Merkel cell carcinoma with lymph node metastasis in the absence of a primary site: Case report and literature review.

Dec 2012

Zhao M, Meng MB.

Source

Tianjin University of Traditional Chinese Medicine; ; Tianjin Tasly Co. Ltd.;

Abstract 

Merkel cell carcinoma (MCC) is a rare malignant skin neoplasm with the potential for local recurrence, spreading to regional lymph nodes (LNs) and distant metastases. Although it has been identified in various anatomical sites, LN metastatic MCC in the absence of a primary site is extremely rare. The present case reports a 54-year-old male who initially underwent histological examination of a biopsy specimen from the right inguinal LNs. A diagnosis of metastatic small cell carcinoma was made. Nine months later, this diagnosis was changed to MCC with multiple metastases following observation of a tumour mass in the right dorsal thigh. Additionally, in the present study a summary is provided of 23 published cases of MCC with initial LN metastasis in the absence of a primary site, with details of clinical characteristics, natural history and pertinent therapy of this uncommon tumour. The present patient with LN metastatic MCC in the absence of a primary site and the other reported cases demonstrate that although multimodal treatment with surgery, radiotherapy (RT) and chemotherapy provides excellent local control, local recurrence and distant metastases commonly develop in this uncommon tumour. LN metastatic MCC in the absence of a primary site is a highly malignant disease and the role of adjuvant postoperative RT and/or chemotherapy remains to be fully determined.

PubMed

Merkel Cell Carcinoma

Merkel Cell Carcinoma

MD Anderson Cancer Center

Merkel Cell Carcinoma

Merkel Cell Carcinoma (MCC) is a rare skin malignancy which was first described in 1972 by Cyril Toker. However, the name Merkel cell comes from the anatomist who discovered the normal Merkel cell in pig snouts - Friedreich Sigmund Merkel in 1875. Because of the tumor cell characteristics seen under the microscope, the name neuroendocrine carcinoma of the skin is used synonymously with Merkel cell carcinoma.

The true incidence of this cancer is not known, but 400 - 600 cases have been described in the literature. Merkel cell carcinoma is almost exclusively seen in Caucasian people, and most are more than 65 years old. Some of the literature reports that MCC affects men and women equally, but other studies have shown a male predominance. The etiology of this tumor is not clearly defined, but there has been association of MCC to sun exposure. Many of the patients have a history of other basal or squamous cell cancers of the skin, and approximately 10% of the patients will develop a second primary cancer.

Merkel cell carcinoma most commonly occurs in the skin of the head and neck (50%), followed by the extremities and the trunk. The head and neck, cheek, forehead, temple, nose, and upper neck are the most common sites. This tumor is innocuous in appearance - described as a painless, solitary, raised, pink nodule. Most tumors are less than 2 cm when initially discovered. Biopsy is the only way to diagnose MCC. However, the diagnosis is difficult for most pathologists, and requires both the use of the electron microscope and special staining of the cells to differentiate it from other small cell carcinomas.

Merkel cell carcinoma is a very aggressive cancer. Lymph node metastasis occurs early and often. Some studies report palpable lymph nodes at presentation in 45% of patients. However, distant metastasis is rare at presentation. Local and regional recurrence occurs frequently, and is felt to be related to the adequacy of the initial therapy. Distant metastasis occurs in approximately 25% of patients, regardless of therapy.

The current thoughts on treating Merkel cell cancer include both the primary lesion and the regional lymphatics. It is felt that the primary cancer should be surgically removed with negative margins. Studies have shown that surgical treatment alone has a higher rate of local and regional recurrence that those who receive surgical excision and radiation therapy. Thus, after the tumor is removed, 6 weeks of radiation to the surgical site and to the regional lymphatics is recommended. However, despite this aggressive therapy, approximately 40% still develop locoregional recurrence.

It is felt that regardless of therapy, 25 - 35% of patients may ultimately recur. It is felt that the development of locoregional recurrence is a predictor of multiple recurrence and distant metastasis. Thus, it is implied that early locoregional treatment will improve tumor control. However, it is not proven whether locoregional control will affect the rate of distant metastasis and ultimately affect survival.