PMC5994652_01
PET-scan imaging. A, B PET-scan of July 2014 at time of diagnosis, showing hypermetabolic cervical, mediastinal and hilar lymphadenopathies (red arrows). There was no digestive localization. C, D PET-scan of October 2016, showing pulmonary FDG uptake compatible with lung infection. No suspect FDG uptake of lymphoma recurrence or digestive uptake was found
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Fig1
In July 2014, a 55-year-old Caucasian man with cervical and mediastinal polyadenopathies was diagnosed with a non-Hodgkin follicular lymphoma (WHO grade 2) in our institution (Fig. 1A, B). We noted only the appearance of lung lesions of infectious appearance without concomitant respiratory and infectious clinical symptoms (Fig. 1C, D).
Timeline of patient's care
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Fig2
Six monthly cycles were delivered, with good tolerance and complete metabolic response (PET-scan of October 2015), then followed by maintenance rituximab (375 mg/m2, 1 injection every 2 months) started in December 2015 and planned for 2 years (Fig. 2).  
Colonoscopy imaging. Colonoscopy of June 2016 showing sigmoiditis, with a 4-mm-depth rectal ulceration (black arrow) at 20 cm of the anal canal, compatible with ulcerative colitis
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Fig3
Colonoscopy showed sigmoiditis, with a 4-mm-depth rectal ulceration at 20 cm of the anal canal (Fig. 3), compatible with ulcerative colitis.
Pathological aspect of the rectal Kaposi's sarcoma. a Microscopic aspect of the biopsy of rectal ulceration: the rectal mucosa is infiltrated by an ill-defined cellular fasciculated to diffuse proliferation (HES x10). b Microscopic aspect showing spindle cells with little to moderate nuclear atypia surround vascular clefts. Few mitoses are noted. Lymphocytes and plasma cells are admixed (HES x40). c IHC with ERG antibody: the lining cells of vascular structures and spindle cells express the ERG endothelial marker (x20). d IHC with HHV8 antibody: see the nuclear positive immunostaining of spindle tumor cells (x40)
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Fig4
The diagnosis of rectal Kaposi's sarcoma was confirmed in October 2016: there was an ill-defined, fasciculated to diffuse proliferation of spindle cells with little to moderate nuclear atypia and few mitoses, outlining vascular slots; IHC showed positive staining of tumor cells for CD31 and ERG endothelial markers and for HHV8, and negative staining for CD117, DOG1, and STAT6 (Fig. 4).