: 763 
Keratoacanthoma centrifugum marginatum is a cutaneous condition, a variant of keratoacanthomas, which is characterized by multiple tumors growing in a localized area. : 763 : 645 
Multiple keratoacanthomas (also known as "Ferguson–Smith syndrome," "Ferguson-Smith type of multiple self-healing keratoacanthomas,") is a cutaneous condition, a variant of keratoacanthomas, which is characterized by the appearance of multiple, sometimes hundreds of keratoacanthomas. : 763 : 644 
A solitary keratoacanthoma (also known as "Subungual keratoacanthoma") is a benign, but rapidly growing, locally aggressive tumor which sometimes occur in the nail apparatus. : 667, 764 : 644 
Generalized eruptive keratoacanthoma (also known as "Generalized eruptive keratoacanthoma of Grzybowski") is a cutaneous condition, a variant of keratoacanthomas, characterized by hundreds to thousands of tiny follicular keratotic papules over the entire body. : 763  : 645  Treatments are not successful for many people with generalized eruptive keratoacanthoma. Use of emollients and anti-itch medications can ease some symptoms. Improvement or complete resolutions of the condition has occurred with the application of the following medications: acitretin, isotretinoin, fluorouracil, methotrexate, cyclophosphamide. Cause
Keratoacanthomas usually occurs in older individuals. A number of causes have been suggested including ultraviolet light, chemical carcinogens, recent injury to the skin, immunosuppression and genetic predisposition. As with squamous cell cancer, sporadic cases have been found co-infected with the human papilloma virus (HPV). Although HPV has been suggested as a causal factor, it is unproven.Many new treatments for melanoma are also known to increase the rate of keratoacanthoma, such as the BRAF inhibitor medications vemurafenib and dabrafenib. Diagnosis
Keratoacanthomas presents as a fleshy, elevated and nodular lesion with an irregular crater shape and a characteristic central hyperkeratotic core.
Layers imagable with optical coherence tomography
Using optical coherence tomography (OCT) there are 18 layers that can be identified in the retina. The layers and anatomical correlation are as follows:

From innermost to outermost, the layers identifiable by OCT are as follows:

Development
Retinal development begins with the establishment of the eye fields mediated by the SHH and SIX3 proteins, with subsequent development of the optic vesicles regulated by the PAX6 and LHX2 proteins. The role of Pax6 in eye development was elegantly demonstrated by Walter Gehring and colleagues, who showed that ectopic expression of Pax6 can lead to eye formation on Drosophila antennae, wings, and legs. The optic vesicle gives rise to three structures: the neural retina, the retinal pigmented epithelium, and the optic stalk. The neural retina contains the retinal progenitor cells (RPCs) that give rise to the seven cell types of the retina. Differentiation begins with the retinal ganglion cells and concludes with production of the Muller glia. Although each cell type differentiates from the RPCs in a sequential order, there is considerable overlap in the timing of when individual cell types differentiate. The cues that determine a RPC daughter cell fate are coded by multiple transcription factor families including the bHLH and homeodomain factors.In addition to guiding cell fate determination, cues exist in the retina to determine the dorsal-ventral (D-V) and nasal-temporal (N-T) axes. The D-V axis is established by a ventral to dorsal gradient of VAX2, whereas the N-T axis is coordinated by expression of the forkhead transcription factors FOXD1 and FOXG1.