You answered: Basal cell carcinoma
Sorry, that is INCORRECT
The correct diagnosis is: Merkel cell carcinoma
- Poorly cohesive population of small blue cells, uniform in appearance. Some clustering may be seen
- High N/C ratios, rounded nuclei, powdery chromatin (best appreciated on fixed specimens), inconspicuous nucleoli, scant cytoplasm
- "Blue buttons" (perinuclear cytoplasmic aggregates of intermediate filaments) in cytoplasm, but not specific and is also seen in small cell carcinoma of the lung
- Immunohistochemistry shows characteristic perinuclear dot-like positivity for CK20, positive for neurofilaments, negative for TTF-1 and CK7 (useful in distinction from small cell carcinoma of lung). It is also negative for LCA (distinction from lymphoma)
- This is consistent with a diagnosis of Merkel Cell Carcinoma
- Merkel cell carcinoma is a rare primary neuroendocrine carcinoma of the skin
- Most occur in the head and neck area or buttocks of elderly patients
- Clinically, this tumour is nodular with a reddish or violaceous hue, centred in the dermis.
- They are usually locally agressive and can metastasize
- Treatment involves wide resection of the primary site and regional lymph node dissection; radiation therapy can be used as an adjunct, and chemotherapy has been employed for metastatic tumours
- The major differential diagnoses are small cell carcinoma of the lung and malignant lymphoma
- Merkel cell carcinoma cells are more uniform (with no irregular or spindle-shaped cells), with minimal moulding, and show a more dispersed cell pattern when compared to small cell carcinoma of the lung
- Presence of true tissue aggregates and lack of lymphoglandular bodies aid in differentiating Merkel cell carcinoma from malignant lymphoma
- Basal cell carcinomas typically show large tight clusters of atypical basaloid cells, with no nuclear moulding. Cells characteristically palisade at the periphery on tissue histology
BACK TO IMAGES
DeMay RM. The Art & Science of Cytopathology. Chicago: ASCP Press, 1996; 605, 630-1.
Rosai J. Ackerman's Surgical Pathology. Mosby, 8th Edition, 1996; 166-8.
Case 12 Histology - Merkel Cell Carcinoma