Balmer and Munier Figure 2 (a) Small endophytic unifocal retinoblastoma. (b) Unifocal juxtapapillary lesion involving the macular, with xanthophile pigment visible superiorly. (c) Multifocal retinoblastoma with foci visible beneath the detached retina and superﬁcial vascular anomalies. (d) Multifocal retinoblastoma with calciﬁcations and massive vitreous seeding. phytic growth, while that developing from the external layers, invading the subretinal space and causing a retinal detachment an exophytic growth. A mixed growth involves the association of these two types. More rarely (2%), the tumor may develop in an insidious manner within the retinal layers and subretinal space, with no elevated mass and no calciﬁcations, growing slowly along the retinal axis towards the anterior segment where late manifestations of the disease occur in the form of pseudo- inﬂammatory complications. This is the diffuse inﬁltrating, or plaque-like form of retinoblastoma (Morgan 1971). Endophytic retinoblastoma (Figures 2a and 2b) presents as one or more isolated or coalesced tumors of variable size, round or oval-shaped, yellowish-white (calciﬁcations) or pink- ish (vascularization) in color with its own, often turgescent and tortuous, vascular network. Endophytic retinoblastoma shows a marked tendency to invasion of the vitreous by seeding. Exophytic retinoblastoma (Figure 2c), developing outside the retina towards the choroid, causes a retinal detachment that 434 masks to a greater or lesser degree the details of the underlying mass or masses. Seeding may occur in the subretinal ﬂuid. Both endo- and exophytic forms are likely to develop calciﬁcations, in the form of chalky white patches within the tumoral mass. Vitreous and subretinal seeding, along with calciﬁcations, are the characteristics virtually pathognomonic of retinoblastoma (Figure 2d). The diffuse inﬁltrating form, however, presenting as a greyish retinal coating with no elevated mass and no calci- ﬁcations, may ﬁnally manifest as a pseudo-hypopion (Morgan 1971; Girard et al 1989). Finally, in probably 2%–5% of cases (Balmer and Munier 2002a), retinoblastoma may present in an inactive form indicative of spontaneous remission, called reti- noma or, to use the histopathological term, retinocytoma. This is characterized by homogenous, more or less translucent greyish masses, calciﬁcations, with pigment migration and proliferation bordering the tumor (Gallie et al 1982). In all respects, retinoma resembles a retinoblastoma sterilized by radiotherapy, without ever having undergone any treatment whatsoever. Clinical Ophthalmology 2007:1(4)