Merkel cell carcinoma of the forehead area: a literature review and case report

Background: Merkel cell carcinoma (MCC) is an uncommon, aggressive malignancy of the skin, mostly affecting head and neck area in elderly white patients. Between head/neck sites, face accounts for 61% and forehead accounts for 17% of all face MCCs.

Purpose: We here present a literature review MCC cases arising in the forehead area, published in the English literature in the period 1987-2018, and report a personal observation with a late diagnosis and a treatment out of the current recommendations. The aims of this paper are to provide an up-to-date on MCC arising in the forehead area and to raise awareness about misdiagnosis of this type of lesion mimicking arteriovenous malformations (AVM).

Material and method: Literature review was performed on PubMed and Medline database and "Merkel cell carcinoma (MCC)," "forehead" and "MCC forehead location" were the terms the authors searched for. Patients' data have been drawn from descriptions of single cases and of short case series reports. For each case, data were collected about clinical characteristics, treatment modalities and outcomes. The study has been limited to the clinical features of the disease, excluding etiologic/pathogenic aspects.

Results: Twenty-five patients with forehead MCC have been identified, coming from 20 sources. Nineteen presented a locoregional disease and 6 had an advanced pathology. TNM classification was reported in only two cases lacking for the other available data. Patients presented at mean age of 66 years with solitary or multiple nodules or dome-shaped/hemispherical mass, rarely ulcerated. Mean size of tumors was 1.13 cm of max diameter. Previous or concurrent malignancies or immune-hematologic disorders (AIDS) were often associated. At first investigation, lesion was often mistaken for other malignant or benign processes and, then, diagnosis was generally late. Some type of preoperative biopsy was performed in 3 patients, while the others had only a postoperative microscopic study of specimen. Initial treatment consisted in 6 cases (24%) in a not further specified about extent and width of margins local excision of the primary lesion, while a wide resection was reported in only 3 cases (12%). Surgical treatment of involved lymph-nodes was performed in 3 cases (12%). Six patients underwent radiotherapy for locoregional or distant recurrences. Mortality and overall survival rate at five years were 28% and 24%, respectively. Spontaneous regression was observed in 3 patients (12%).

Case report: Personal observation concerned an 82-year-old woman presenting with a forehead periorbital 5 × 5 cm red-bluish mass. The erythematous lesion was erroneously diagnosed as hemangioma on the base of color, the absence of any signs of malignancy, an angio CT indicating a hypervascular tissue and a FNA cytology (FNAC) lacking of malignant cells. The mass was excised as a benign lesion with about 1 cm margins extent without searching larger edges. Postoperative radiotherapy was offered to the patient after histology report, but she refused. After 4 months from surgery, she had a parotid metastasis and died from the illness in spite of platinum-based chemotherapy.

Conclusions: This study confirms the aggressiveness of forehead MCC, comparable with that of other face similar tumors. Personal case suggests that the deceitful benign feature of lesion may mimic an AVM and that FNAC may be misleading and diagnostic failure worsen prognosis. Our experience suggests that in the face smaller than 2-3 cm margins resection may increase the risk of locoregional recurrence. Therefore, postoperative wide-field irradiation should be ever delivered, after forehead MCC surgery, not only when clear margins are unattainable or involved with tumor, but also when negative microscopic edges are documented and residual cancer is thought not persist in the tumor bed. Orbit irradiation seems to be not dangerous for the eye.