Abstract Congenital and self-healing Hashimoto-Pritzker reticulohistiocytosis is the benign variant of the Langerhans cell histiocytosis (LCH) group. It is characterized by multiple skin lesions (congenital or appearing during the first days after birth), without systemic manifestations and spontaneous resolution in days to months. The authors report the case of a boy with a single congenital leg skin lesion, a rare disease variant. Through histopathology, a dense skin infiltration of S100 protein-, CD1a-, CD207-immunomarked cells was found. KI67 index was high (62%). A complete spontaneous resolution occurred 07 days after the biopsy (25 days after birth). Monolesional disease, distal limb lesion, absence of lesions in the mucous membrane or seborrheic area, and less than 25 percent of LCs with Birbeck granules were said to be possible clues for a favorable prognosis in LCs histiocytosis. But, as a precautionary measure, the child will be followed up until at least 2 years of age.

O diagnóstico diferencial entre a variante pequenas células do carcinoma epidermoide e do carcinoma de pequenas células nem sempre é fácil. Apesar de os descritores alertarem que o primeiro deva manter suas características morfológicas e, muitas vezes, diferenciação escamosa focal, a escassez de material aliada a artefatos de fixação frequentes nessas biópsias podem dificultar a vida do patologista. Entretanto, a definição entre um e outro pode alterar significativamente a escolha da modalidade terapêutica do paciente e, em alguns casos, influenciar seu prognóstico. Procuramos nesta publicação alertar para o problema e facilitar essa diferenciação, sugerindo um painel imuno-histoquímico.

The differential diagnosis between small cell variant of squamous carcinoma and small cell carcinoma is not always simple. Despite the fact that studies show the former keeps its morphologic characteristics and focal squamous differentiation, the scarcity of the material as well as frequent fixation artifacts in these biopsies may hinder analysis. However, this differentiation between them may change significantly the choice of therapeutic approach and, in some cases, influence prognosis. In this paper, we draw attention to this problem and suggest a immunohistochemical panel to facilitate this differential diagnosis.