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INTRODUCTION

A 60-year-old white male had a 6-cm central lung mass biopsied by core needle biopsy.

He smoked two packs of cigarettes per day for 40 years and has had a coronary stent placed.

The magnetic resonance imaging (MRI) of the brain shows 2 subcentimeter metastases.

A positron emission tomographic (PET) scan shows a liver mass and rib lesions.

His serology shows a sodium level of 120 mEq/L.

Learning Objectives

  1. What is the new World Health Organization (WHO) classification for small cell lung cancer?

  2. What are the markers distinguishing small cell from non–small cell lung cancer?

  3. What are the types of neuroendocrine tumors found in the lung?

Recognition of the distinct biological behavior of small cell carcinoma from that of non–small cell carcinoma has been long established. Therefore, the characterization of small cell carcinoma has proven to be very important as it has therapeutic as well as prognostic implications. However, the presence of other tumors with overlapping morphological, ultrastructural, and immunohistochemical features has complicated this endeavor.

PREINVASIVE LESIONS

Neuroendocrine Hyperplasia and Tumorlets

The spectrum of preinvasive neuroendocrine lesions encompasses conditions of several associations and clinical presentations. However, the histomorphologic features are mostly similar with only a few distinguishing features.

There are conditions that are associated with neuroendocrine cell hyperplasia but the mechanism of action is poorly understood. The chronic conditions of inflammation and fibrosis as in patients with chronic obstructive pulmonary disease have a tendency to harbor small foci of neuroendocrine proliferation. These are usually incidental findings encountered when the lung is sampled for other reasons. In resections for carcinoid tumors, other foci of neuroendocrine proliferation are present and could represent a “field defect” similar to that of atypical adenomatous hyperplasia (AAH) and adenocarcinoma. The spectrum of neuroendocrine tumors in their progressive pattern is outlined (Table 7-1).

TABLE 7-1Neuroendocrine Proliferations and Tumors of the Lung

Diffuse Idiopathic Neuroendocrine Cell Hyperplasia

Diffuse idiopathic neuroendocrine cell hyperplasia is an uncommon condition in which the airways are circumferentially involved by a proliferation of neuroendocrine cells underneath the bronchial epithelium (Figure 7-1). The origin of these cells is believed to be from Kulchitsky cells, which normally reside as individual cells in this location. In about half of the patients, the neuroendocrine hyperplasia ...

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