[Epithelial tumor-like changes, precancerous conditions and skin neoplasms (standardization study)].

A retrospective study of bioptic material was used to design the following outline of a histological classification of epithelial skin tumours tentatively compared with handbooks published by the WHO (1) and AFIP (2): I. Tumour-like changes: 1. senile verruca (mixed, acanthotic, melanoacanthotic, hyperkeratonic, reticular, inverted). 2. Virus verrucosities (v. vulgaris, v. plana, c. accuminatum, molluscom contagiosum). 3. Hamartogenic verrucosities (naevus verrucosus, n. comedonicus, fibroepithelial papilloma. 4. Genetically undefined verrucosities (acanthosis nigricans, light cell acanthoma, verrucous dyskeratosis). 5. Cysts (atheroma, epidermoid cyst, dermoid cyst, others). 6. Unclassified. II. Precanceroses: 1. Pseudoepitheliomatous hyperplasis, 2. keratosis senilis, 3. Radiation dermatosis, 4. Unclassified. III. Epithelial tumours A. From surface epithelium 1. Spinocellular carcinoma (basic type, anaplastic, adenoid, sarcomatoid, clear cell carcinoma, intraepidermal). 2. Basocellular carcinoma: a) varieties derived from surface epithelium (intraepithelial, superficial, solid, cystic, invasive), b) varieties with adenoid features (cylindromatous, fibroepithelia), c) varieties with trichoepithelial features (keratinizing, pigment-type, clear cell type), d) naevus varieties (basocellular naevi). 3. Spinobasocellular carcinoma. 4. Unclassifiable. B. Sweat gland tumours: 1. syringocystadenoma papilliferum, 2. hidradenoma papillare, 3. nodular hidradenoma (eccrine spiradenoma, eccrine acrospiroma, myxochondroepithelioma, myoepithelioma, mucinous epithelioma), 4. syringoma, 5. eccrine cylindroma, 6. hidrocystoma, 7. eccrine poroma, 8. carcinomas (so called extramammary Paget carcinoma), 9. unclassifiable. C. Sebaceous gland tumours: 1. adenoma sebaceum, 2. carcinoma sebaceum, 3. quasi tumours (naevus sebaceus, Pringle's hamartoma, steatocystoma multiplex, hyperplasia), 4. unclassifiable. D. Trichoepithelial tumours: 1. trichofolliculoma, 2. follicular poroma, 3. keratoacanthoma, 4. tricholemoma, 5. pilomatrixoma, 6. trichogenic adnexal tumour, 7. trichoepithelioma, 8l unclassifiable.