Concurrent monomorphic epitheliotropic intestinal T-cell lymphoma with aberrant CD20 expression and lung adenocarcinoma: A case report and literature review.

Monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) is a rare and aggressive subtype of intestinal T-cell lymphoma with a dismal prognosis. MEITL with aberrant CD20 expression is even rarer. To date, there have been no reported cases of multiple primary malignant tumors (MPMT) composed of concurrent CD20-positive MEITL and solid tumors. We herein present a case of a 59-year-old female with concurrent small intestinal MEITL with aberrant CD20 expression and lung adenocarcinoma. The patient was admitted to hospital for abdominal pain due to intestinal perforation and underwent partial small intestinal resection. Histopathological examination confirmed MEITL with aberrant CD20 expression of the small intestine without lymph node involvement. Meanwhile, two pulmonary ground-glass opacities (GGOs) were identified and histopathological evaluation confirmed the diagnosis of lung adenocarcinoma. The patient received rituximab-based chemotherapy followed by autologous stem cell transplantation, along with surgical resection for lung adenocarcinoma. She has remained alive for more than 24 months without disease progression. Additionally, we conducted a literature review to enhance clinical awareness of this rare concurrent condition of CD20-positive MEITL and lung adenocarcinoma.