Pleomorphism is a term used in histology and cytopathology to describe variability in the size, shape and staining of cells and/or their nuclei. Several key determinants of cell and nuclear size, like ploidy and the regulation of cellular metabolism, are commonly disrupted in tumors. Therefore,  cellular and nuclear pleomorphism is one of the earliest hallmarks of cancer progression and a feature characteristic of malignant neoplasms and dysplasia. Certain benign cell types may also exhibit pleomorphism, e.g. neuroendocrine cells, Arias-Stella reaction. A rare type of rhabdomyosarcoma that is found in adults is known as pleomorphic rhabdomyosarcoma.Despite the prevalence of pleomorphism in human pathology, its role in disease progression is unclear. In epithelial tissue, pleomorphism in cellular size can induce packing defects and disperse aberrant cells. But the consequence of atypical cell and nuclear morphology in other tissues is unknown. See also
Anaplasia
Cell growth
Cytopathology
Giant cell carcinoma of the lung
Nuclear atypia


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Macrocytosis is the enlargement of red blood cells with near-constant hemoglobin concentration, and is defined by a mean corpuscular volume (MCV) of greater than 100 femtolitres (the precise criterion varies between laboratories). The enlarged erythrocytes are called macrocytes or megalocytes (both words have roots meaning "big cell"). As a symptom its cause may be relatively benign and need no treatment or it may indicate a serious underlying illness. Causes
In humans, most commonly (especially when the increase in size is mild, and just above normal range) the cause is bone marrow dysplasia secondary to alcohol use disorder. Poor absorption of vitamin B12 in the digestive tract can also cause macrocytosis. Gastrointestinal diseases that may cause macrocytosis include celiac disease (severe sensitivity to gluten from wheat and other grains that causes intestinal damage) and Crohns disease (inflammatory bowel disease that can affect any part of the gastrointestinal tract). Other causes may include:

megaloblastosis (vitamin B12 or folate deficiency) because slowly dividing erythrocytes accumulate cytoplasmic components, resulting in larger-than-normal cells. hypothyroidism
chronic obstructive pulmonary disease (COPD)
aplastic anemia
reticulocytosis (commonly from hemolysis or a recent history of blood loss). liver disease because of an increase in circulating phospholipids and cholesterol, which bind on erythrocytes and induce membrane expansion
myeloproliferative disease
myelodysplastic syndrome which most commonly presents with macrocytic anemia
chronic exposure to benzene
pregnancy (most common, and requires no treatment as the person affected will return to normal post-partum)
Certain anti-inflammatory drugs, e.g. salazopyrin, azathioprine. Complications
No complications arise from macrocytosis itself and a prognosis will be determined from its cause. See also
Macrocytic anemia

References


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