Primary Neuroendocrine (Merkel Cell) Carcinoma

 Especially lung, which are TTF-1(+), CK20(-)

• Small cell melanoma

• Lymphoma

Clinical Photograph of MCC
Clinical photograph of Merkel cell carcinoma (MCC) shows a well-circumscribed, erythematous dermal nodule. (Courtesy J. Wu, MD.)

MCC Involving Superficial Dermis
The superficial dermal portion of this tumor shows enlarged, crowded and markedly atypical-appearing basaloid cells with several large, atypical mitotic figures image easily identified.

Higher Magnification of MCC With Lymphatic Invasion
High magnification of the superficial dermal portion of this tumor shows enlarged, atypical basaloid cells with several frankly atypical mitotic figures image. Invasion of a superficial lymphatic vessel is also seen image.

High Magnification of MCC
Nuclear clearing image is often seen in MCC, a feature not seen in basal cell carcinoma or most other small round blue cell tumors. Note the numerous apoptotic bodies image and mitotic figures image.



• Merkel cell carcinoma (MCC)


• Cutaneous neuroendocrine carcinoma

• Primary small cell carcinoma of skin

• Trabecular carcinoma


• Malignant proliferation of cutaneous neuroendocrine cells


Infectious Agents

• Recent studies have shown strong link to infection with polyomavirus
image Merkel cell polyoma virus infection is found in > 90% of cases by PCR studies

• Associated with immunosuppression
image Organ transplant and HIV(+) patients have much higher incidence

Cell of Origin

• Postulated to represent malignant transformation of cutaneous neuroendocrine (Merkel) cells or pluripotent stem cells, but this remains speculative



• Incidence
image Rare

– < 500 cases/yr in USA

• Age
image Typically in elderly patients (> 65 yr old)

• Sex
image M > F (2.5:1)

• Ethnicity
image Caucasians much more commonly affected than other races


• Sun-damaged skin

• Usually head and neck or extremities


• Dermal nodular or plaque-like mass lesion
• Rapidly enlarging dermal mass lesion

image May be ulcerated &/or hemorrhagic

Natural History

• Aggressive tumors with high incidence of local recurrence, lymph node, and distant metastasis

• Clinical staging should include imaging studies, especially chest and abdominal CT scans


• Surgical approaches
image Complete and wide excision to ensure complete local removal

image Consideration may be given to sentinel lymph node (SLN) biopsy

– However, SLN positivity does not seem to be very sensitive for regional lymph node involvement, as many patients progress to distant metastases

• Adjuvant therapy
image Radiotherapy is generally used and may lead to remission in some cases

image Chemotherapy is less effective and does not prolong overall survival


• High incidence of recurrence (up to 30%) and metastasis (up to 75%)
• Overall prognosis is poor

image Death due to disease is high, even with treatment

image Worse prognosis associated with advanced age, head and neck location, large size, and immunosuppression


General Features

Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Primary Neuroendocrine (Merkel Cell) Carcinoma

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