A 56-year-old man presented with weight loss, abdominal pain, and altered bowel habits. Computed tomography revealed an appendiceal mass with hepatic lesions and regional lymphadenopathy, suggestive of advanced appendiceal malignancy. Surgical exploration identified a mucin-producing appendiceal tumor with metastatic involvement of the mesentery, liver, and lymph nodes. Histopathological examination confirmed an invasive, moderately differentiated mucinous adenocarcinoma of the appendix, without lymphovascular or perineural invasion. The mesenteric lesion showed malignant neoplastic cells consistent with metastatic appendiceal adenocarcinoma, infiltrating the surrounding tissue. The patient underwent surgical resection followed by systemic chemotherapy. During follow-up, clinical evolution was consistent with advanced metastatic disease requiring ongoing multidisciplinary management. This case highlights the diagnostic and therapeutic challenges of advanced appendiceal mucinous adenocarcinoma and emphasizes the importance of complete pathological characterization and coordinated oncologic care.

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive lymphoma with a poor prognosis. The human T-lymphotropic virus 1 (HTLV-1) is associated with immunodeficiency and increased extranodal involvement in patients with diffuse large B-cell lymphoma (DLBCL). We report on a 47-year-old woman with spastic paraparesis and hepatitis B who was diagnosed with the acute form of ATLL. The clinical picture reveals peripheral generalized lymphadenopathy and splenomegaly. Findings on a hematologic exam indicated leukocytosis with lymphocytosis. A bone marrow biopsy/aspiration confirmed 50% T-cell lymphoid infiltration. Biochemistry results revealed hypercalcemia and a high lactate dehydrogenase value. Results of a CT scan indicated abdominal and thoracic adenopathy as well as moderate splenomegaly. A supraclavicular lymph node biopsy established a DLBCL diagnosis. The final diagnosis was composite lymphoma, DLBCL, and ATLL. The CHOP (cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate [Oncovin], and prednisone) regimen was chosen due to the patient's ECOG performance status. Multiple infectious complications were diagnosed during chemotherapy-induced secondary aplasia. A complete remission, confirmed via PET-CT imaging, was obtained. After 1 month, a skin tumor on the upper right thigh was discovered and biopsied, and the histopathological exam and immunochemistry findings indicated Epstein-Barr virus-DLBCL lymphoma. The association of 2 aggressive lymphomas in a single HTLV-1 carrier is a rare report, and the evolution was severe, complicated by opportunistic infections, and unfavorable.

Paraneoplastic neurological syndromes (PNS) are an uncommon complication of malignancy, characterized by autoantibody generation against neuronal structures, causing a spectrum of neurological syndromes affecting the central, peripheral, and/or autonomic nervous systems. PNS in lymphoma is exceedingly rare and there is limited evidence on the features, incidence, and severity of these neurological sequelae secondary to malignancy. Here, we report on a case of isolated diffuse motor neuropathy secondary to underlying nodular-sclerosis classical Hodgkin's lymphoma (cHL) in a 71-year-old male. This patient initially presented to the hospital with 3 months of progressive generalized weakness, weight loss, gait instability, and a rash. A broad workup revealed evidence of diffuse lymphadenopathy, which was characterized as nodular-sclerosis cHL on biopsy. Concurrent neurological workup demonstrated generalized axonal motor neuropathy on nerve conduction studies with negative serologies for a panel of paraneoplastic autoantibodies, but positive Asialo-GM1 titers, a marker of autoimmune myopathy. The patient was initiated on doxorubicin, vinblastine, and dacarbazine (AVD) for their lymphoma and received two doses of IVIg for their motor neuropathy, which did not reoccur. The patient was transitioned to brentuximab + nivolumab for 4 cycles, followed by nivolumab + AVD for 6 cycles with a complete response and no evidence of disease. Asialo-GM1-associated isolated diffuse motor neuropathy in Hodgkin's lymphoma has not been previously reported in the literature. In this case report, we review the 2021 updated diagnostic criteria for the diagnosis of paraneoplastic neurological syndromes in the context of this patient presentation to highlight an instance where these guidelines do not fully capture the wide spectrum of PNS.

