Lymphocytes with irregular, hair-shaped, fringe- or shredlike extended cytoplasmic contour are a diagnostic challenge not rarely encountered in blood smear samples. The difficulty consists in deciding whether an artefact, a reactively changed lymphocyte or hair-cell leukemia (HCL) is involved. The morphological principle applies: Diagnostically, the hair-like lymphocyte is a hairy matter. Not every lymphocyte with hairlike cytoplasmic projections is a hair cell.
The occurrence of irregular cell contours especially in B lymphocytes is physiologically and electron microscopically well documented.