A 27-year-old presented with papular skin rash in the inguinal region and palpable right inguinal lymphadenopathy. Excisional biopsy of right inguinal lymph node was performed and the histopathology is shown in Figure 1.
The correct answer is ...
Dermatopathic lymphadenopathy is characterized by paracortical expansion by small lymphocytes, histiocytes, and Langerhans cells.(1) The sinuses are patent. Pigment laden macrophages (arrow, Figure 1) can be seen. CD1a marks the paracortical expansion by the Langerhans cell in a similar distribution to CD3-positive T-lymphocytes in the paracortex.
Rosai-Dorfman disease (RDD) is a non-Langerhans cell histiocytosis also known as sinus histiocytosis with massive lymphadenopathy. Morphologically, RDD is characterized by emperipolesis (engulfment of inflammatory cells by large histiocytes) with expression of CD68, CD163, S100, and negative for CD1a and langerin.
Langerhans cell histiocytosis (LCH) is characterized by infiltration of Langerhans cells restricted to the lymph node sinuses.(1) The pattern of distribution of Langerhans cells is the key morphologic feature to distinguish LCH from dermatopathic lymphadenopathy.
Erdheim-Chester disease (ECD) is a non-Langerhans cell histiocytosis and a clonal systemic process with multiorgan involvement and variable clinical outcomes. Typical clinical presentation of ECD includes central diabetes insipidus, perinephric fibrosis, and sclerotic bone lesions. The lesional histiocytes strongly express CD68, CD163, Factor XIIIa, and are negative for CD1a and langerin. BRAF V600E is positive in a subset of cases.
Aishwarya Ravindran, M.B.B.S.
Karen Rech, M.D.
Associate Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science