Clinical Features of Cutaneous Paraneoplastic Syndromes in Hodgkin Lymphoma.

Cutaneous paraneoplastic syndromes due to Hodgkin lymphoma present with a wide spectrum of clinical manifestations from generalized pruritus to exfoliative erythroderma. We summarize the clinical findings and outcomes of 14 patients with Hodgkin lymphoma and associated cutaneous paraneoplastic syndromes treated at Mayo Clinic over the past 3 decades. Cutaneous paraneoplastic syndromes may be present at the time of lymphoma diagnosis, whereas in other patients, it may appear at the time of relapse, including patients with initial absence of cutaneous manifestations during the initial lymphoma presentation. Our results indicate that complete resolution of the paraneoplastic syndrome is associated with significantly improved overall survival. Recognition of cutaneous paraneoplastic syndromes is a crucial surrogate of relapsed malignancy and treatment requires targeting the underlying malignancy.

Digital Gangrene as a Paraneoplastic Manifestation of Peripheral T-cell Lymphoma Not Otherwise Specified Type.

BACKGROUND: Peripheral T cell lymphoma (PTCL), not otherwise specified (NOS) is a heterogenous group of predominantly nodal T cell lymphomas that generally presents with lymphadenopathy with or without extra nodal involvement. Acral vascular syndrome clinically presents as digital ischemia with Raynaud's phenomenon and acral cyanosis. Although, this condition is commonly associated with connective tissue disorder, smoking and vasculitis, its association with lymphoid malignancy is very rare. Here, we present a case report of a patient with digital gangrene of all toes and fingers as a presenting symptom of PTCL-NOS. CASE DESCRIPTION: A 62 year old male presented with digital ischemia associated with pain, low grade fever, loss of appetite and significant weight loss of 6 kilograms over a period of 3 months. On examination, he was found to have bilateral inguinal and axillary lymph nodes with gangrenous changes over toes and fingers but peripheral pulses were palpable. On evaluation he had anemia, elevated ESR and CRP. CT angiogram revealed thinned out digital arteries with multifocal areas of narrowing. Patient was screened for other causes of digital gangrene and was tested negative for ANCA, ANA, cryoglobulins and viral markers. Lymph node biopsy with IHC was suggestive of peripheral T-cell lymphoma-NOS and was started on CHOP regimen. Lymph nodes size decreased and gangrenous changes resolved. CONCLUSION: Though digital ischemia is a rare paraneoplastic presentation of lymphoma, it should be considered if there is a rapid progression of gangrene. Early initiation of chemotherapy may result in the reduction of further progression of digital gangrene and thus prevent permanent disability. In our patient, progression of gangrene was prevented even though it was an aggressive variant of T cell lymphoma.

Phosphaturic mesenchymal tumor-induced bilateral osteomalacia femoral neck fractures: a case report.

Phosphaturic mesenchymal tumors (PMT) are rare and distinctive tumors that typically result in paraneoplastic syndrome known as tumor-induced osteomalacia (TIO). We report a case of bilateral osteoporotic femoral neck fracture caused by PMT. PMT was surgically resected, followed by sequential treatment of bilateral femoral neck fractures with total hip arthroplasty (THA). A 49-year-old perimenopausal woman experienced consistent bone pain with limb weakness persisting for over 2 years. Initially, she was diagnosed with early osteonecrosis of the femoral head and received nonsurgical treatment. However, from 2020 to 2022, her pain extended to the bilateral shoulders and knees with increased intensity. She had no positive family history or any other genetic diseases, and her menstrual cycles were regular. Physical examination revealed tenderness at the midpoints of the bilateral groin and restricted bilateral hip range of motion, with grade 3/5 muscle strength in both lower extremities. Laboratory findings revealed moderate anemia (hemoglobin 66 g/L), leukopenia (2.70 × 109/L), neutropenia (1.28 × 109/L), hypophosphatemia (0.36 mmol/L), high alkaline phosphatase activity (308.00 U/L), and normal serum calcium (2.22 mmol/L). After surgery, additional examinations were performed to explore the cause of hypophosphatemic osteomalacia. After definitive diagnosis, the patient underwent tumor resection via T11 laminectomy on August 6, 2022. Six months after the second THA, the patient regained normal gait with satisfactory hip movement function without recurrence of PMT-associated osteomalacia or prosthesis loosening. By providing detailed clinical data and a diagnostic and treatment approach, we aimed to improve the clinical understanding of femoral neck fractures caused by TIO.

