title: Photoreceptor cell differentiation in retinoblastoma demonstrated by a new immunohistochemical marker mucin-like glycoprotein associated with photoreceptor cells (MLGAPC).
abstract: OBJECTIVE
  For further understanding of specific differentiation in retinoblastoma, we studied the expression of newly detected mucin-like glycoprotein associated with photoreceptor cells (MLGAPC), which is specific for photoreceptor cells of retina and analogous to interphotoreceptor matrix proteoglycan-1 (IMPG1).
  
  
  RESULTS
  Surgically enucleated retinoblastomas (n=21; undifferentiated type, n=15, differentiated type, n=6) were immunohistochemically studied with a polyclonal antibody against MLGAPC, and 17/21 cases (81%) showed positive staining of tumour cells. We classified various staining patterns and structures into four groups: type 1 showing a granular intracellular scattered staining pattern with round small cells; type 2 showing a reticular staining pattern between spindle-shaped tumour cells; type 3 showing radiating staining from the centre of Homer-Wright rosettes; type 4 showing ring-shaped, radiating and granular staining associated with Flexner-Wintersteiner rosettes. Eleven of 15 undifferentiated retinoblastomas (73%) showed type 1 or 2, and all the six differentiated cases showed type 3 or 4. Image analysis of immunostaining revealed an increase in MLGAPC-positive area from 0.48% in undifferentiated cases to 1.60% in differentiated cases, and a negative correlation was shown between mitotic frequency and MLGAPC-positive area.
  
  
  CONCLUSIONS
  This study proved MLGAPC as a valuable marker of retinoblastoma, and that photoreceptor differentiation takes place even in 'undifferentiated' retinoblastoma.
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Kagoshima University, Kagoshima, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tsuji
authors.forename: M
authors.initials: M
authors.lastname: Goto
authors.forename: F
authors.initials: F
authors.lastname: Uehara
authors.forename: A
authors.initials: A
authors.lastname: Kaneko
authors.forename: J
authors.initials: J
authors.lastname: Sawai
authors.forename: S
authors.initials: S
authors.lastname: Yonezawa
authors.forename: N
authors.initials: N
authors.lastname: Ohba
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000378:metabolism / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007124:Immunoenzyme Techniques; D007223:Infant; D008297:Male; D008938:Mitosis; D009077:Mucins / Q000378:metabolism; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism / Q000473:pathology*; D019572:Retinal Neoplasms / Q000378:metabolism / Q000473:pathology*; D012175:Retinoblastoma / Q000378:metabolism / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor; D006023:Glycoproteins; D009077:Mucins