Scrub typhus, a zoonosis caused by Orientia tsutsugamushi (O. tsutsugamushi), remains a significant public health threat in the Asia-Pacific region. This disease is transmitted through the bite of infected trombiculid mite larvae (chiggers) and typically manifests as acute undifferentiated fever during the early stage. Despite the availability of targeted antibiotic therapies, delayed diagnosis frequently leads to severe complications and fatal outcomes. Here, we report a severe imported paediatric case in Beijing, a city in China's temperate zone, involving a 12-year-old girl with a recent travel history to Yunnan Province. The patient presented with fever, characteristic eschar, regional lymphadenopathy, and septic shock, ultimately progressing to multiorgan dysfunction syndrome. Whole-genome metagenomic next-generation sequencing (mNGS) of blood, cerebrospinal fluid (CSF), and sputum samples revealed O. tsutsugamushi with high sequence read counts, whereas blood cultures remained negative for other bacterial pathogens. Subsequent PCR amplification and Sanger sequencing confirmed the mNGS findings. Phylogenetic analysis of the TSA56 gene classified the strain within the Karp cluster. Serological analysis revealed the presence of O. tsutsugamushi-specific IgM and IgG antibodies. This severe paediatric case highlights the importance of considering travel-associated scrub typhus in the differential diagnosis of febrile illnesses in non-endemic regions. This is particularly relevant for patients with a history of insect bites in areas known to be endemic for O. tsutsugamushi.

Scrub typhus is a common cause of acute febrile illness in endemic regions; however, musculoskeletal involvement is usually limited to myalgia, and true inflammatory arthritis is rarely reported. We describe a 19-year-old previously healthy male military recruit who presented with a two-month history of progressive bilateral knee swelling and left ankle pain, accompanied by fever, weight loss, and lymphadenopathy. Clinical evaluation revealed inflammatory oligoarthritis with culture-negative synovial fluid. Given the chronicity of symptoms and systemic features, tubercular and septic arthritis were initially considered. Imaging showed preserved joint architecture, and synovial fluid analysis demonstrated inflammatory features without microbial growth. Investigations for tuberculosis, autoimmune disorders, and other tropical infections were negative. Serological testing was positive for scrub typhus immunoglobulin M using a rapid immunochromatographic assay. Following the initiation of doxycycline therapy, the patient showed rapid clinical improvement with resolution of fever and marked reduction in joint symptoms. This case highlights an uncommon presentation of scrub typhus-associated inflammatory oligoarthritis mimicking tubercular arthritis in endemic regions. Clinicians should consider scrub typhus in patients presenting with febrile oligoarthritis and culture-negative joint effusion, as early recognition and appropriate treatment can result in excellent outcomes.