Tumour-induced osteomalacia: the long road to diagnosis and recovery.

Tumour-induced osteomalacia is caused by tumorous production of fibroblast growth factor 23 (FGF23) leading to urinary phosphate wasting, hypophosphataemia and decreased vitamin D activation. The resulting osteomalacia presents with muscle weakness and bone pain but progresses to multiple pathological fractures. Patients often remain undiagnosed for years with severe physical, psychological and economic ramifications. A young woman presented with multiple spontaneous fractures including bilateral femoral fractures. Laboratory tests revealed severe hypophosphataemia, elevated bone turnover markers and low to normal calcium and 25-hydroxy-vitamin D levels. Treatment with phosphate, alfalcalcidol, calcium and magnesium was initiated. 68Gallium-DOTATOC positron emission tomography imaging revealed a mass in the right foot and venous sampling of FGF23 from all extremities confirmed this tumour as the culprit. Biopsy and histology were consistent with a phosphaturic mesenchymal tumour, which was surgically resected. Phosphate levels quickly normalised postoperatively but a long convalescence with hungry bone syndrome, fracture healing and physical therapy followed.

Thymic carcinoma presenting with overlap polyarthritis and myositis: A rare paraneoplastic syndrome in childhood.

Thymic tumors are very rare neoplasms in children and account for less than 1% of mediastinal tumors in pediatric patients. One-third of the pediatric patients present with symptoms related to the compression of the tumor mass on the surrounding anatomic structures, and paraneoplastic syndromes such as myasthenia gravis, pure red cell aplasia, acquired hypogammaglobulinemia, and connective tissue disorders, which rarely occur in children with thymic tumors. Herein, we report a case of thymic carcinoma mimicking the symptoms of a connective tissue disease with symmetrical polyarthritis accompanying myositis, fever, weight loss, and malaise in a 15-year-old male patient. To our knowledge, this is the first case pediatric thymic carcinoma accompany with severe polyarthritis and myopathy, thus we have reviewed the current literature regarding the cases of thymic malignancies coexisting with paraneoplastic syndromes in children.

Successful Superficial Blood Sampling to Localize a Fibroblast Growth Factor-23-Producing Tumor.

BACKGROUND Tumor-induced osteomalacia (TIO) is a paraneoplastic syndrome caused by aberrant fibroblast growth factor-23 (FGF-23)-producing tumors. Early surgical resection is the optimal strategy for preventing TIO progression. Thus, tumor localization is a priority for successful treatment. A simple and safe examination method to identify functional endocrine tumors is essential to achieve better outcomes in patients with TIO. CASE REPORT A 64-year-old Japanese man with recurrent fractures, hypophosphatemia, and elevated alkaline phosphatase and FGF-23 levels (109 pg/mL) was admitted to our university hospital and was diagnosed with FGF23-related hypophosphatemic osteomalacia. Notably, the superficial dorsal vein in the patient's left foot exhibited a high FGF-23 level (7510 pg/mL). Octreotide and ¹8F-fluorodeoxyglucose (FDG) scintigraphy and systemic venous sampling revealed that the tumor in the third basal phalanx of the left foot was responsible for FGF-23 overproduction. Tumor resection resulted in a rapid decrease in serum FGF-23 levels and an increase in serum phosphorus levels. CONCLUSIONS Octreotide scintigraphy, FDG-positron emission tomography, and systemic venous sampling are the standard methods for localizing functional endocrine tumors. However, the limited availability and invasive nature of these examinations hinder effective treatment. Here, we highlight the importance of peripheral superficial blood sampling as an alternative to conventional systemic methods for confirming the presence of FGF-23-producing tumors. Clinicians should consider TIO as a potential cause of acquired hypophosphatemic osteomalacia. Furthermore, peripheral superficial vein blood sampling may be useful for confirming the localization of FGF-23-producing tumors.

