Carcinoid

Epidemiology:

• 55y mean (younger than SCLC or LCNEC)
• most common lung tumour in childhood

Common sites:

• central or peripheral lung

Gross features:

• fleshy and homogenous
• circumscribed borders
• central lesions:
• polypoid endobronchial masses
• covered in non-ulcerated bronchial mucosa
• peripheral lesions:
• subpleural
• solitary or multiple
• discrete gray-yellow nodule near the pleura
• typical carcinoid:
• size >= 5 mm diameter distinguishes TC from tumourlets
• atypical carcinoid:
• larger
• higher rate of metastases

Histologic features:

• organoid nesting
• other patterns may occur:
• spindle-cell
• trabecular
• palisading
• rosette-like structures
• papillary
• sclerosing papillary
• glandular
• follicular
• uniform cytologic features (relatively)
• moderate eosinophilic, finely granular cytoplasm
• finely granular chromatin (salt and pepper)
• typical carcinoid:
• inconspicuous nucleoli
• < 2 mitoses per 10HPF
• no necrosis
• atypical carcinoid:
• mitoses 2-10 per 10HPF, OR
• presence of necrosis (small foci centrally within organoid nests)
• nucleoli may be more prominent
• the following are not helpful:
• pleomorphism
• vascular infasion
• cellularity
• associated neuroendocrine cell hyperplasia with or without tumourlets
• tumourlet: < 5 mm diameter distinguishes from TC
• variety of cytologic features may be present:
• oncocytic
• acinic cell-like
• signet ring
• mucin-producing
• melanocytic

Immunophenotype:

Marker:	Sensitivity:	Specificity:
Cytokeratin	> 80% (up to 20% may be neg)
Synaptophysin (strong typically)
Chromogranin (strong typically)
CD56 (N-CAM) (strong typically)
S100 (sustentacular cells maybe)
TTF-1 (variable)	Up to 1/3
CD99	many

Molecular features:

• gradual increase in molecular abnormalities from typical carcinoid to atypical carcinoid to LCNEC or SCLC
• MEN1 gene mutations and LOH at MEN1 (11q13) (65% of sporadic atypical carcinoids)
• Not found in high-grade neuroendocrine tumours
• familial:
• MEN-1

Other features:

• paraneoplastic syndromes:
• carcinoid syndrome
• Cushing’s syndrome
• Acromegaly
• Typical carcinoid:
• Excellent prognosis
• Atypical carcinoid:
• Higher rate of metastases
• Significantly reduced survival (~30%)

References:

• Travis WD. Pathology of Lung Cancer. Clinics in Chest Medicine 2002; 23(1): 65-81.
• WHO blue book 2004