- Describe the main lesion. Where is it located? What is the diagnosis?
The mass is composed of nests, cords, and sheets of cells lined by delicate fibrous septa. The cells are round, regular with small uniform nuclei and infrequent mitoses. It is located in the bronchus. It is a carcinoid tumor.
- The patient bled profusely when the lesion was biopsied. Why? Why had he recently developed fever and malaise and how does this relate to his chest x-ray and CT findings?
Carcinoid tumors are extremely vascular and thus often bleed when biopsied. The parenchyma behind the tumor shows abundant neutrophils and thus she has a superimposed pneumonia explaining the symptoms and chest x-ray.
- What is the characteristic feature of these tumors by electron microscopy?
By electron microscopy these tumors show electron dense neurosecretory granules.
- In what other organs do these lesions commonly arise? What is the prognosis of these tumors?
They often arise also in the GI tract, with the appendix being a fairly frequent site. The prognosis is usually excellent, though they may metastasize to regional nodes.
- What is the related neoplasm with a more ominous prognosis? How does it differ histologically?
The most malignant end of the neuroendocrine spectrum is oat cell, or small cell carcinoma of the lung, which has an almost uniformly fatal outcome. The cells are more hyperchromatic with almost no cytoplasm. They show little overall architecture. Nuclear molding (nucleus of one cell wrapping around that of another) is a distinctive feature. Usually the chromatin has a kind of "salt and pepper" look to it.
