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Introduction Keratoacanthoma is a fast-growing crateriform skin tumor. Approximately 25% of such tumors undergo malignant transformation and develop areas of squamous cell carcinoma (SCC). The presence of laminin-322 has been associated with progression to invasive forms of SCC. The aim of this study was to determine whether or not immunohistochemical staining for laminin-322 would be of value in distinguishing between keratoacanthomas, keratoacanthomas with areas of squamous cell carcinoma, and SCCs. Material and methods Seventy-four lesions were selected from the pathology archives of our hospital and divided into 4 groups: 20 keratoacanthomas without SCC, 20 keratoacanthomas with areas of squamous cell carcinoma, 20 invasive SCCs (8 with crateriform morphology) unrelated to keratoacanthoma, and 14 problem lesions (keratoacanthomas with areas suggestive of SCC). All 74 lesions were stained for laminin-322. Results Laminin-322 staining was strongly positive both in areas of SCC in keratoacanthomas with malignant transformation and in invasive SCCs (mostly at the invasive front of the SCC). However, in benign keratoacanthomas, it was only weakly positive and furthermore it was confined to isolated cells or small groups of cells. The 14 problem lesions were reexamined after laminin-322 staining and 8 were diagnosed as keratoacanthomas with incipient SCC and 6 as keratoacanthomas without SCC. Conclusions Laminin-322 staining is different in keratoacanthomas and SCCs and would thus be a useful test for differentiating keratoacanthomas from both invasive SCCs and keratoacanthomas with areas of squamous cell carcinoma. It would also be of value in diagnosing keratoacanthomas with areas suggestive of SCC or with incipient SCC.

Resumen Introduccion El queratoacantoma (QA) es un tumor cutaneo crateriforme, de crecimiento rapido; aproximadamente el 25% de los QA presentan transformacion maligna (QAm), observandose areas de carcinoma epidermoide (CE). La laminina-332 se ha relacionado con progresion a fases invasoras en diversos CE. El objetivo de este estudio es evaluar si la tincion con laminina-332 es util para distinguir QA, QAm y CE. Material y metodos Seleccionamos 74 casos del archivo de Anatomia Patologica. Se analizaron 4 grupos: 20 QA sin CE, 20 QAm con areas evidentes de CE, 20 CE invasores sin relacion con QA (8 con morfologia crateriforme) y 14 casos «problema» (QA con «dudosas» areas de CE). Posteriormente se realizo tincion inmunohistoquimica para laminina-332 a todas estas lesiones. Resultados En las areas de CE asociado a QAm y en los CE invasores, la tincion con laminina fue positiva de forma intensa, habitualmente en el frente invasor del CE, a diferencia de los QA, en que la tincion fue positiva solo de forma debil y focal, en celulas aisladas o en pequenos «grupos» celulares. Los casos «problema» se reexaminaron tras valorar la tincion con laminina-332 (8 se diagnosticaron de QA con CE incipiente, 6 de QA sin CE). Conclusiones La tincion con laminina-332 es diferente en los QA respecto a los CE, por lo que ayudaria a diferenciar los QA de los CE invasores y de las areas de CE en QAm, asi como en el diagnostico de QA con «dudosas» areas de CE y QA con CE incipientes.