Skin - Nonmelanocytic tumors
Carcinoma (non-adnexal)
Merkel cell carcinoma

Author: Christopher Hale, M.D. (see Authors page)

Revised: 19 January 2017, last major update June 2012

Copyright: (c) 2002-2017,, Inc.

PubMed Search: Merkel cell carcinoma [title] skin

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Cite this page: Merkel cell carcinoma. website. Accessed February 17th, 2019.
Definition / general
  • Also called neuroendocrine carcinoma of skin
  • Originally called trabecular carcinoma
Clinical features
  • Usually adults or elderly
  • 60% women
  • Face and extremities
  • May be associated with squamous cell carcinoma (in situ or invasive), basal cell carcinoma, eccrine duct-like structures
  • Aggressive
  • Regional nodal metastases are common
  • Distant metastases to liver, lung, bones; also testis or other unusual sites
  • Rarely appears to arise initially in lymph node, probably due to regression of primary skin tumor
  • May derive from Merkel cell in epidermis, derived from neural crest, important for tactile sensation in lower animals
Case reports
  • Wide local resection, regional lymph node resection
  • Radiation therapy and chemotherapy as needed
Clinical images

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Hip lesion

Gross description
  • Nodular or ulcerated red-violet lesion
Gross images

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Breast skin, courtesy of Mark R. Wick, M.D.

Hip lesion

Microscopic (histologic) description
  • Dermal or subcutaneous centered tumor with monotonous round tumor cells and diffuse infiltration of subcutis
  • May have focal trabecular pattern
  • Cells have scant eosinophilic cytoplasmic rim, round and vesicular nuclei with finely granular and dusty chromatin and multiple nucleoli
  • Also apoptotic nuclei and frequent mitotic figures
  • May have vascular stroma with plump endothelial cells
  • Epidermis is usually spared
  • Rarely has leiomyosarcoma or atypical fibroxanthoma-like areas
Microscopic (histologic) images

Images hosted on PathOut server:

Breast skin, courtesy of Mark R. Wick, M.D.






Case of the Week #304

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H&E, 2x

H&E, 10x

H&E, 20x

H&E, 40x

CK20, 40x

NSE, 40x

Images hosted on other servers:

Dermal solar degeneration

Dark epitheliod neoplastic infiltrates

Vague cell borders




Cytology images

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Giemsa stain, COW #414

Cell PAP, COW #414

Cell block - H&E, COW #414

FNA, CK20+ with perinuclear dot like
staining, CD45-, TTF-; flow was CD56+, CD45-

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Paranuclear blue dots, courtesy of Dr. Tim Bracey

Positive stains
Negative stains
Electron microscopy description
  • Dense core neurosecretory granules and tightly packed intermediate filaments
  • Well developed desmosomes
Molecular / cytogenetics description
  • Abnormalities in #1, #11, #12
  • 1p35-36 deletion