Introduction: Schwannomas (Schs) are benign tumor masses that rarely occur intra-abdominally and rarely reach larger diameters. When present, they occur as rare solitary nerve sheath tumors of peri-neural Schwann cells. Schwannoma mostly affects the nerves of the extremities, trunk, or the head and neck region. They are more common in female patients, mostly among patients between the third and fifth decade. They occur spontaneously but could also be found in association with a group of genetic autosomal dominant disorders called type 2. When present intra-abdominally, schwannomas grow slowly without significant clinical signs and symptoms. Clinical importance is presented in cases of occupying intra-abdominal space and impingement of surrounding structures, which causes intermittent pain. Only 0.5–5% of all retroperitoneal tumors are schwannomas and their malignant transformation is very rare. Case report: The authors present a case of a large intra-abdominal schwannoma in a 70-year-old female patient. She underwent CT scanning due to refractory left-sided subcostal pain, which revealed a large tumor mass in the left-sided hemiabdomen. Preoperative cytologic biopsy confirmed Sch. The patient underwent an MRI scan upon admission to our department, which revealed the origin of the tumor at the left-sided L3 level and intra-abdominal tumor spreading with the largest diameter of 25 cm. The patient underwent multidisciplinary surgical excision, confirmed by MRI scan in a period of five months postoperatively. Conclusions: Its rare presentation leads to the necessity to adequately evaluate such patients, especially to avoid any hidden diagnosis which might lead to further complications. The goal of a multidisciplinary approach should be emphasized as maintaining a good postsurgical condition without neurological deficits.

Background/Objectives: Given the rising prevalence of autoimmune diseases and the need for new insights into the pathology of these disorders, it is important to summarize current knowledge, with an emphasis on Hashimoto’s thyroiditis (HT), since it is especially on the rise. Hypoxia is part of various pathophysiological conditions, and hypoxia-inducible factor (HIF) is a key factor in these processes. Hypoxia is involved in the regulation of hormones and the development of endocrine disorders. With this in mind, this narrative review summarizes the current state of knowledge on the relationship between autoimmune diseases, focusing on HT and the effects of hypoxia through the role of HIF. Methods: Multiple databases such as PubMed, NIH, Scopus, Web of Science, ScienceDirect, and Google Scholar were thoroughly searched for relevant keyword. Results: In HT, thyrocyte-derived reactive oxygen species and chronic lymphocytic infiltration stabilize HIF-1α, tilting CD4+ T cell polarity towards Th17 and away from regulatory T cells. Increased levels of Mammalian target of rapamycin (mTOR)/HIF-1α and reduced Sirtuin 1 (SIRT1) in T cells from patients diagnosed with HT confirm this metabolic skew. Furthermore, the data position HIF-1α as a therapeutic target. Inhibitors of mTOR or agents that restore SIRT1 could complement levothyroxine and antioxidant strategies. Hypoxia and the HIF signaling pathway have a role in energy homeostasis through various ways, for example, via metabolic effects of thyroid hormones, which are associated with the clinical manifestations of HT. Conclusions: Elucidation of HIF-1α-centered gene networks and testing of HIF-targeted interventions may curb the growing clinical burden of HT.