TFE3-expressing primary perivascular epithelioid cell tumor of the Lymph node mimicking nodal relapse of rectal cancer: A case report

Introduction: Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm. Presentation of case: We treated a 50-year-old woman who underwent neoadjuvant chemoradiotherapy followed by low anterior resection and adjuvant chemotherapy for ystage IIIB rectal adenocarcinoma. The patient was diagnosed with metastatic rectal adenocarcinoma in the right lower lobe of the lung after 14 months of follow-up. Later, after 3 years of follow-up, a mass in the gastrosplenic area was revealed by computed tomography, which was considered indicative of metachronous mass relapse. The patient underwent partial omentectomy, and an enlarged mass measuring 2.2 × 1.3 cm was found. Microscopic findings revealed an alveolar-like collection of epithelioid cells surrounded by a thin-wall vascular channel within a lymph node (LN). These epithelioid cells were positive for HMB45 and TFE3 but negative for Melan-A, CK, and S100. The patient was finally diagnosed with TFE3-expressing primary PEComa of LN. Discussion: We report a rare case of TFE3-expressing primary LN PEComa that mimicked nodal recurrence of rectal cancer. Thus, imaging results in patients affected by neoplasm present a clinical diagnostic dilemma, as the presence of newly onset PEComa of LN may lead to the erroneous diagnosis of tumor recurrence or progression. Conclusion: Suspicious isolated recurrences of rectal cancer in unusual locations may require surgical excision to confirm definitive diagnosis.