Vulva, vagina & female urethra
Other carcinomas
Merkel cell carcinoma

Topic Completed: 1 January 2015

Minor changes: 17 August 2020

Copyright: 2002-2020,, Inc.

PubMed Search: Merkel cell carcinoma vulva

Priya Nagarajan, M.D., Ph.D.
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Cite this page: Nagarajan P. Merkel cell carcinoma. website. Accessed October 24th, 2020.
Definition / general
  • First described as an entity in 1972 as "trabecular carcinoma of skin" (Arch Dermatol 1972;105:107); renamed in 1980
  • Patients with MCC are at higher risk to develop neoplasms of hepatobiliary tract, salivary glands, non-Hodgkin lymphoma
  • Commonly coexists with chronic lymphocytic leukemia
  • Merkel cell carcinoma (MCC) of vulva first reported in 1984 by Bottles et al. (Obstet Gynecol 1984;63:61S) although extremely rare at this site
  • Vulvar MCC is considered more aggressive than at other cutaneous sites; this may reflect delayed diagnosis and higher stage but only limited case reports are available to confirm
  • Synonym: primary cutaneous neuroendocrine carcinoma
  • More common in elderly Caucasian population
  • Frequently affects sun exposed parts of body, especially head and neck (J Cutan Pathol 2010;37:20)
  • Median age at diagnosis in immunocompetent patients: 70 years
  • Median age at diagnosis in immunocompromised patients: 53 years
  • Incidence is steadily increasing
  • Labia majus, labium minus, paraclitoral, posterior fourchette, Bartholin gland
  • May contiguously involve vaginal introitus
Clinical features
  • Rapidly growing reddish purple subcutaneous nodule, otherwise usually asymptomatic
  • Ulceration of overlying skin in some cases
  • May present with lymph node metastases, without a vulvar mass
  • Diagnosis requires histologic examination
Radiology description
Prognostic factors
  • Unpredictable prognosis but poor outcome is seen with high stage at diagnosis (based on sentinel lymph node status, presence of in transit or satellite lesions, distant metastasis) and in immunosuppressed patients (Cancer Treat Rev 2013;39:421, J Am Acad Dermatol 2013;68:425)
  • MCPyV negative MCCs may be more aggressive than MCPyV positive tumors
Case reports
  • Surgical: wide local resection with 1 - 3 cm margins; partial, hemi or radical vulvectomy with regional lymph node dissection (Semin Diagn Pathol 2013;30:234)
  • Conventional chemotherapy: neoadjuvant and adjuvant
  • Adjuvant radiotherapy
  • Immunomodulators / immune stimulators: in clinical trial
Gross description
  • Cut sections reveal a variegated tan yellow tumor with dark hemorrhage admixed with necrosis
Microscopic (histologic) description
  • Usually centered in dermis; extensive deeper invasion is not uncommon
  • Only rarely epidermal involvement (epidermotrophism or in situ component)
  • Growth patterns are solid, trabecular, nested, infiltrative
  • Central necrosis is common in tumors with solid growth pattern
  • MCC is a small round blue cell tumor, composed of monomorphous cells with scant, almost indiscernible cytoplasm and round to oval or polygonal hyperchromatic nuclei with dispersed chromatin and inconspicuous nucleoli
  • Nuclei often appear to be arranged back to back and may show moulding
  • Mitoses and apoptotic bodies are frequent
  • Lymphovascular invasion is common
  • Rarely associated with squamous cell carcinoma in situ and benign adnexal tumors
  • Rarely squamous or glandular differentiation
Microscopic (histologic) images

Contributed by Priya Nagarajan, M.D., Ph.D.

Medium power

High power


Mitoses, apoptosis

Central necrosis

Solid and small infiltrative nests

Infiltrative pattern

Plasma cells


Lymphovascular invasion










Positive stains
Negative stains
Electron microscopy description
  • Sparse, peripherally located dense neurosecretory or core granules, free ribosomes, perinuclear aggregate of intermediate filaments, ill developed intercellular junctions and hemidesmosomes
Molecular / cytogenetics description
  • Loss of 1p, 3p, 4, 5q, 7, 10, 14 (Cancers (Basel) 2014;6:2116)
  • Trisomy of 1, 3q, 5p and 6
  • Mutations in chromosome 4 (PDGFRα gene locus)
  • Loss of RB1
Differential diagnosis
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