more predominantly men. The most frequent presentation is the classic form, also called nodal. In this variant, lymphadenopathy is common, and splenomegaly may also occur. Peripheral blood involvement is often observed in this disease, presenting as small and medium-sized pleomorphic lymphoid cells with irregular nuclear contours. The absolute lymphocyte count may also be increased. However, presentation as a Sister Mary Joseph's nodule is quite uncommon in this lymphoma.

A 57-year-old man, previously hypertensive, reports swelling in the umbilical region, weight loss, fever and night sweats. He presented to an emergency department, where anemia was identified and a hypothesis of umbilical hernia was made. He reports that over the months, the condition progressed, with worsening of the umbilical nodular lesion, reaching 6.6 cm, with erythema and ulceration. In addition, he also refers a progressive increase in abdominal volume, due to the appearance of ascites and splenomegaly, as well as generalized lymph node enlargement. In this context, he was referred to our service for a hematology consultation. In the initial exams, a normocytic normochromic anemia (Hb 7.7 g/dL) was observed, as well as leukocytosis (12160 cells), at the expense of 56% of lymphocytes (in the automated counter). In the peripheral blood smear, pleomorphic lymphoid cells were identified. CT scans were performed, which showed bilateral pleural effusion; multiple abdominal and pelvic retroperitoneal lymph node enlargement, as well as mesenteric lymph node enlargement, in addition to homogeneous splenomegaly and moderate ascites. Signs of diffuse peritoneal thickening were also observed, notably in the lesser omentum. The PET Scan confirmed an increased uptake both in the mesentery and in the umbilical region.

Sister Mary Joseph's nodule occurs in several neoplasms that course with metastatic intra-abdominal disease. However, its occurrence as a signal from mantle cell lymphoma is quite rare, and this is the third description found after reviewing the literature. According to a series of cases with 68 patients, this finding occurs mainly with pancreatic (17.7%), gastric (17.7%), ovarian (16.2%), colonic (10.2%) and endometrial (8.8%). Hematological tumors account for only 7.4% of cases. Extranodal involvement by mantle cell lymphoma occurs mainly in the gastrointestinal tract, in up to about 15% of cases, with colonic involvement being the most prevalent, followed by gastric involvement. In endoscopic findings, the classic description is as lymphomatoid polyposis, although isolated polyps, masses and even intact mucosa with microscopic confirmation can also be found. About the prognostic impact of this finding, a retrospective analysis of 64 patients with gastrointestinal involvement in mantle cell lymphomas showed a statistical trend towards greater recurrence of the disease in this subgroup. Therefore, the predilection for gastrointestinal tract involvement by this subtype of NHL could explain the unusual clinical finding of this patient.

Sister Mary Joseph's nodule, although not a common topography, should be considered in the differential diagnosis and staging of mantle cell lymphomas.