Concurrent development of therapy-related acute myeloid leukemia (t-AML) and lymph node tuberculosis (LNTB) following comprehensive anti-tumor therapy for locally advanced lung squamous cell carcinoma (LSCC) is extremely rare in clinical practice. This is not a new biological concept but represents a rarely documented clinical scenario in the setting of neoadjuvant chemoimmunotherapy, surgery, and anti-PD-1 maintenance therapy. Herein, we systematically summarize the clinical features, pathogenesis and individualized therapeutic strategies of these two concurrent rare complications based on a single rare case and the latest relevant literature, to provide a reference for clinical diagnosis and treatment. A 54-year-old male patient was initially diagnosed with locally advanced LSCC. After four cycles of neoadjuvant therapy with carboplatin, albumin-bound paclitaxel and pembrolizumab, the tumor lesion regressed markedly. Thoracoscopic right upper lobectomy was then performed, followed by maintenance immunotherapy with single-agent pembrolizumab postoperatively. Four months after maintenance therapy, the patient developed abnormalities on routine blood work, low-grade fever, fatigue and superficial lymphadenopathy. t-AML was confirmed by bone marrow aspiration, immunophenotyping, gene mutation and cytogenetic examinations, accompanied by breast cancer susceptibility gene 2 (BRCA2), DNA (cytosine-5)-methyltransferase 3 alpha (DNMT3A), and isocitrate dehydrogenase 2 (IDH2) mutations, and positivity for lysine (K)-specific methyltransferase 2A partial tandem duplication (KMT2A-PTD). Meanwhile, LNTB was diagnosed by lymph node aspiration pathology combined with tuberculosis-specific assays. The patient was treated with an optimized quadruple anti-tuberculosis regimen (HZEM), and induction chemotherapy for AML with VA regimen (venetoclax plus azacitidine) plus revumenib, and supportive therapy. Subsequently, the patient achieved partial remission of leukemia, with no uncontrollable severe adverse events. In this case, LSCC was managed with neoadjuvant therapy, thoracoscopic right upper lobectomy and postoperative maintenance therapy with single agent pembrolizumab. The development of t-AML is primarily driven by cytotoxic DNA damage induced by chemotherapeutic agents, whereas the potential contribution of immune checkpoint inhibitors remains largely speculative. The potential contribution of immune checkpoint inhibitors via immune microenvironmental disturbance remains largely speculative and insufficiently documented by current clinical evidence. The impaired immune function caused by comprehensive anti-tumor therapy may further elevate the risk of LNTB. The overlapping clinical manifestations of the two concurrent diseases substantially increase diagnostic difficulty. Timely and thorough bone marrow examination, lymph node pathological biopsy and tuberculosis-specific screening are the keys to early and accurate diagnosis.

Rosai-Dorfman disease, also known as sinus histiocytosis with massive lymphadenopathy, is a rare non-Langerhans cell histiocytic disorder most commonly involving the cervical lymph nodes, which are affected in approximately 80%-90% of cases. It predominantly affects children and young adults but may occur at any age, typically presenting with painless, bilateral, and sometimes bulky cervical lymphadenopathy, occasionally associated with systemic inflammatory symptoms and laboratory abnormalities such as elevated inflammatory markers and polyclonal hypergammaglobulinemia. Histopathological examination is essential for diagnosis and demonstrates marked sinus expansion by large histiocytes with abundant pale cytoplasm and characteristic emperipolesis, set within a lymphoplasmacytic background. Immunohistochemically, these histiocytes express CD68, CD163, and S100 protein, while lacking CD1a and langerin expression, allowing distinction from other histiocytic disorders. Although historically considered a benign reactive condition, recent molecular studies have identified activating mutations in the MAPK/ERK signaling pathway, including KRAS, NRAS, and MAP2K1, in a significant subset of cases, supporting a clonal neoplastic component. The clinical course of cervical RDD is generally favorable, and management is individualized, ranging from observation to surgical excision in cases of compressive symptoms, with systemic or targeted therapies reserved for refractory or multisystem disease. We report the case of a 25-year-old patient with no significant past medical history who presented with a persistent cervical lymphadenopathy. Comprehensive clinical evaluation, laboratory investigations, and imaging studies supported the diagnosis of Rosai-Dorfman disease. Prompt recognition and appropriate surgical management play a crucial role in achieving favorable clinical outcomes.

We describe a case of systemic lupus erythematosus (SLE) that was initially misdiagnosed as syphilis because both non-treponemal and treponemal serological tests were positive. A 16-year-old female presented with lymphadenopathy and was treated for syphilis. However, further evaluation revealed highly active SLE with neuropsychiatric and renal involvement. The syphilis serology results converted to negative following immunosuppressive therapy. This case highlights an important diagnostic pitfall: in patients with suspected autoimmune diseases, both non-treponemal and treponemal tests may yield false-positive results, and syphilis serology should therefore be interpreted in conjunction with the clinical findings and disease context.

