Merkel Cell Carcinoma of Unknown Primary Origin

Abstract

Background Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor of the skin. MCC from an unknown primary origin (MCCUP) can present a diagnostic and therapeutic challenge. We describe our single-institution experience with the diagnosis and management of MCCUP presenting as metastases to lymph nodes. Methods After institutional review board approval, our institutional database spanning the years 1998–2010 was queried for patients with MCCUP. Clinicopathologic variables and outcomes were assessed. Results From a database of 321 patients with MCC, 38 (12%) were identified as having nodal MCCUP. Median age was 67 years, and 79% were men. Nodal basins involved at presentation were cervical (58%), axillary/epitrochlear (21%), or inguinal/iliac (21%). CK20 staining was positive in 93% of tumors tested, and all were negative for thyroid transcription factor-1. Twenty-nine patients (76%) underwent complete regional lymph node dissection (LND): 3 had LND alone, ten had LND and adjuvant radiotherapy, and 16 underwent LND followed by chemoradiotherapy. Definitive chemoradiotherapy without surgery was provided to six patients (16%), while radiotherapy alone was provided to three (8%). Recurrence was observed in 34% of patients. Median recurrence-free survival was 35 months. Ten patients (26%) died, five of disease and five of other causes. The median overall survival was 104 months. Conclusions Nodal MCCUP is a rare disease affecting primarily elderly white men. Recurrence is observed in approximately one-third of patients, with a 104 month median overall survival after a multimodal treatment approach consisting of surgery along with adjuvant chemotherapy and radiotherapy in the majority of patients.

Merkel cell carcinoma of lymph node with unknown primary has a significantly lower association with Merkel cell polyomavirus than its cutaneous counterpart

“…One recent study revealed that the nodal Merkel cell carcinoma with an unknown extranodal primary had a lower recurrence rate and a less-aggressive clinical course, compared with the cutaneous Merkel cell carcinoma with nodal metastasis, with a median overall survival of B104 months in the nodal cases. 34 Another more recently published study showed that the overall 2-year survival of nodal Merkel cell carcinoma patients was significantly improved vs matched stage IIIB cutaneous Merkel cell carcinoma (76.9-36.4%). 35 …”

Neuroendocrine Merkel cell nodal carcinoma of unknown primary site: Management and outcomes of a rare entity

“…A significant proportion of MCCUP patients (12.2%, 11/90) had a history of a previously or concurrent treated malignancy (eight basal cell carcinomas, one prostate cancer, three patients with chronic lymphocytic leukaemia), two patients were transplant recipients and another three patients were carriers of HIV. In the immunosupressed population an earlier median onset of the disease at 52 years (37-61) was observed [3,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Almost all evaluable patients presented with clinically palpable non-tender lymph nodes-IIIB disease.…”

“…Inguinal and axillary lymph node areas were initially involved in 40% (36/90) and 17.7% (16/90) of cases, respectively. Lesions ranged in colour from red, pink to blue of flesh-coloured, sometimes with a shiny surface which may mislead to a basal cell carcinoma diagnosis [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Characteristics of all patients are summarised in Table 1 and are displayed in details in Table 2.…”

The diagnostic utility of Merkel cell polyomavirus immunohistochemistry in a fine needle aspirate of metastatic Merkel cell carcinoma of unknown primary to the pancreas

“…Yet about 4%-14% of MCCs manifest as nodal or metastatic disease without a detectable primary tumor. [4][5][6] Pancreatic involvement by MCC is rare with 19 reported cases in the literature. [7][8][9][10][11][12][13][14][15][16][17][18][19] To date, only 8 cases have been diagnosed by endoscopic ultrasound-guided fine-needle aspiration cytology (EUS-FNA).…”