Malignant peritoneal mesothelioma (MPM) is a rare and invasive tumor, and some patients will develop paraneoplastic syndrome (PS) during the course of the disease. This review summarizes PS associated with MPM, focusing on the clinical characteristics and treatment progress in hematological, endocrine, rheumatic, neurological, urinary, and other systems to decrease missed diagnosis and misdiagnosis, help early diagnosis and prompt treatment, and provide guidance for the clinical decision-making of this kind of patients.

Cushing\'s syndrome (CS), as a result of ectopic adrenocorticotropic hormone (ACTH) production, constitutes a common paraneoplastic manifestation of various malignancies, with the most common being small cell lung carcinoma. In the literature, fewer than fifty cases associating ectopic CS with prostate cancer have been documented. In the present study, the case of a 76-year old man suffering from castration-resistant prostate adenocarcinoma that had been treated with enzalutamide and luteinizing hormone-releasing hormone (LHRH) analogue for the last four years is presented. The patient presented to the emergency department with lower extremity muscle weakness, bradypsychia and hypokalemia. Following a thorough diagnostic evaluation, hypercortisolemia was identified. No suppression after low- and high-dose dexamethasone challenge, increased cortisol 24 h excretion and normal pituitary magnetic resonance imaging led to the diagnosis of ectopic CS. Immediate targeted therapy was initiated with adrenal steroidogenesis inhibitors, including metyrapone and ketoconazole along with chemotherapy with docetaxel and prednisolone. There was a remarkable decrease in cortisol levels within days and hospitalization was no longer required. The patient managed to complete three cycles of chemotherapy; unfortunately, he succumbed within three months of the diagnosis of ectopic CS. In the present study, all existing cases of paraneoplastic CS related to prostate cancer are reviewed. The aim of the current study was to highlight the need of early diagnosis and treatment of this entity as it may present with atypical clinical findings and potentially evolve to a life-threatening condition.

BACKGROUND: Nephrotic syndrome (NS) can occur as a paraneoplastic disorder in association with various types of carcinoma. However, paraneoplastic nephrotic syndrome (PNS) is often misdiagnosed as idiopathic nephrotic syndrome or as an adverse effect of oncology treatment, leading to delayed diagnosis and suboptimal treatment. The characteristics of NS associated with solid malignancies are not yet elucidated. We systematically summarized the clinical data for 128 cases of NS combined with solid malignancies with the aim of informing the clinical management of PNS.
METHODS: We searched the PubMed database for articles published from the date of inception through to October 2023 using the following keywords: \"cancer\" or \"malignant neoplasms\" or \"neoplasia\" or \"tumors\" and \"nephrotic syndrome\", \"nephrotic\" or \"syndrome, nephrotic\". All data were extracted from case reports and case series, and the extraction included a method for identifying individual-level patient data.
RESULTS: A literature search yielded 105 cases of PNS and 23 of NS induced by cancer therapy. The median age at diagnosis was 60 years, with a male to female ratio of 1.8:1. In patients with PNS, manifestations of NS occurred before, concomitantly with, or after diagnosis of the tumor (in 36%, 30%, and 34% of cases, respectively). Membranous nephropathy (49%) was the most prevalent renal pathology and found particularly in patients with lung, colorectal, or breast carcinoma. Regardless of whether treatment was for cancer alone or in combination with NS, the likelihood of remission was high.
CONCLUSIONS: The pathological type of NS may be associated with specific malignancies in patients with PNS. Prompt identification of PNS coupled with suitable therapeutic intervention has a significant impact on the outcome for patients.

UNASSIGNED: To describe ocular sarcoid-like reaction as a unique manifestation of paraneoplastic syndrome in the context of concurrent pulmonary sarcoid-like reaction and lung adenocarcinoma.
UNASSIGNED: Single case report and narrative review.
UNASSIGNED: A 59-year-old male patient presented with a year-long history of diminished vision and weight loss. Clinical examination revealed panuveitis and multiple chorioretinal lesions. A CT scan of the chest revealed mediastinal and hilar lymphadenopathy as well as a spiculated right lower lung nodule concerning for malignancy. Subsequent bronchoscopy and biopsy confirmed lung adenocarcinoma and non-caseating granulomas in sentinel lymph nodes.
UNASSIGNED: Although pulmonary granulomatous reaction can be seen in the setting of lung malignancy, and ocular sarcoid-like reaction may present as a paraneoplastic manifestation of systemic malignancy, the presence of concomitant pulmonary and ocular sarcoid-like reactions distinguishes this case. The findings underscore the importance of a systemic workup for patients with concerning constitutional symptoms, as paraneoplastic syndromes and metastatic diseases may mimic uveitis. Recognition of paraneoplastic sarcoidosis as a potential clinical manifestation is essential, especially in patients with chronic illness indicators, necessitating a comprehensive evaluation for malignancy.

