Case for diagnosis
A 72-year-old man presented erythematous and scaled plaque on the right neck for three\nmonths (). The lesion grew progressively\nin size with no pain and pruritus. He had no symptom of fever, malaise or weight loss.\nPhysical examination revealed no sign of lymph node enlargement in the bilateral parts\nof neck, axillary fossa and groin. Laboratory investigations indicated that the routine\nhaematological and biochemical studies were normal. The skin biopsy specimen revealed\ndiffuse inflammatory infiltrate consisting of lymphocytes, histiocytes, sparse\npopulation of neutrophils and plasma cells in the dermis (). Some histiocytes contained lymphocytes, neutrophils, plasma cells\nand RBCs within their pale and foamy cytoplasm (). Immunohistochemical staining revealed that histiocytes were positive for\nS-100 protein and CD68, but negative for CD1a ( e ).