squamous cell carcinoma, basosquamous carcinoma, collision tumors with any epithelioma as a component (e.g., with seborrheic keratosis), keratoacanthoma, fibroepithelioma, and lymphoepithelioma-like carcinoma of the skin, “melanocytic nevi” 𝑛 = 965 (17.2%), “benign tumors and cysts” 𝑛 = 700 (12.5%), “dermatitis” 𝑛 = 484 (8.6%), “papulosquamous dermatoses” 𝑛 = 425 (7.6%), “premalignant skin lesions” 𝑛 = 253 (4.5%), “connective tissue diseases” 𝑛 = 244 (4.4%), “conditions of the skin appendages and acneiform eruptions” 𝑛 = 205 Dermatology Research and Practice 3 Table 1: Frequencies and percentages of a classification describing the relationship between clinical and histological diagnoses. Case Frequency Percentage Case 1: one specific histological diagnosis inconsistent with the unspecified clinical diagnoses 207 3.1 Case 2: one specific histological diagnosis consistent with one specific clinical diagnosis 2642 39.3 Case 3: one specific histological diagnosis consistent with at least one clinical diagnosis regarding the disease category 1668 24.8 Case 4: one specific histological diagnosis inconsistent with the specific clinical diagnoses 1080 16.1 Case 5: no specific histological diagnosis without usable features inconsistent with the specific clinical diagnoses 162 2.4 Case 6: no specific histological diagnosis inconsistent with the unspecified clinical diagnoses 25 0.4 Case 7: no specific histological diagnosis but with usable features, inconsistent with the specific clinical diagnoses 567 8.4 Case 8: two or more specific histological diagnoses constituting subset of the proposed clinical diagnoses 50 0.7 Case 9: two or more specific histological diagnoses different from the proposed clinical diagnoses 108 1.6 Case 10: two or more specific histological diagnoses exhibiting partial overlap with the proposed clinical diagnoses 211 3.1 Total 6720 100.0 (3.7%), “cutaneous vasculitides” 𝑛 = 135 (2.4%), “drug eruptions and urticaria” 𝑛 = 106 (1.9%), “immunobullous diseases” 𝑛 = 101 (1.8%), “noninfectious granulomas” and granulomatous diseases 𝑛 = 99 (1.7%), “malignant melanomas” 𝑛 = 84 (1.5%), “other malignancies” besides melanomas and epitheliomas 𝑛 = 70 (1.3%), “cutaneous infections” 𝑛 = 61 (1.1%), and miscellaneous dermatoses 𝑛 = 441 (7.9%). Performing the chi-square test, the differences in the frequencies were found statistically significant (𝜒2 = 5150.109, 𝑃 < 0.001). Also, applying the test for contingency tables, the site of biopsy and histological diagnosis were found dependent (𝜒2 = 2917.638, 𝑃 < 0.001) with the most important associations being between epitheliomas followed by conditions of the skin appendages in the head and neck region, cutaneous vasculitides on the lower extremities, melanocytic nevi on the posterior tegument, and dermatitis on the anterolateral tegument. Among the 259 different expressions used by the dermatopathologists, the most common were “junctional, compound, and intradermal nevi” 𝑛 = 903 (16.1%), “basal cell carcinoma” 𝑛 = 858 (15.3%), and “squamous cell carcinoma” 𝑛 = 304 (5.4%). 3.5. Relationship between Clinical and Histological Diagnosis. As mentioned before, 5597 specific histological diagnoses were proposed regarding the underlying pathology of 6720 skin biopsies. In the remaining cases, either a differential diagnosis was offered or no particular suggestion was made. In order to assess the relationship between clinical and histological diagnoses, a classification of ten cases that occurred was employed and for that purpose a separate evaluation was made. The observed frequencies and percentages along with the description of the ten cases are presented in Table 1. A specific histological diagnosis was provided in 𝑛 = 5597 instances (83.3%), no specific histological diagnosis in 𝑛 = 754 (11.2%), whereas two or more were proposed in 𝑛 = 369 (5.5%) of the cases. Useful data orientating the dermatologist in establishing a final clinical diagnosis (cases 1–4 and 7–10 in Table 1) was provided in 𝑛 = 6533 (97.2%) of all biopsies. Histological and clinical diagnoses were found substantially consistent (cases 2, 3, 8, and 10 in Table 1) in 𝑛 = 4571 (68%) of instances. The dermatologists did not provide any