Which histologic findings are characteristic of pediatric nasal polyps?

Updated: Oct 25, 2019
  • Author: John E McClay, MD; Chief Editor: Ravindhra G Elluru, MD, PhD  more...
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Answer

Histologically, nasal polyps are characterized by a pseudostratified ciliated columnar epithelium, thickening of the epithelial basement membrane, and few nerve endings. The stroma of nasal polyps is edematous. Vascularization is poor and lacks innervation, except at the base of the polyp. Authors report either hyperplasia of the seromucous glands or almost absent or rare glands when comparing the polyps to the inferior or middle turbinate. Hyperplasia of the gland can cause cystically dilated and degenerated glands containing inspissated mucous.

Eosinophil cells are the most commonly identified inflammatory cell, occurring in 80-90% of polyps. Eosinophils, which are found in the polyps of patients with bronchial asthma and allergy, contain granules with toxic products (eg, leukotrienes, eosinophilic cationic protein, major basophilic protein, platelet-activating factor [PAF], eosinophilic peroxidases, other vasoactive substances and chemotactic factors). These toxic factors are responsible for epithelial lysis, nerve damage, and ciliostasis. Specific granule protein, leukotriene A4, and PAF apparently are responsible for the mucosal swelling and hyperresponsiveness.

Eosinophils in the peripheral blood and in normal nasal mucosa usually last 3 days. In a cell culture of nasal polyps, eosinophils were present at least 12 days. This delayed apoptosis of eosinophils is mediated, in part, by blockage of the Fas receptors, typically with proteases that help begin the process of cell death.

Delayed apoptosis is also mediated by an increase in interleukin (IL)-5, IL-3, and granulocyte-macrophage colony-stimulating factor (GM-CSF) secreted by T cells, which help sustain the eosinophil from death. Glucocorticoids seem to help reduce polyps or polypoid reactions in patients with tissue eosinophilia, possibly, in part, by inhibiting IL-5.

Another inflammatory cell, the neutrophil, occurs in 7% of polyp cases. This type of polyp occurs in association with CF, primary ciliary dyskinesia syndrome, or Young syndrome. These polyps do not respond well to corticosteroids because they lack corticosteroid-sensitive eosinophils. Degranulated mast cells are present. Degranulation presumably occurs in a non–immunoglobulin (Ig) E–mediated fashion. Increased numbers of plasma cells, lymphocytes, and myofibroblasts also occur.


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