Paraneoplastic Syndromes in Hepatocellular Carcinoma, Epidemiology, and Survival: A Retrospective Seven Years Study.

Background and Objectives: Liver cancer poses a significant global health threat, ranking among the top three causes of cancer-related deaths. Patients with hepatocellular carcinoma (HCC) often present with symptoms associated with neoplasms or unusual clinical features such as paraneoplastic syndromes (PNS), including hypoglycemia, hypercholesterolemia, thrombocytosis, and erythrocytosis. Our study aimed to investigate the prevalence, clinical characteristics, and survival outcomes associated with PNS in HCC patients and assess each PNS's impact on patient survival. Materials and Methods: We conducted a retrospective analysis of PNS clinical features and survival among consecutive HCC patients diagnosed at our department over seven years, comparing them with HCC patients without PNS. The study involved a retrospective data evaluation from 378 patients diagnosed with HCC between January 2016 and October 2023. Results: We obtained a PNS prevalence of 25.7%, with paraneoplastic hypercholesterolemia at 10.9%, hypoglycemia at 6.9%, erythrocytosis at 4.5%, and thrombocytosis at 3.4%. Patients with PNS tended to be younger and predominantly male. Multivariate analysis revealed a strong correlation between PNS and levels of alpha-fetoprotein and tumor size, with diabetes also showing a significant statistical association (p < 0.05). Subgroup analysis based on specific paraneoplastic syndromes demonstrated shorter survival in patients with PNS, albeit without significant statistical differences, except for hypoglycemia (p < 0.0001). Matched analysis indicated a shorter survival rate for patients with PNS, although no significant statistical differences were observed. Conclusions: PNS are frequently observed in HCC cases and are associated with unfavorable prognoses and decreased survival rates due to their correlation with increased tumor burdens. However, they do not independently predict poor survival. The impact of individual PNS on HCC prognosis varies.

Membranous Nephropathy as a Paraneoplastic Syndrome in Cancer of Unknown Primary.

BACKGROUND/AIM: Membranous nephropathy (MN) is a nephrotic syndrome with both idiopathic and secondary etiologies. The mechanism of cancer-associated MN is presumed to involve the immunological production of antibodies against a tumor antigen, although little is known about the detailed mechanism. Lung cancer is a major neoplasm associated with cancer-associated MN. However, the simultaneous occurrence of secondary MN in patients with cancer of unknown primary (CUP) remains unclear. CASE REPORT: Here, we present a case of secondary MN in a 72-year-old female as a paraneoplastic syndrome in CUP. Thoracic radiotherapy up to a total of 60 Gy was initially performed on the right subclavian and mediastinal lymph nodes. Computed tomography revealed marked shrinking of these lymph nodes, and the secondary MN also improved without any symptoms. CONCLUSION: The presence of proteinuria in patients with CUP suggests the possibility of secondary MN as a rare differential diagnosis.

Clinical outcomes and safety of immune checkpoint inhibitors in patients with solid tumors and paraneoplastic syndromes.

