title: Differentiation between Melanin-Laden Macrophages and Melanoma Cells in Vitreous Aspirates.
abstract: OBJECTIVE
  The differential diagnosis between retinal detachment and melanoma metastatic to the vitreous can be challenging, both clinically and cytologically. We demonstrate the diagnostic features and pitfalls of the cytological assessment.
  
  
  METHODS
  A case of a metastatic melanoma to the vitreous is compared to a case of retinal detachment initially suspected as melanoma metastasis. Case 1 was a 54-year-old patient with a vague history of pigmented lesions 20 years previously and a current presentation of a visual defect. Case 2 was a 68-year-old patient with a history of melanoma and a presentation of floaters and flashing lights.
  
  
  RESULTS
  The vitreous fluid of case 1 contained atypical, pigment-laden cells positive for HMB-45 and assessed as melanoma. On enucleation, a melanoma metastatic to the vitreous was diagnosed. The vitreous fluid of case 2 revealed atypical cells containing pigment granules. The cells were negative for melanocytic markers, while the granules stained positive for melanin. Macrophage marker CD163 was positive in all cells. The interpretation was one of macrophages reactive to the retinal detachment.
  
  
  CONCLUSIONS
  Melanin-laden macrophages can mimic melanoma cells. This needs to be considered in the differential diagnosis. Additional stains can help the distinction.
authors.affiliation: Basildon and Thurrock Hospital, University College London Medical School, Essex, UK.
authors.forename: Ernest
authors.initials: E
authors.lastname: Iakovlev
authors.forename: Zeina
authors.initials: Z
authors.lastname: Ghorab
authors.forename: Hatem
authors.initials: H
authors.lastname: Krema
authors.forename: Vladimir
authors.initials: V
authors.lastname: Iakovlev
authors.forename: Peter
authors.initials: P
authors.lastname: Kertes
authors.forename: Yeni
authors.initials: Y
authors.lastname: Yucel
mesh_terms: D000368:Aged; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008264:Macrophages / Q000378:metabolism*; D008543:Melanins / Q000378:metabolism*; D008545:Melanoma / Q000175:diagnosis* / Q000556:secondary; D008875:Middle Aged; D011956:Receptors, Cell Surface / Q000378:metabolism; D014822:Vitreous Body / Q000473:pathology*; D000098902:CD163 Antigen
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000098902:CD163 Antigen; D008543:Melanins; D011956:Receptors, Cell Surface