Clear cell change in a lower lip mucocele
A 74-year-old man was referred presenting an asymptomatic nodular lesion on his lower lip with 1 month duration. The clinical diagnosis was oral mucocele. The medical history was noncontributory and the extra-oral examination did not show alterations. Microscopic sections, at lower magnification, showed a dense population of clear cells surrounding an inner cavity [Figure and ], which contained sparse to absent mucoid material. At the periphery, the clear cells displayed irregular infiltration into adjacent minor salivary gland parenchyma as broad sheets and cords, being supported by a dense fibrous stroma. In high-power, the cells showed clear cytoplasmic vacuolation with shrunken, pyknotic peripheral nuclei [] and a SRC appearance, intermingled with a delicate network of small vessels []. Periodic acid-Schiff and mucicarmine stains revealed focal areas with homogeneous mild positivity, consistent with intracellular mucin []. Despite these diagnostic approaches, definitive diagnosis still could not be achieved, because both epithelial cells and macrophages may contain cytoplasmic mucin. Therefore, immunohistochemical analysis was indicated, which showed strong positivity for CD68 (KP1) and CD163 [], whereas AE1/AE3 pan-cytokeratin, S100, HMB-45 and CD1a were negative, supporting a macrophage lineage cell. The post-surgical evaluation did not reveal any abnormality and after 3 years of follow-up the patient is well without complications.