BACKGROUND: Patients with paraneoplastic syndromes (PNS) are excluded from clinical trials involving immune checkpoint inhibitors (ICIs) due to safety concerns. Moreover, real-world data on efficacy and safety is scarce. METHODS: In this retrospective study, data were collected on patients with PNS and solid tumors receiving ICI between 2015 and 2022 at nine institutions. Patients were classified into: Cohort 1 (pre-existing PNS before ICI initiation), cohort 2 (PNS during ICI treatment), and cohort 3 (PNS after ICI discontinuation). Patients with metastatic non-small cell lung cancer (NSCLC) (mNSCLC) from cohort 1 were matched to patients who were PNS-free at each institution up to a 1:3 ratio for age, sex, type of ICI, use of concurrent chemotherapy, and number of lines of systemic therapy prior to ICI initiation. Kaplan-Meier method was used to assess overall survival (OS) and time-to-next treatment (TTNT). RESULTS: Among 109 patients with PNS treated with ICIs, median age at ICI initiation was 67 years (IQR: 58-74). The most represented cancer type was NSCLC (n=39, 36%). In cohort 1 (n=55), PNS exacerbations occurred in 16 (29%) patients with median time to exacerbation after ICI of 1.1 months (IQR: 0.7-3.3). Exacerbation or de novo PNS prompted temporary/permanent interruption of ICIs in 14 (13%) patients. For cohort 2 (n=16), median time between ICI initiation and de novo PNS was 1.2 months (IQR: 0.4-3.5). Treatment-related adverse events (trAEs) occurred in 43 (39%) patients. Grade ≥3 trAEs occurred in 18 (17%) patients. PNS-directed immunosuppressive therapy was required in 55 (50%) patients. We matched 18 patients with mNSCLC and PNS (cohort 1) to 40 without PNS, treated with ICIs. There was no significant difference in OS or TTNT between patients with mNSCLC with and without PNS, although a trend was seen towards worse outcomes in patients with PNS. TrAEs occurred in 6/18 (33%) and 14/40 (35%), respectively. Grade ≥3 trAEs occurred in 4 (22%) patients with PNS and 7 (18%) patients without PNS. CONCLUSIONS: Exacerbations of pre-existing PNS occurred in 29% of patients treated with ICIs and both exacerbations and de novo PNS occur early in the ICI course. TrAE from ICIs were similar between patients with and without PNS. Our data suggest that pre-existing PNS should not preclude consideration of ICI therapy although patients may not derive the same clinical benefit compared with patients without PNS.

Seroprevalence of neuronal antibodies in diseases mimicking autoimmune encephalitis.

Detection of neuronal antibodies for autoimmune encephalitis and paraneoplastic neurological syndromes relies on commercially available cell-based assays and lineblots. However, lineblots may reveal the presence of neuronal antibodies in patients with various non-autoimmune etiologies. Herein we describe patients with non-autoimmune etiologies (cohort B) and detectable neuronal antibodies and compare them to definite cases of autoimmune encephalitis (cohort A) for differences in clinical data. All patients positive for at least one neuronal antibody were retrospectively evaluated for autoimmune encephalitis and/or paraneoplastic neurological syndrome between 2016 and 2022. 39 cases in cohort B and 23 in cohort A were identified. In cohort B, most common diagnoses were neurodegenerative disorders in 9/39 (23.1%), brain tumors in 6/39 (15.4%) while most common detected antibodies were anti-titin (N10), anti-recoverin (N11), anti-Yo (N8) and all were detected in serum only. Differential aspects between cohort A and B were CSF pleocytosis (14/23 (60.8%) vs 11/35 (31.4%), p = 0.042, respectively), MRI features suggestive of encephalitis (6/23 (26.1%) vs 0 (0%), p = 0.002, respectively) and epilepsy restricted to temporal lobes (14/23 (60.9%) vs 2/30 (6.7%), p = 0.0003, respectively). A large proportion of lineblot results were non-specific when only serum was tested and were frequently found in non-autoimmune neurological conditions.

Paraneoplastic neurologic manifestations of neuroendocrine tumors.

Neuroendocrine neoplasms (NENs) are a heterogeneous group of tumors arising from the transformation of neuroendocrine cells in several organs, most notably the gastro-entero-pancreatic system and respiratory tract. The classification was recently revised in the 5th Edition of the WHO Classification of Endocrine and Neuroendocrine Tumors. NENs can rarely spread to the central or peripheral nervous systems. Neurologic involvement is determined by the rare development of paraneoplastic syndromes, which are remote effects of cancer. Mechanisms depend on immunologic response to a tumor, leading to the immune attack on the nervous system or the production of biologically active ("functioning") substances, which can determine humoral (endocrine) effects with neurologic manifestations. Paraneoplastic neurologic syndromes (PNS) are immunologically mediated and frequently detected in small cell lung cancer but rarely seen in other forms of NEN. PNS and Merkel cell carcinoma is increasingly reported, especially with Lambert Eaton myasthenic syndrome. Endocrine manifestations are found in a wide spectrum of NENs. They can develop at any stage of the diseases and determine neurologic manifestations. Patient outcomes are influenced by tumor prognosis, neurologic complications, and the severity of endocrine effects.

Overview of treatment strategies in paraneoplastic neurological syndromes.

