Background: Histopathological examination of skin tissue plays an important role in the diagnosis of dermatological diseases; however, data on surgically excised skin specimens remain limited in Mongolia. Aim: To classify benign and malignant tumors based on histopathological findings of surgically excised skin tissue specimens, determine surgical margin status, and evaluate the age and sex distribution of these conditions. Materials and Methods: This retrospective observational study was conducted using data on surgically excised tissue specimens collected in the outpatient department of the National Dermatology Center between January 2023 and March 2026. A total of 361 patients were identified. Four cases with indeterminate histopathological diagnoses were excluded, leaving 357 patients for final analysis. Data on age, sex, diagnosis, and surgical margin status were collected and analyzed on Microsoft Excel programm. Histopathological diagnoses were classified as benign or malignant tumors. Associations between categorical variables were assessed using the chi-square test, with statistical significance set at p < 0.05. Results: Among 357 patients, 135 (37.8%) were male and 222 (62.2%) were female, with a mean age of 41.8 years. The 20–39-year age group accounted for the largest proportion of cases (39.5%). Histopathological examination showed that 326 cases (91.32%) were benign and 31 cases (8.68%) were malignant. Among benign tumors, melanocytic nevus was the most common diagnosis, while basal cell carcinoma was the most common malignant tumor. The frequency of malignant tumors increased significantly with age (p < 0.001). Patients aged ≥60 years had significantly higher odds of malignancy compared with younger patients (OR = 8.19, 95% CI: 3.79–17.69). Malignant lesions were significantly more likely to have positive (involved) surgical margins than benign lesions. Conclusion Most surgically excised skin tissue specimens were benign; however, the likelihood of malignancy increased significantly with age. Surgical margin assessment is clinically important for improving prognosis, reducing the risk of recurrence, and guiding treatment management.