Thoracic SMARCA4-deficient undifferentiated tumor (T-SMARCA4-DUT) is a rare neoplastic entity with a high risk of being misdiagnosed. We report the case of a 64-year-old male initially suspected of having mediastinal lymphoma by contrast-enhanced chest computed tomography (CECCT), and pathologically diagnosed with metastatic poorly differentiated lung adenocarcinoma via cervical lymph node biopsy. Initial immunohistochemical (IHC) results showed TTF-1 (clone SPT24) (+), Napsin A (-), p40 (-), and next-generation sequencing (NGS) detected KRAS amplification and TP53 missense mutation. Combined chemotherapy plus immunotherapy initially shrank the tumor, but bilateral axillary lymphadenopathy subsequently developed. Pathological analysis of axillary metastases and supplementary IHC of the original cervical biopsy revealed SMARCA4/Brg1 (-), SOX2 (+) and TTF-1 (clone 8G7G3/1) (-), leading to a revised diagnosis of lymph node-metastatic T-SMARCA4-DUT. This case identifies the non-specific clinical features of T-SMARCA4-DUT and an inadequate initial IHC panel as the core causes for misdiagnosis and confirms that a definitive diagnosis requires testing for SMARCA4/Brg1, SOX2, and the highly specific TTF-1 (clone 8G7G3/1).

Male breast carcinoma (MBC) is a rare malignancy and often presents at an advanced stage due to low awareness and social stigma. Management is largely extrapolated from female breast cancer and must be individualized, particularly in elderly patients. An 87-year-old male patient presented with a painless left breast lump since three months and an ulcer over the nipple for since one month. Examination revealed a firm retroareolar mass with a healed ulcer over the lower aspect of the nipple and no palpable axillary lymphadenopathy. Imaging suggested a suspicious lesion, and core needle biopsy confirmed invasive ductal carcinoma. Staging workup with fludeoxyglucose-18 (FDG) positron emission tomography-computed tomography (PET-CT) showed no distant metastasis. The patient underwent a modified radical mastectomy with axillary lymph node dissection. Histopathology revealed Grade II invasive ductal carcinoma with nodal involvement (pT4bN1a, Stage IIIB). Immunohistochemistry demonstrated estrogen and progesterone receptor positivity, human epidermal growth factor receptor 2 (HER2) negativity, and a low proliferative index, consistent with a luminal A subtype. Following multidisciplinary tumour board discussion, adjuvant chemotherapy was omitted, considering advanced age and performance status. The patient was treated with tamoxifen and adjuvant chest wall + axillary radiotherapy. At follow-up, he remains disease-free with a good quality of life. This case highlights the importance of early suspicion in male breast lesions and emphasizes individualized management integrating tumor biology, stage, and patient factors.

Myeloid sarcoma is an uncommon extramedullary tumor composed of immature myeloid precursor cells that occurs in association with acute myeloid leukemia (AML) and other myeloid neoplasms. These tumors may arise before, concurrently with, or after the diagnosis of systemic leukemia and can involve numerous anatomical locations, including the skin, lymph nodes, gastrointestinal tract, and soft tissues. Involvement of the scrotum or testis is particularly rare and often presents diagnostic challenges due to its ability to mimic inflammatory or primary neoplastic conditions. We describe a case of a 68-year-old male who presented with persistent scrotal swelling initially treated as a scrotal abscess. Despite repeated incision and drainage procedures, the lesion persisted and was later accompanied by multiple cutaneous nodules involving the torso and lower extremities. Imaging demonstrated a heterogeneously enhancing lesion involving the scrotal wall with extension into the inguinal canal and associated lymphadenopathy. Histopathological examination with immunohistochemistry revealed tumor cells positive for myeloperoxidase and CD34 with a high Ki-67 proliferation index, confirming the diagnosis of multifocal myeloid sarcoma. The patient received induction chemotherapy with cytarabine and daunorubicin along with localized radiotherapy. However, the clinical course was complicated by febrile neutropenia and multiorgan failure, resulting in death four weeks after initiation of therapy. This case highlights the importance of considering hematologic malignancies in patients presenting with atypical or treatment-refractory scrotal swellings. Early biopsy and multidisciplinary evaluation are essential for timely diagnosis and appropriate management.