Treatment strategies in paraneoplastic neurological syndromes rely on the three pillars of tumor treatment, immunotherapy, and symptomatic treatment, the first one being by far the most important in the majority of patients and syndromes. Classically, antibodies against extracellular antigens are directly pathogenic, and patients with these syndromes are more responsive to immunomodulatory or immunosuppressive treatments than the ones with antibodies against intracellular targets. This chapter first discusses some general principles of tumor treatment and immunotherapy, followed by a closer look at specific treatment options for different clinical syndromes, focusing on symptomatic treatments.

The association between paraneoplastic neurological syndromes (PNS) and urothelial carcinoma - A review of the literature.

Paraneoplastic neurological syndromes (PNS) are rare neurological disorders arising from malignancy-triggered autoimmunity, yet their association with urothelial carcinoma remains unclear. This systematic review intends to explore any connection, alongside patient/clinical features and management. A literature search identified 25 cases of bladder and upper tract carcinoma linked to PNS. Overall, while infrequent, a meaningful association between PNS and urothelial carcinoma was found in that 84% of cases met a 'possible'-or-'higher-likelihood' PNS diagnosis. Most cases presented with high-risk PNS phenotypes, predominantly cerebellar syndromes and encephalomyelitis/sensory neuronopathy, ∼17 months within cancer diagnosis/recurrence. Review findings suggest a female preponderance in suspected PNS despite higher male incidence of urothelial cancer. Main treatments consisted of surgery alongside chemotherapy or immunotherapeutics (IVIG and/or corticosteroids), which improved symptoms for a slight majority (60%). Ultimately, while common PNS-associated neoplasms should always first be excluded in suspected PNS, in the absence of alternative causes, urothelial carcinomas do merit clinical consideration.

Paraneoplastic Syndromes in Neuroendocrine Prostate Cancer: A Systematic Review.

Neuroendocrine prostate cancer (NEPC) is a rare subtype of prostate cancer (PCa) that usually results in poor clinical outcomes and may be accompanied by paraneoplastic syndromes (PNS). NEPC is becoming more frequent. It can initially manifest as PNS, complicating diagnosis. Therefore, we reviewed the literature on the different PNS associated with NEPC. We systematically reviewed English-language articles from January 2017 to September 2023, identifying 17 studies meeting PRISMA guidelines for NEPC and associated PNS. A total of 17 articles were included in the review. Among these, Cushing's Syndrome (CS) due to ectopic Adrenocorticotropic hormone (ACTH) secretion was the most commonly reported PNS. Other PNS included syndrome of inappropriate Anti-Diuretic Hormone secretion (SIADH), Anti-Hu-mediated chronic intestinal pseudo-obstruction (CIPO), limbic encephalitis, Evans Syndrome, hypercalcemia, dermatomyositis, and polycythemia. Many patients had a history of prostate adenocarcinoma treated with androgen deprivation therapy (ADT) before neuroendocrine features developed. The mean age was 65.5 years, with a maximum survival of 9 months post-diagnosis. NEPC is becoming an increasingly more common subtype of PCa that can result in various PNS. This makes the diagnosis and treatment of NEPC challenging. Further research is crucial to understanding these syndromes and developing standardized, targeted treatments to improve patient survival.

Tumor-induced Osteomalacia Successfully Treated by En Bloc Tumor Excision and Reconstruction Using a Tumor-bearing Frozen Autograft: A Case Report.

BACKGROUND/AIM: Tumor-induced osteomalacia (TIO) is a rare pathology caused by overproduction of fibroblast growth factor 23 (FGF23). Its common clinical features include generalized muscle weakness, bone pain, and fractures. Complete resection of the offending tumor is the mainstay treatment. In this report, we present the first case of TIO by an FGF23 producing tumor treated using a tumor-bearing autograft treated with liquid nitrogen. CASE REPORT: A 63-year old female presented with generalized body pain, particularly in the left arm. The patient was diagnosed with a FGF23 producing tumor of the left humerus. Wide resection of the involved tumor was performed using a tumor-bearing autograft that was treated with liquid nitrogen. Postoperatively, the FGF23 and alkaline phosphatase (ALP) levels significantly decreased and inorganic phosphate normalized. There was also subsequent relief of generalized body pain. Immediately after the operation, range of motion of the left shoulder and elbow was initiated. The patient was instructed to perform forward flexion and abduction up to 90° with a rotational restraint. Almost complete bone union was observed at 12 months post procedure. Postoperative functional results were as follows: Musculoskeletal Tumor Society (MSTS) score of 27/30, 90% and International Society of Limb Salvage (ISOLS) score of 26/30, 87%. Ten years after the surgery, osteotomy line was completely obscured based on radiographs. The patient was disease free and without activity limitation. CONCLUSION: This is the first case report of wide excision of a FGF23 producing tumor and reconstruction using a tumor-bearing frozen autograft performed with excellent outcomes.

