Verruga peruana mimicking malignant neoplasms.

We have shown that in some cases fully developed florid verruga peruana nodules, as well as late-resolving, deeply situated lesions, can histologically suggest a variety of tumors to experienced pathologists. The compact proliferation of endothelial cells characteristic of florid verruga lesions can give rise to two pseudoneoplastic histologic patterns. One consists of sheets or islands of cells arranged in an epithelioid or pseudoepithelioid pattern (cases 1 and 2) in which the following histologic diagnoses were considered: squamous carcinoma, sweat gland carcinoma, epithelioid hemangioendothelioma, epithelioid sarcoma, melanoma and metastatic carcinoma. The other pattern of the florid lesion is characterized by a predominantly spindle cell arrangement (case 3) and in it the following diagnoses were made: Kaposi's sarcoma, fibrosarcoma, melanoma and leiomyosarcoma. The dense lymphoplasmacytic and histiocytic infiltrates of the late-resolving, deeply situated nodules (case 4) suggested the following histologic conditions: malignant lymphoma, nodular Hodgkin's disease, reticuloendotheliosis, and reticulosarcomatosis. Some histologic features thought to be of value to help in the differential diagnoses are discussed. It is emphasized that only the finding of Rocha-Lima's inclusions on light-microscopic studies and/or the demonstration of bartonella organisms in the lesions by electron-microscopic studies can objectively establish a diagnosis in a given lesion. However, knowledge of the epidemiologic data and particularly the presence of other lesions in the patient make it relatively easy to rule out neoplasia.