Photoreceptor cell differentiation in retinoblastoma demonstrated by a new immunohistochemical marker mucin-like glycoprotein associated with photoreceptor cells (MLGAPC).
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.
Tsuji
M
M
Department of Ophthalmology, Faculty of Medicine, Kagoshima University, Kagoshima, Japan.
Goto
M
M
Uehara
F
F
Kaneko
A
A
Sawai
J
J
Yonezawa
S
S
Ohba
N
N
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*
D014408:Biomarkers, Tumor; D006023:Glycoproteins; D009077:Mucins