Background: Chronic eosinophilic leukemia (CEL) is a rare, slowly progressive hematologic malignancy characterized by clonal proliferation of eosinophils in the bone marrow due to underlying genetic mutations. Persistent eosinophilia (>1.5 x 10⁹/L) for 1–6 months is a key diagnostic criterion. The presence of the FIP1L1::PDGFRA fusion gene and increased blast or abnormal cells in the bone marrow further supports the diagnosis. Case presentation: A 63-year-old male presented with symptoms of dry skin, pruritus, skin rash, enlargement of cervical, axillary, and inguinal lymph nodes, headache, and edema. According to the medical history, the disease began 4 years earlier with pruritus in the lower legs and progressed over the past 2 years with worsening skin rash. Complete blood count revealed eosinophilia of 48.6%. Based on leukogram, myelogram, skin histopathology, and cytogenetic analysis performed in China, a diagnosis of chronic eosinophilic leukemia was established. The patient responded well to treatment with imatinib and hydroxycarbamide. Conclusion Clinical manifestations of chronic eosinophilic leukemia are often nonspecific and may be misdiagnosed as dermatological conditions. Therefore, cytogenetic analysis (including FISH), leukogram, myelogram, and skin histopathological examination play a crucial role in accurate diagnosis.

Background: Rosai–Dorfman disease (RDD) is a rare, benign disorder of non-Langerhans cell histiocytic origin with an unknown etiology, which can affect the skin and other organ systems. The incidence in the United States is approximately 1:200,000. In Mongolia, four cases have been registered over the past five years under the ICD-10 code D76.0. Case presentation: A 59-year-old female patient initially presented to the Dermatology Department of the National Center for Dermatology with clustered, elevated lesions on the medial aspect of the right thigh, including papules, plaques, and nodules of round to oval shape. Additionally, multiple erythematous macules and papules were observed on both lower legs. For diagnostic purposes, a histopathological examination was performed, revealing histiocytes with abundant cytoplasm and lymphocytes within the cytoplasm (emperipolesis). The diagnosis was confirmed based on dermoscopic and immunohistochemical findings. Management: The patient was referred to the Mongolian-Japanese Hospital of MNUMS, where the remaining nodular lesions were surgically excised in the surgical department. Further follow-up was referred to a hematologist. Computed tomography (CT) imaging was recommended. Cutaneous-limited RDD may resolve spontaneously in some cases; however, when multiple organ systems are involved or when associated forms are present, referral to hematology and oncology specialists for systemic therapy is required. Conclusion It is important to differentiate this disease from other dermatological conditions presented with macules, papules, and nodules through clinical evaluation, histopathology, immunohistochemistry, and dermoscopic examination.

Background: Senear-Usher Syndrome, also known as pemphigus erythematosus, is a rare autoimmune blistering skin disease characterized by overlapping clinical, histopathological, and immunological features of both lupus erythematosus and pemphigus foliaceus. Case Presentation: We report the case of a 46-year-old male diagnosed with Senear-Usher Syndrome, who presented to the outpatient clinic of the National Dermatology Center of Mongolia and received inpatient treatment. Diagnosis: The patient exhibited diffuse, thick, pale gray scales and yellowish crusts on the scalp. Multiple brown hyperpigmented macules of various shapes and sizes, vivid erythema, and a few erosions were observed on the nose, cheeks, trunk, and upper and lower extremities. A few pea-sized vesicles containing clear fluid were scattered on the back. Nikolsky's sign was weakly positive, and Besnier-Meshchersky's sign was positive. Histopathology: Histopathological analysis of skin biopsies revealed hyperkeratosis, parakeratosis, and acanthosis in the epidermis. Subcorneal cleft formation with neutrophils within the cleft was noted, along with perivascular infiltration of neutrophils and lymphohistiocytes in the superficial dermis. Treatment: The patient received treatment with hydroxychloroquine, systemic and topical corticosteroids, and symptomatic therapy. Outcome: Following treatment, the patient's general condition improved significantly. The erosions re-epithelialized, and the vesicles resolved, leaving behind brown hyperpigmented macules. The patient is currently under regular follow-up by a dermatologist and a family physician. Conclusion Senear-Usher Syndrome is a rare disease with a high potential for misdiagnosis. Therefore, an accurate diagnosis relies on a comprehensive evaluation of clinical features, histopathological examination, and direct and indirect immunofluorescence studies.

Background: Cutaneous squamous cell carcinoma (cSCC) accounts for approximately 20% of all malignant skin tumors and is the second most common skin cancer worldwide. Although the prognosis is generally favorable when diagnosed at an early stage, large tumors with invasion into surrounding tissues and metastasis to regional lymph nodes tend to exhibit more aggressive behavior. In particular, reconstruction of large tissue defects following wide excision of skin tumors remains a significant clinical challenge. Case presentation: We present a rare case of cSCC in a 69-year-old male patient, located on the left hip. The lesion measured 13x9 cm, with well-demarcated borders from the surrounding normal skin, prominently elevated above the skin surface, and characterized by a bluish-brown color. The central superior portion of the lesion was depressed and ulcerated with infiltrative features. Histopathological examination confirmed a well-differentiated, keratinizing invasive cutaneous squamous cell carcinoma. Computed tomography revealed a soft tissue density mass at the skin surface of the left lower abdomen, along with enlargement of the left inguinal lymph nodes. Treatment: The patient underwent wide local excision of the tumor along with regional lymph node dissection (lymphadenectomy). The resulting large tissue defect was reconstructed using an anterolateral thigh (ALT) free flap. During surgery, indocyanine green (ICG) angiography was performed to assess flap perfusion, and handheld Doppler was used to evaluate vascular flow. Results: The postoperative course was uneventful. The flap survived successfully with adequate perfusion. Histopathological examination confirmed negative surgical margins, and no metastasis was identified in the lymph nodes. The patient remains in stable condition without any complaints or symptoms and is under regular follow-up by an oncologist. Conclusion This case demonstrates that combining wide excision with free flap reconstruction is an effective approach for managing large cSCC. In addition, the use of indocyanine green (ICG) angiography for intraoperative assessment of vascular perfusion enhances flap viability and contributes to improved surgical outcomes.