Anti-pituitary-specific transcription factor-1 (PIT-1) hypophysitis, a paraneoplastic syndrome resulting from an autoimmune response against PIT-1, typically manifests with undetectable levels of growth hormone (GH) and prolactin (PRL), and significantly low levels of serum thyroid-stimulating hormone (TSH) at diagnosis. These hormonal levels are highly specific to this disease and serve as key diagnostic indicators. Herein, we present a detailed clinical course of a 69-year-old male with a history of gastric cancer and lymph node metastases who developed anti-PIT-1 hypophysitis after the initiation of immune checkpoint inhibitor (ICI) therapy, specifically nivolumab, oxaliplatin, and capecitabine. The patient was referred to our department owing to decreased TSH, free triiodothyronine (T3), and free thyroxine (T4) levels after two doses of nivolumab. Initially suspected as central hypothyroidism due to ICI-related hypophysitis, further assessment confirmed the diagnosis of anti-PIT-1 hypophysitis. Notably, GH, PRL, and TSH levels markedly declined, leading to complete deficiencies 2 months after the first nivolumab dose-a pattern consistent with that of previous cases of anti-PIT-1 hypophysitis. Therefore, this report not only presents an atypical subset of ICI-related hypophysitis but also delineates the process of hormone impairment leading to complete deficiencies in anti-PIT-1 hypophysitis. This case highlights the importance of vigilant monitoring for endocrine issues in patients undergoing ICI therapy, given the escalating incidence of immune-related adverse events associated with the extensive use of ICI therapy for various cancers.

Opsoclonus-myoclonus ataxia syndrome (OMAS), also known as Kinsbourne syndrome, is a rare disorder that presents with myoclonus, ataxia, abnormal eye movements, irritability, and sleep disruptions, often in young children. We report a case of an infant barely 6 months old, with no significant past medical history, who presented to the emergency department with tremors, jerking motions of the head and arms, and rapid eye movements. After an extensive workup, she was found to have a neuroblastoma, which was subsequently surgically removed via thoracotomy. Despite an initial improvement in symptoms post-resection, the patient\'s symptoms recurred. She was subsequently treated with dexamethasone, intravenous immunoglobulin (IVIG), and rituximab. After treatment, the patient was noted to have mild global developmental delays but was otherwise well. This case report highlights the rare occurrence of OMAS in an infant barely 6 months old at diagnosis. Using the PubMed database, a systematic review was conducted to highlight the clinical presentation, diagnosis, and management of OMAS.

Objectives  Ectopic olfactory neuroblastoma is an uncommon manifestation of an already rare neoplasm. We aimed to systematically review the literature for cases of ectopic olfactory neuroblastoma to better characterize this rare disease entity and to present two new case reports. Methods  A search of the PubMed and Embase databases was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to identify English-language articles reporting cases of ectopic olfactory neuroblastoma, published from 1955 through November 2021. Results  Sixty-six cases of ectopic olfactory neuroblastoma were identified in 62 articles including the current review. Ectopic olfactory neuroblastoma arose in a wide age range (2-89 years) without significant sex predilection. It occurred most commonly in the ethmoid (25%), maxillary (25%), and sphenoid (16%) sinuses. Seventy-three percent of cases presented with low Hyams grade (I and II). The most common symptoms were nasal obstruction (32%) and epistaxis (32%). Paraneoplastic syndromes were observed in 27% of patients. The most common treatment was surgical resection followed by adjuvant radiotherapy. Overall, 76% of all patients were disease-free at the time of last follow-up. Locoregional recurrences and distant metastases were found in 19 and 5% of cases, respectively. Conclusion  This systematic review describes previously reported cases of ectopic olfactory neuroblastoma, a disease entity with poorly understood characteristics. Physicians should consider olfactory neuroblastoma in the differential diagnosis for sinonasal masses, as their ectopic presentation may present considerable diagnostic and therapeutic difficulties. Patients with olfactory neuroblastoma may benefit from long-term follow-up and routine endoscopic examinations for surveillance of ectopic recurrences.

