Paravertebral Pseudoendocrine Sarcoma

Abstract Introduction/Objective Pseudoendocrine sarcoma is a rare and newly described, emerging entity occurring predominantly in middle-aged to elderly males with apredilection for the thoracic paravertebral soft tissue. Pseudoendocrine sarcoma is a recently recognized intermediate-grade sarcoma with CTNNB1 mutations. Methods/Case Report Herein, we present a case of a 66-year-old male with a 10-year history of a progressively enlarging, painful, mid-back lesion. CT scan of the chest demonstrated a right paraspinal soft tissue mass measuring 9.5 x 5.5 x 4.5 cm located at the level of T8-T11. An image-guided biopsy was performed revealing monotonous, epithelioid cells, with round hyperchromatic nuclei, eosinophilic, granular cytoplasm, and indistinct borders arranged in rosettes. Mitoses, necrosis and lymphovascular invasion were not identified.The tumor cells were positive for Beta- catenin, CD56, BCL-2, BCL-6, CD4, CD34 and CD 68, and had a low-proliferative index. The neoplastic cells lacked staining with CK-AE1/AE3, CAM-5.2, NKX3.1, PAX8, Chromogranin, Synaptophysin, NSE, EMA, CD3, CD7, PAX5, and inhibin. The morphology and the immunophenotype support the diagnosis of pseudoendocrine sarcoma. Results (if a Case Study enter NA) N/A. Conclusion To date, few cases have been described in the literature. Recognition of this entity is important due to the potential for local recurrence (43%), and regional and distant metastasis. Complete excision of the lesion as well as adequate patient surveillance is imperative as we gain more understanding of the metastatic potential and prognosis of this emerging entity.