Histiocytic Nodules

• Nodular aggregates of histiocytes resembling Langerhans'/interdigitating cells can occur in the  endometrium. The examples described by Kim et al. were an incidental microscopic finding in curettage specimens in women of reproductive age. The nodules were solitary and 0.3-1.5 cm in maximum.
• The histocytes are round to polygonal with distinct cytoplasmic borders and moderate amounts of pale amphophilic or eosinophilic granular cytoplasm. Small cytoplasmic vacuoles, but not cytoplasmic lipid or pigment, may be present. The avoid to reniform nuclei have occasional grooves, fine chromatin, and inconspicuous nucleoli. Mitoses were frequent in one case.
• The cells are immunoreactive for CD68 and lysozym but negative for S100 and cytokeratin.
• Uterine involment by Langerhans' cell histocytosis can be excluded by the absence of eosinophils as well as negative staining for S100. The distinctive apperance of the histiocytes, their nodular arrangement, and the absence of lipid and/or pigment xanthogranulomatous endometritis.