Case Presentation: A 30-year-old morbidly obese woman with a history of Lynch syndrome (hereditary non‐polyposis colorectal cancer), who presented with complaints of lower back pain and subjective fevers. Six months before this presentation she was diagnosed with a large lower paraspinal hematoma treated with embolization and gel foam implantation. Upon presentation, the patient was vitally stable, and the physical exam was significant for tenderness in her right lumbar and iliac regions. Laboratory workup was only pertinent for hemoglobin of 9.5 g/dL. CT scan of the abdomen and pelvis with intravenous contrast showed intermediate attenuation in the right paraspinal region suggestive of a mass with an overlying hematoma. Further imaging with MRI of her lumbar spine showed a 16.3 x 13.2 x 18.4 cm heterogeneous mass along with the right lumbosacral paraspinal musculature, which was concerning for a sarcoma. Additional staging with a CT chest was done, which showed a 7 mm right lower lobe solitary nodule. CT guided biopsy of the paraspinal mass revealed histopathology consistent with a malignant perivascular epithelioid cell neoplasm. Morphologically, tumor cells displayed characteristics of poorly differentiated carcinoma. Further characterization with immunohistochemical staining confirmed epithelial tissue with epithelial membrane antigen (EMA) and desmin (confirming muscle origin), HMB45 and Melan A (confirming melanocytic origin) and smooth muscle actin (SMA) which is compatible with a diagnosis of perivascular epithelioid cell tumor (PEComa). Further staining revealed loss of function of mismatch repair (MMR) proteins MSH2 and MSH6, which was suggestive of Lynch syndrome. Unfortunately, less than 1% of the tumor showed staining associated with programmed death-ligand 1 (PD-L1) immune cell staining, thereby making her a poor candidate for immunotherapy. The patient was subsequently started on neoadjuvant therapy with everolimus (mTOR inhibitor), which she has been tolerating well. She is scheduled to undergo surgical resection of the tumor in the upcoming months.
Discussion: Lynch Syndrome is a rare genetic disorder characterized by an increased occurrence of tumors. This autosomal dominant disease results from mutations in DNA mismatch repair genes, thereby predisposing patients to certain cancers, including colon cancer, endometrial cancer, and ovarian cancer. Rarely do sarcomas occur as a part of this syndrome. PEComas, a subset of sarcomas, are mesenchymal tumors composed of distinctive perivascular epithelioid cells. Mismatch repair protein deficiency is not a common characteristic amongst these sarcomas. In one study, only seven cases (2.3%) out of 447 were found to have microsatellite instability of this type, and only one of which had a diagnosis of Lynch syndrome.
Conclusions: PEComas are neoplasms with perivascular epithelioid cell differentiation. Very few cases of Lynch syndrome predisposing to PEComa described in the literature. Furthermore, this patient received treatment with an mTOR inhibitor, which supports the promising role of this treatment option for this unusual presentation of Lynch Syndrome..