EP814 - Isolated Gastrointestinal Kaposi Sarcoma

Purpose/Background: Kaposi Sarcoma (KS) is a rare neoplasm associated with HIV/AIDS and immunosuppressed populations caused by the Human Herpes Virus 8 (HHV8). KS is an angioproliferative tumor that classically presents with reddish-blue cutaneous lesions that easily bleed. Rarely, patients with KS can present without cutaneous lesions. Involvement of the GI tract occurs in about 40-50% of patients with cutaneous KS. However, isolated gastrointestinal manifestations without cutaneous lesions are exceedingly rare.

Methods/Interventions: We describe the case of a 56 year-old male with no past medical history but complex social history who presented with severe rectal pain. His initial complaint in December 2024 was a gluteal abscess. He was seen by a community colorectal surgeon and started on antibiotics, but re-presented with continued pain, incontinence, fevers, fatigue and night sweats. He received a colonoscopy which was reportedly normal and no biopsies were taken. He underwent an exam under anesthesia (EUA) in February 2025, where a perianal fistula was found and seton placed. The patient continued to have pain and drainage. An MRI from April 2025 showed a semicircular low rectal neoplasm with an adjacent ulcerated mass in the left mesorectum with possible involvement of the prostate, pelvic sidewall and sphincters with bilateral extrasphincteric fistulas. He underwent another EUA with seton placement. Given the unclear diagnosis with no significant findings on his colonoscopy and EUAs, he presented to our tertiary referral center.

Results/Outcomes: On presentation to our institution in June 2025, a CT showed a large cavity with markedly thick irregular walls in the left ischioanal space communicating with the anal canal -concerning for malignancy within perianal fistulae. The patient underwent a flexible sigmoidoscopy and EUA which showed congested and friable rectal mucosa without an intraluminal mass. He also underwent a diverting colostomy to alleviate his severe pain and pelvic sepsis. Biopsies were taken and resulted in KS. The patient was found to be HIV positive (viral load 177000, but CD4 486) and started on Highly Active Antiretroviral Therapy (HAART) with continued monitoring of his KS and plans for systemic therapy if he does not respond.

Conclusion/Discussion: This patient's presentation with recurrent perirectal abscesses and perianal fistulae in the absence of typical cutaneous KS lesions and with a normal CD4 count is a rare occurrence with very few described in literature. Patients may experience diarrhea, pain, weight loss, bleeding or be asymptomatic. Endoscopically, these lesions vary and have been described as red-nodular lesions, hemorrhagic patches, discrete papules, exophytic projections, and volcano-like lesions with central umbilication. Biopsies may not always reveal the diagnosis due to submucosal involvement. Early diagnosis and immediate control of HIV/AIDS with HAART is the mainstay of treatment. Systemic chemotherapy is an option for patients with visceral involvement or progressive disease.

Flexible sigmoidoscopy from June 2025
MRI from June 2025