Phosphaturic mesenchymal tumors (PMTs) are rare tumors that can cause tumor-induced osteomalacia (TIO) through overproduction of FGF23, a peptide hormone that causes renal phosphate wasting and reduced osteoblastic activity. The diagnosis of PMTs can be difficult to make as the presenting symptoms are non-specific. Although PMT is a rare entity, most cases are benign in nature, not requiring further intervention after surgery, as resection is typically curative. Here, we present a unique case of malignant PMT with de novo liver metastasis in a female patient who presented with TIO and underwent surgical resection of her primary lesion with subsequent regression of her liver metastasis. Moreover, we analyze a review of literature and discuss the importance of a timely diagnosis of this rare phenomenon. It is encouraged that providers strongly consider a diagnosis of PMT in patients with otherwise unexplained bone pain, fatigue, weakness, especially if accompanied with hypophosphatemia. Further studies are also warranted to identify prognostic factors that predict a PMT\'s malignant potential as they may help identify possible therapeutic targets.
Phosphaturic mesenchymal tumor with spread to the liver: A case report and literature review Phosphaturic mesenchymal tumors (PMTs) are rare tumors that can cause bone loss through the excess production of a signal named FGF23. This hormone causes the kidneys to lose phosphate and reduces the body’s ability to build new bone. PMTs are incredibly rare and difficult to diagnose especially since the presenting symptoms can be seen in several different diseases. Although PMT is rare, most cases are benign, only requiring surgery. We are presenting a unique case of a patient who presented with PMT in her right thigh and had evidence that the disease spread to her liver. Our patient underwent surgical resection of her thigh lesion and subsequently had improvement of her liver lesion. In our study, we analyze a review of literature and discuss the importance of a timely diagnosis of this rare phenomenon. It is encouraged that providers strongly consider a diagnosis of PMT in patients with otherwise unexplained bone pain, fatigue, weakness, especially if accompanied by low phosphate levels. Further studies are also warranted to identify prognostic factors that predict a PMT’s malignant potential as they may help identify possible therapeutic targets.

Undifferentiated carcinoma with osteoclast-like giant cells (UC-OGC) is a rare tumor type of pancreatic cancer. Paraneoplastic syndromes, an idiopathic inflammatory myositis characterized by various skin manifestations (such as dermatomyositis (DM)), cannot be attributed to the primary tumor itself. Here, we report an unusual case of UC-OGC presenting as a paraneoplastic syndrome, the first reported from Saudi Arabia and the Arabian Gulf states. A 49-year-old Eritrean woman with known DM was referred to our hospital with a left-sided pleural effusion. Computed tomography of the abdomen revealed a large necrotic splenic mass (~17 × 12.9 × 18.2 cm). The patient underwent exploratory laparotomy with en bloc resection of the mass (splenectomy, distal pancreatectomy, and partial excision of the left hemidiaphragm). Following a histopathological examination of the mass, UG-OGC of the pancreas, presenting as a paraneoplastic syndrome, was diagnosed. To our knowledge, this case is the first to present a paraneoplastic syndrome associated with UC-OGC. The identification of an exceedingly rare tumor presenting atypically as a paraneoplastic syndrome shows the importance of conducting comprehensive examinations of patients with malignancies, emphasizing the need for more reports of similar cases.

Anti-N-methyl-D-aspartate receptor-associated encephalitis (NMDARE) is a rare immune-mediated neuroinflammatory condition characterized by the rapid onset of neuropsychiatric symptoms and autonomic dysfunction. The mechanism of pathogenesis remains incompletely understood, but is thought to be related to antibodies targeting the GluN1 subunit of the NMDA receptor with resultant downstream dysregulation of dopaminergic pathways. Young adults are most frequently affected; the median age at diagnosis is 21 years. There is a strong female predilection with a female sex predominance of 4:1. NMDARE often develops as a paraneoplastic process and is most commonly associated with ovarian teratoma. However, NMDARE has also been described in patients with small cell lung cancer, clear cell renal carcinoma, and other benign and malignant neoplasms. Diagnosis is based on correlation of the clinical presentation, electroencephalography, laboratory studies, and imaging. Computed tomography, positron emission tomography, and magnetic resonance imaging are essential to identify an underlying tumor, exclude clinicopathologic mimics, and predict the likelihood of long-term functional impairment. Nuclear imaging may be of value for prognostication and to assess the response to therapy. Treatment may involve high-dose corticosteroids, intravenous immunoglobulin, and plasma exchange. Herein, we review the hallmark clinicopathologic features and imaging findings of this rare but potentially devastating condition and summarize diagnostic criteria, treatment regimens, and proposed pathogenetic mechanisms.