Table of Contents
Merkel cell carcinoma – low magnification
Poorly defined and infiltrative dermal infiltrate
Infiltrate composed of monotonous and uniform blue cells with numerous mitoses
Arrangement in cords (linear pattern) or nests (clusters)
Merkel cell carcinoma
LEGEND
Small monotonous blue cells
Multiple mitoses
Merkel cell carcinoma
Infiltrates can be nested in pattern and may mimic, at low magnification, the islands of basal cell carcinoma. However, Merkel cell carcinoma lacks retraction artifacts and displays more pronounced cellular atypia and mitotic activity.
Positive for neuroendocrine granules (chromogranin and synaptophysin)
Positive for EMA (Epithelial Membrane Antigen), NSE (Neuron-Specific Enolase), and neurofilaments
Positive for CK-20
Negative for S-100
TTF-1 (Thyroid Transcription Factor 1) is a useful marker to exclude metastasis from small cell lung carcinoma in the differential diagnosis of small blue cell tumors in histopathology (as TTF-1 is typically negative in Merkel cell carcinoma)
Merkel cell carcinoma
LEGEND
Monotonous cells with scant cytoplasm
Open chromatin with salt-and-pepper appearance
- Presence of mitoses
Merkel cell carcinoma
Infiltrates can be nested in pattern and may mimic, at low magnification, the islands of basal cell carcinoma. However, Merkel cell carcinoma lacks retraction artifacts and displays more pronounced cellular atypia and mitotic activity.
Neurofibroma
Infiltrates can be nested in pattern and may mimic, at low magnification, the islands of basal cell carcinoma. However, Merkel cell carcinoma lacks retraction artifacts and displays more pronounced cellular atypia and mitotic activity.
Neurofibroma
LEGEND
Monotonous cells with scant cytoplasm
Open chromatin with salt-and-pepper appearance
Presence of mitoses
