Merkel cell carcinoma

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Merkel cell carcinoma
Diagnosis in short

Merkel cell carcinoma. H&E stain.

LM neuroendocrine nuclear features (round nucleus, small nucleoli/no nucleolus, stippled chromatin), usually scant cytoplasm, usually small (~3x resting lymphocyte), often in sheets
LM DDx small cell carcinoma, cutaneous Ewing sarcoma, Burkitt lymphoma, other small round blue cell tumours
IHC Merkel cell polyomavirus +ve, CK20 +ve (perinuclear dot-like), CD56 +ve, TTF-1 -ve, CK7 -ve
Site skin

Clinical history +/-immunosuppressed/immunoincompetent
Prevalence rare
Prognosis poor
Merkel cell carcinoma
External resources
Wikipedia merkel cell carcinoma

Merkel cell carcinoma, abbreviated MCC, is an uncommon aggressive form of skin cancer.

General

Features:[1]

  • Rare.
  • Aggressive course/poor prognosis.
  • Neuroendocrine-like.[2]

Etiology:

  • Most caused by Merkel cell polyomavirus.[3][1]
  • Immunocompromised/immunosuppressed (e.g. organ transplant recipients).

Microscopic

Features:[4]

  • Neuroendocrine nuclear features - round nucleus, small nucleoli/no nucleolus, stippled chromatin - key feature.
  • Typically medium size cells ~3x resting lymphocyte.
    • May be small or large.
  • Architecture: nests, sheets or trabeculae.
  • Scant cytoplasm.
  • Abundant mitoses. †
  • +/-Nuclear moulding.
    • Nuclei of adjacent cells conform to one another.
  • +/-Tumour infiltrating lymphocytes. ‡

Notes:

  • † >10 mitoses/HPF = poor prognosis - definition suffers from HPFitis.[5]
  • ‡ May be associated with a worse prognosis.[5]
  • Merkel cell carcinoma lymph node metastases is difficult to diagnose with routine stains; use of IHC stains are advised.[5]
  • Arise from the epidermis - very rarely in situ.[6]

DDx:

Images

www:

IHC

Features:

  • CK7 -ve.
  • CK20 +ve (perinuclear dot-like).[7]
  • CAM5.2 +ve (dot-like pattern).
  • CD56 +ve.
  • AE1/AE3 +ve.
  • Merkel cell polyomavirus +ve ~85% of cases.[8]

Others:

  • TTF-1 -ve.
  • NSE +ve.[6]
  • PAX5 +ve.[9]

EM

See also

References

  1. 1.0 1.1 Calder, KB.; Smoller, BR. (May 2010). "New insights into merkel cell carcinoma.". Adv Anat Pathol 17 (3): 155-61. doi:10.1097/PAP.0b013e3181d97836. PMID 20418670.
  2. Pulitzer, MP.; Amin, BD.; Busam, KJ. (May 2009). "Merkel cell carcinoma: review.". Adv Anat Pathol 16 (3): 135-44. doi:10.1097/PAP.0b013e3181a12f5a. PMID 19395876.
  3. Feng, H.; Shuda, M.; Chang, Y.; Moore, PS. (Feb 2008). "Clonal integration of a polyomavirus in human Merkel cell carcinoma.". Science 319 (5866): 1096-100. doi:10.1126/science.1152586. PMID 18202256.
  4. Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 491. ISBN 978-0781765275.
  5. 5.0 5.1 5.2 URL: /2011/SkinMerkelCell_11protocol.pdf http://www.cap.org/apps/docs/committees/cancer/cancer_protocols/2011/SkinMerkelCell_11protocol.pdf. Accessed on: 28 March 2012.
  6. 6.0 6.1 Ferringer, T.; Rogers, HC.; Metcalf, JS. (Feb 2005). "Merkel cell carcinoma in situ.". J Cutan Pathol 32 (2): 162-5. doi:10.1111/j.0303-6987.2005.00270.x. PMID 15606676.
  7. Leech, SN.; Kolar, AJ.; Barrett, PD.; Sinclair, SA.; Leonard, N. (Sep 2001). "Merkel cell carcinoma can be distinguished from metastatic small cell carcinoma using antibodies to cytokeratin 20 and thyroid transcription factor 1.". J Clin Pathol 54 (9): 727-9. PMID 11533085.
  8. Jung, HS.; Choi, YL.; Choi, JS.; Roh, JH.; Pyon, JK.; Woo, KJ.; Lee, EH.; Jang, KT. et al. (Oct 2011). "Detection of Merkel cell polyomavirus in Merkel cell carcinomas and small cell carcinomas by PCR and immunohistochemistry.". Histol Histopathol 26 (10): 1231-41. PMID 21870327.
  9. Jankowski, M.; Kopinski, P.; Schwartz, R.; Czajkowski, R. (Nov 2014). "Merkel cell carcinoma: is this a true carcinoma?". Exp Dermatol 23 (11): 792-4. doi:10.1111/exd.12490. PMID 25040178.
  10. Gil-Moreno, A.; Garcia-Jiménez, A.; González-Bosquet, J.; Esteller, M.; Castellví-Vives, J.; Martínez Palones, JM.; Xercavins, J. (Mar 1997). "Merkel cell carcinoma of the vulva.". Gynecol Oncol 64 (3): 526-32. PMID 9062165.