CORRECT DIAGNOSIS:
Metastatic Papillary Thyroid Carcinoma in a Patient with Merkel Cell Carcinoma
DISCUSSION:
Merkel cell carcinoma (MCC) is a rare, yet highly aggressive cutaneous malignancy of controversial origin. As its name implies, Merkel cell carcinoma (MCC) was initially thought to originate from Merkel cells, slow adapting touch receptors located directly above the basement membrane. While some authors believe MCC is derived from the neural crest, most likely Merkel cells, others identify its origin as the malignant differentiation of a dermal pluripotent stem cell.1,2 Trabecular carcinoma, anaplastic carcinoma of the skin, and neuroendocrine tumor have all been used as synonyms of MCC and reflect the general lack of consensus regarding this entity’s histogenesis.
MCC is a rare tumor that primarily affects elderly patients and demonstrates no predilection for sex. Clinically, the lesions typically manifest on the head and neck areas, but they can also arise in other areas of the body. The usual appearance is a pink-red or violaceous, firm, dome-shaped solitary nodule that grows rapidly. Ulceration can occur. Due to the violaceous, hemorrhagic appearance of the tumor, the differential diagnosis includes abscess, angiosarcoma, squamous cell carcinoma, hemangioma, or lymphoma.
The prognosis for MCC is poor because of its aggressive nature and tendency for lesions to recur. Two recent studies have shown that the survival rates of patients with MCC are comparable to those of patients with melanoma.3,4 MCC patients have also demonstrated a high incidence of coexisting neoplasms. This case report augments the growing evidence supporting the association of MCC and concurrent neoplasms and re-emphasizes the need for a thorough workup in patients with MCC.
TREATMENT:
The actual treatment for this patient: The patient underwent a total elliptical excision with 3 mm margins. Intraoperatively, a sentinel lymph node biopsy was completed. Post-operatively, external beam irradiation was administered to the surgical site and associated scar region. A cumulative radiotherapy dose of 5,600 cGy was given over a course of 28 fractions, using a 7 MeV electron. Additionally, total thyroidectomy with selective lymph node dissection was accomplished
REFERENCES:
Tang, C. K., & Toker, C. (1978). Trabecular carcinoma of the skin: An ultrastructural study. Cancer, 42(6), 2311–2321. https://doi.org/10.1002/1097-0142(197812)42:6<2311::AID-CNCR2820420611>3.0.CO;2-A [PMID: 697407]
Toker, C. (1972). Trabecular carcinoma of the skin. Archives of Dermatology, 105(1), 107–110. https://doi.org/10.1001/archderm.1972.01620130079011 [PMID: 5068876]
Shaw, J. H., & Rumball, E. (1991). Merkel cell tumour: Clinical behaviour and treatment. British Journal of Surgery, 78(1), 138. https://doi.org/10.1002/bjs.1800780134 [PMID: 1986503]
Yiengpruksawan, A., Coit, D. G., Thaler, H. T., Urmacher, C., & Knapper, W. K. (1991). Merkel cell carcinoma: Prognosis and management. Archives of Surgery, 126(13), 1514. https://doi.org/10.1001/archsurg.1991.01410220028005 [PMID: 1749077]