Approaching virtual osteoid volume estimation and in-depth tissue characterization in patients with tumor-induced osteomalacia.

Tumor-induced osteomalacia (TIO) poses a significant diagnostic challenge, leading to increased disease duration and patient burden also by missing clinical suspicion. Today, diagnosis of osteomalacia relies on invasive iliac crest biopsy, if needed. Therefore, a noninvasive method would be beneficial for patients with severe osteomalacia, such as TIO, to inform their clinical management and address specific needs, like estimating the regeneration capacity at high osteoid volumes (OVs) or the potential of a hungry bone syndrome after tumor removal. Furthermore, given the lack of comprehensive histological characterization of TIO, there is a need for additional tissue characterization. Therefore, our assessment encompassed iliac crest biopsies that were examined using quantitative electron backscattered microscopy, Raman spectroscopy, micro-computed tomography, and histology to analyze the biopsy tissue. Our clinical assessment encompassed DXA and high-resolution peripheral quantitative computed tomography (HR-pQCT) alongside with biochemical analyses and clinical evaluations. Combining imaging and clinical data, we established a model to predict the OV. We compared 9 TIO patients with 10 osteoporosis (OPO) patients and 10 healthy controls. Histological analyses confirmed a pronounced OV in TIO patients (OPO: 1.20% ± 1.23% vs TIO: 23.55% ± 12.23%, P < .0005), and spectroscopy revealed lower phosphate levels in TIO biopsies. By combining HR-pQCT and laboratory diagnostics, we developed a linear regression model to noninvasively predict the OV revealing significantly higher modeled OV/BVmodel values of 24.46% ± 14.22% for TIO compared to the control group (5.952% ± 3.44%, P ≤ .001). By combining laboratory diagnostics, namely, ALP and Tt.BMDRadius measured by HR-pQCT, we achieved the calculation of the virtual osteoid volume to bone volume ratio (OV/BVmodel) with a significant correlation to histology as well as reliable identification of TIO patients compared to OPO and control. This novel approach is potentially helpful for predicting OV by noninvasive techniques in diagnostic procedures and improving the clinical management of TIO.

Osteomalacia, a bone mineralization disease, results in soft bones due to a lack of calcium or phosphate. Tumor-induced osteomalacia (TIO) is an acquired and challenging form of osteomalacia due to low serum phosphate levels that often lead to prolonged patient suffering. Current diagnosis of osteomalacia involves surgical bone biopsies, but a noninvasive approach would be beneficial, improving clinical management and addressing specific needs like estimating the bone's quality and ability to recover. We used advanced techniques like electron microscopy, spectroscopy, and high-resolution CT to study bone samples from 9 TIO patients. Additionally, we assessed their bone health through sophisticated imaging and blood analyses. Microscopy confirmed huge amounts of soft bone tissue due to a severe mineralization defect. By combining imaging and blood analysis, we developed a noninvasive method to predict the amount of soft tissue (osteoid) to understand soft bones without the need for surgical interventions. In conclusion, our innovative approach, combining blood diagnostics (alkaline phosphatase) with total BMD from high-resolution 3D clinical imaging of the lower arm, allows us to predict the osteoid amount virtually. This method can also compare TIO patients with controls or those with osteoporosis and might be helpful in the future.

Acquired Forms of Fibroblast Growth Factor 23-Related Hypophosphatemic Osteomalacia.

