diffuse idiopathic pulmonary neuroendocrine cell hyperplasia : a possible carcinoid precursor

neuroendocrine cells may also proliferate in the bronchiolar
walls without forming tumors, a condition referred to as diffuse
idiopathic pulmonary neuroendocrine cell hyperplasia
(dipnech). 211 histologically, multifocal, patchy collections
of neuroendocrine cells may involve the full circumference
of the bronchiolar walls and form tumorlets or small
carcinoid tumors. the proliferative cells in this condition are
considered to be benign but because the disorder gives rise to
carcinoid tumors, it is considered a premalignant condition.
to date, more aggressive forms of lung carcinoma, including
sclc, have not been associated with dipnech. the condition
may cause an obliterative bronchiolitis that is often a
presenting symptom. it has also been described in association
with hypoxic childhood pulmonary emphysema, tachypnea
of infancy, and adult dyspnea. 212–214 there is currently no
effective treatment.
peripheral airway lesions : adenocarcinoma and
its precursors in this chapter, we use the term peripheral
airway lesions to refer to tumors and premalignant conditions
predominantly arising from airway epithelium distal to the
terminal bronchiolar and alveolar epithelium. most but not
all adenocarcinomas of the lung arise in the peripheral airways
and are divided into invasive adenocarcinoma, which is distinguished
by a fibrous stromal response around individual
tumor cell nests, bronchioloalveolar carcinoma, which grows
exclusively along the alveolar surfaces and does not invade stromal
tissues, and the putative adenocarcinoma precursor lesion
atypical adenomatous hyperplasia (aah).
the incidence of adenocarcinoma is rising. 108 this cell
type:jenis now represents over 30% of primary lung malignancies.
although adenocarcinoma is associated with smoking, the association
is weaker than for squamous cell carcinoma or small
cell carcinoma and a large subset of adenocarcinomas occur
in never-smokers. this histological type:jenis is the most common
type:jenis seen in women and in nonsmokers. 215
emerging evidence suggests and indicates that peripheral
adenocarcinomas may arise from different progenitor lesions
than squamous carcinoma as discussed later. during the past
2 decades, the existence of stepwise sequential morphological
changes corresponding to the progression from atypia to carcinoma
has been described in the peripheral lung. the prognostic
significance of histology in small early lesions is increasingly
better understood. moreover, the increasing sensitivity of
imaging technology during the past several years has allowed
for the detection of smaller lesions in previously inaccessible
peripheral airways. all this has created a pressing need for accurate
classification of the peripheral airway lesions.