EXTRAMEDULLARY PLASMA CELL MYELOMA IN THE RECTUM: A DIAGNOSTIC CHALLENGE. CASE REPORT

Case Presentation CALS, 40 years old, male, was admitted to the emergency department presenting with anorectal bleeding, altered bowel habits, and a 15 kg weight loss over the past year, associated with asthenia, left hemiparesis, and dysarthria. He denies comorbidities. Admission exams revealed a history of ischemic stroke, as well as concentric thickening and stenosis in the distal rectum and anal canal, with lymph node involvement, suggesting neoplasia. During the pandemic, the patient lost follow-up with the Coloproctology team. Several endoscopic exams with biopsies were performed, all negative for neoplasia. A transanal biopsy was performed, along with immunohistochemistry, which revealed rectitis and chronic inflammatory processes. The patient continued to experience worsening symptoms and general health, including weight loss, diarrhea, intense proctalgia, and anorectal bleeding, requiring blood transfusions. Abdominoperineal amputation was recommended for diagnosis and treatment guidance, as complementary exams suggested neoplastic involvement. Despite initial reluctance, due to the persistent clinical condition, the patient agreed to undergo the procedure after 6 months. In 2024, he underwent abdominoperineal amputation (APA). The pathology report showed extramedullary plasmacytoma (EMP) in the rectum, with clear margins and three affected pelvic lymph nodes.

Discussion Plasmacytoma is a rare disease, affecting the upper aerodigestive tract in 80% of cases, and gastrointestinal involvement is rare. It is more common in males, with incidence increasing with age, typically around 60 years old. It is histopathologically confirmed by the presence of monoclonal plasma cell infiltration outside the bone marrow. The diagnosis is based on finding a monoclonal tumor in an extramedullary site, excluding multiple myeloma (MM). As with diagnosis, treatment is a challenge. Due to the tumor's radiosensitivity, radiation therapy (RT) is central to treatment. Surgery may be considered as a first-line treatment to avoid the long-term impact of RT, although it is frequently performed for recurrent tumors. Adjuvant chemotherapy remains controversial.

Conclusion Extramedullary plasmacytoma can be the first indication of a plasma cell neoplasm, and its progression to multiple myeloma occurs in up to 30% of cases after the initial diagnosis. Its prognosis is related to the tumor location and lymph node involvement. It should be considered as a differential diagnosis in abdominal tumors.

 

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No conflict of interest has been declared by the author(s).

Publication History

Article published online:
25 April 2025