abnormal epidermis stratum granulosum morphology epidermis stratum granulosum hyperplasia granular layer hyperplasia overdevelopment or increased size, usually due an increased number of cells, of the layer of flattened cells containing basophilic granules of keratohyalin and lying just above the stratum spinosum (spiny layer) of the epidermis stratum granulosum hyperplasia MP:0009601 epidermal granular layer hyperplasia MPheno.ontology