Fibroblast growth factor 23 (FGF23) is a pivotal humoral factor for the regulation of serum phosphate levels and was first identified in patients with autosomal dominant hypophosphatemic rickets and tumor-induced osteomalacia (TIO), the most common form of acquired FGF23-related hypophosphatemic rickets/osteomalacia (FGF23rHR). After the identification of FGF23, many other inherited and acquired forms of FGF23rHR were reported. In this review article, the detailed features of each acquired FGF23rHR are discussed, including TIO, ectopic FGF23 syndrome with malignancy, fibrous dysplasia/McCune-Albright syndrome, Schimmelpenning-Feuerstein-Mims syndrome/cutaneous skeletal hypophosphatemia syndrome, intravenous iron preparation-induced FGF23rHR, alcohol consumption-induced FGF23rHR, and post-kidney transplantation hypophosphatemia. Then, an approach for the differential diagnosis and therapeutic options for each disorder are concisely introduced. Currently, the majority of endocrinologists might only consider TIO when encountering patients with acquired FGF23rHR; an adequate differential diagnosis can reduce medical costs and invasive procedures such as positron emission tomography/computed tomography and venous sampling to identify FGF23-producing tumors. Furthermore, some acquired FGF23rHRs, such as intravenous iron preparation/alcohol consumption-induced FGF23rHR, require only cessation of drugs or alcohol to achieve full recovery from osteomalacia.

Mechanistic characterization of a Drosophila model of paraneoplastic nephrotic syndrome.

Paraneoplastic syndromes occur in cancer patients and originate from dysfunction of organs at a distance from the tumor or its metastasis. A wide range of organs can be affected in paraneoplastic syndromes; however, the pathological mechanisms by which tumors influence host organs are poorly understood. Recent studies in the fly uncovered that tumor secreted factors target host organs, leading to pathological effects. In this study, using a Drosophila gut tumor model, we characterize a mechanism of tumor-induced kidney dysfunction. Specifically, we find that Pvf1, a PDGF/VEGF signaling ligand, secreted by gut tumors activates the PvR/JNK/Jra signaling pathway in the principal cells of the kidney, leading to mis-expression of renal genes and paraneoplastic renal syndrome-like phenotypes. Our study describes an important mechanism by which gut tumors perturb the function of the kidney, which might be of clinical relevance for the treatment of paraneoplastic syndromes.

A 50-Year-Old Man Presenting with Multiple Bone Lesions and a Diagnosis of Phosphaturic Mesenchymal Tumor of the Femur.

BACKGROUND Phosphaturic mesenchymal tumor (PMT) is an extremely rare mesenchymal neoplasm that is commonly seen in bone and soft tissue. It is associated with a paraneoplastic syndrome, oncogenic osteomalacia, due to tumor-induced urinary phosphate wasting. It is demonstrated to be predominantly mediated by fibroblast growth factor 23 (FGF23)/fibroblast growth factor receptor 1 (FGFR1) axis. Clinically, PMT usually presents as a solitary lesion in the bone. The diagnosis of PMT is challenging due to its non-specific clinical manifestation, radiologic findings, and morphological features. CASE REPORT We report the case of a 50-year-old man presenting with multiple lytic bone lesions and associated pathologic fracture of the right femur, clinically suspicious for multiple myeloma or other metastatic malignant process. Resection from the right femur showed a hypercellular lesion composed of oval-to-spindled cells infiltrating the native trabecular bone with admixed multinucleated giant cells. Immunohistochemical (IHC) staining and in situ hybridization (ISH) demonstrated the tumor cells were positive for SATB2, ERG, FGFR1, and FGF23 ISH. DNA and RNA next-generation sequencing showed marked increases in mRNA levels of FGF23 and FGFR1. The constellation of clinicoradiologic, histomorphologic, IHC, and molecular findings supported a diagnosis of primary benign PMT. CONCLUSIONS This case report discusses a patient with PMT presenting with multifocal lesions due to tumor-induced osteomalacia at initial presentation. We hope that this report will increase the awareness of clinician and pathologists of PMT as a differential diagnosis in patients presenting with multifocal lytic bone lesions. In turn, this will prevent misdiagnosis and overtreatment of a typically benign process.