<prompt> Upper GI endoscopy and biopsy from lower esophagus in a 48 year old lady with chronic heart bum shows presence of columnar epithelium with goblet cells. The feature is most likely consistent with :Dysplasia.Hyperplasia.Carcinoma in-situ.Metaplasia.  <response>: Ans. is d i.e. Metaplasia Normally esophagus has squamous epithelium. Presence of another type of epithelium i.e. columnar in esophagus indicates metaplasia.Metaplasiais an abnormality of cellular differentiation in which one type of mature cell is replaced by a different type of mature cell, and the latter is not normal for the tissue involvedOther questions on metaplasia; -Metaplasia is reversibleMetaplasia most commonly involves epitheliumMetaplastic tissue is structurally normal and itself carries no increased risk of development of cancer.Dysplasiais abnormality of both differentiation and maturation. It is characterized by: -Nuclear abnormalitiesincreased nuclear: cytoplasmic ratiohyperchromatismabnormal chromatin distribution chromatin clumpingCellular pleomorphism variation in size and shape of cellsMitotic figures are seen in many layers of the epithelium in contrast to the normal state, in which mitosis in limited to the basal layer.Dysplasia is reversibleCarcinoma in situ -When the dysplastic changes involve the entire thickness of the epithelium, it is referred to as carcinoma in situHyperplasiais an increase in the size of a tissue as a result of increased number of component cells.eg. breast hyperplasia in pregnancy and lactation. Prostate hyperplasia in older men. Thyroid hyperplasia in Graves disease.The following flow chart may be very useful in understanding various abnormalities of cell growth and differentiation.Abnormal differentiationReplacement of mature cells of one type with cells of another typeRegular organization of tissue maintainedReversibleAbnormal differentiation and maturationPartial loss of control and organizationSlight increase in cell numberCytologic abnormalitiesPartially reversibleAbnormal differentiation and maturationMarked increase in cell numberComplete loss of controlVariable loss of organizationCytologic abnormalitiesIrreversible 