Minute foci of atypical bronchiolar epithelial hyperplasia that are found multifocally; although now considered benign, they were once believed to be precursors of carcinoma.
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Provided they are not present at the margins, the presence of other neoplastic processes (eg, tumorlets, minute meningothelial nodules, neuroendocrine hyperplasia, atypical adenomatous hyperplasia, squamous dysplasia) does not impact tumor staging.
94) These lesions have been variably designated as sporadic Cajal cell hyperplasia, microscopic GISTs, GIST tumorlets, or "seedling" GISTs.
Carcinoid tumorlets are distinguished from NE hyperplasia by extension beyond the basement membrane of the respiratory epithelia.
First, and the most common setting for multiple tumorlets and NE hyperplasia, is that of chronic lung injury, such as bronchiectasis or fibrosis.
29) Because respiratory compromise develops only in a small subset of patients with NE hyperplasia and tumorlets, the 2004 WHO classification does not require this clinical association in the definition of DIPNECH.
Lastly, NE cell hyperplasia and tumorlets are frequently but not invariably seen in lungs resected for carcinoid tumors (46%-76%), both in the vicinity and away from the tumor.
In a classic clinical setting of a patient presenting with respiratory symptoms and pathologic findings of diffuse NE hyperplasia and tumorlets in the absence of other pathologic findings, the diagnosis of DIPNECH is straightforward.
Potential Etiologies of Constrictive Bronchiolitis (a) Post lung transplantation Post bone marrow transplantation Healed infection, especially adenovirus infection Drug reactions Healed injury from exposure to fumes and toxins Collagen vascular disease, especially rheumatoid arthritis As a component or complication of: Bronchiectasis Cellular bronchiolitis Asthma Chronic bronchitis Cystic fibrosis DIPNECH or carcinoid tumorlets Inflammatory bowel disease-associated small airways disease Idiopathic Abbreviation: DIPNECH, diffuse idiopathic neuroendocrine cell hyperplasia.
As they progress to carcinoid tumorlets and tumors they appear as small, well-demarcated, gray-white nodules resembling "miliary bodies.
2] Granular cell tumors (GCTs) presumably arise from enlargement of tumorlets.
8] It is suggested that GCTs and their tumorlet precursors derive from pituicytes and thus are astrocytic in nature and therefore a form of glioma.