CLINICAL HISTORY:

Signs and symptoms:  The patient stated the lesion had no discharge and was neither tender nor pruritic. She denied any history of similar lesions. She also denied fever, night sweats, heat/cold intolerance, and weight fluctuation.

Previous Treatment:  Upon initial presentation to her primary care physician, a diagnosis of an irritated epidermal cyst was made and she was prescribed three courses of azithromycin. Incision and drainage by her PCP failed to express any culturable material or cause the lesion to involute.

Other information:  A 3 mm punch biopsy was taken from lesion. The biopsy findings prompted a complete radiological workup, including MRI and CT scans of the head and neck.

PHYSICAL EXAM:

Clinical examination revealed a 1.2 cm erythematous, slightly movable, firm nodule with a central crust located in the left malar area, directly below the infraorbital prominence. No pre- or post-auricular, cervical or supraclavicular lymphadenopathy was appreciated. Evaluation of the head, neck, nares, and oral mucosa revealed no other suspicious lesions.

LABORATORY TESTS:

MRI studies of the head demonstrated a 1.7 x 2.0 cm nodule in the left malar region, with subcutaneous and underlying skeletal muscle invasion. No hypervascularity or bone involvement was observed. A second focus of similar signal, measuring 2.4x1.2x1.7 cm, was seen inferior and slightly medial to the right submandibular gland. Additionally, there was significant lymphadenopathy detected bilaterally in the submandibular chains. CT evaluation also confirmed the secondary focus noted in the right submandibular region, at the level of the hyoid. Chest x-rays were unremarkable.

DERMATOHISTOPATHOLOGY:

Histologic examination of the punch biopsy revealed variously sized and shaped aggregates of neoplastic cells with finely granular nuclei and scant cytoplasm. The cells displayed an infiltrating growth pattern throughout the dermis, subcutis, and skeletal muscle. Furthermore, many mitoses and necrotic cells were noted. Immunohistochemical stains were positive for CK20, CD45, chromogranin A, and focally positive for low-molecular weight keratin subtypes. Stains for S-100 antigen were negative.
Right sentinel lymph node biopsy showed elaborate branching papillae with ovoid, hypochromatic nuclei, nuclear grooves, and intranuclear inclusions. Numerous psammoma bodies were also present. The biopsy showed thyroglobulin immunoperoxidase positivity.

DIFFERENTIAL DIAGNOSIS:

1.   Squamous cell carcinoma with nodal metastasis
2.   Squamous cell carcinoma with metastatic papillary thyroid carcinoma
3.   Merkel cell carcinoma with nodal metastasis
4.   Merkel cell carcinoma with metastatic papillary thyroid carcinoma
5.   None of the Above

SCROLL DOWN FOR ANSWER AND DISCUSSION.

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 effects elderly patients and demonstrates no predilection for sex. Clinically, the lesions typically manifest on the head and neck areas, but they can also arise on 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:

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, a total thyroidectomy with selective lymph node dissection was accomplished

REFERENCES:

1. Tang CK, Toker C. Trabecular carcinoma of the skin: an ultrastructural study. Cancer. 1978;42:2311-2321.
2. Toker C. Trabecular carcinoma of the skin. Arch Dermatol. 1972;105:107-110.
3. Shaw JH, Rumball E. Merkel cell tumour: clinical behaviour and treatment. Br J Surg. 1991;78:138.
4. Yiengpruksawan A, Coit DG, Thaler HT, Urmacher C, Knapper WK. Merkel cell carcinoma: prognosis and management. Arch Surg. 1991;126:1514.

Additional Comment:

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