Aggressive Merkel Cell Carcinoma in a Liver Transplant Recipient

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine tumor derived from the nerve-associated Merkel cell touch receptors.¹ It typically presents as a solitary, rapidly growing, red to violaceous, asymptomatic nodule, though ulcerated, acneform, and cystic lesions also have been described.² Merkel cell carcinoma follows an aggressive clinical course with a tendency for rapid growth, local recurrence (26%–60% of cases), lymph node invasion, and distant metastases (18%–52% of cases).³

Several risk factors contribute to the development of MCC, including chronic immunosuppression, exposure to UV radiation, and infection with the Merkel cell polyomavirus. Immunosuppression has been shown to increase the risk for MCC and is associated with a worse prognosis independent of stage at diagnosis.⁴ Organ transplant recipients represent a subset of immunosuppressed patients who are at increased risk for the development of MCC. We report a case of metastatic MCC in a 67-year-old woman 6 years after liver transplantation.

Case Report

A 67-year-old woman presented to our clinic with 2 masses—1 on the left buttock and 1 on the left hip—of 4 months’ duration. The patient’s medical history was remarkable for autoimmune hepatitis requiring liver transplantation 6 years prior as well as hypertension and thyroid disorder. Her posttransplantation course was unremarkable, and she was maintained on chronic immunosuppression with tacrolimus and mycophenolate mofetil. Six years after transplantation, the patient was observed to have a 4-cm, red-violaceous, painless, dome-shaped tumor on the left buttock (Figure 1). She also was noted to have pink-red papulonodules forming a painless 8-cm plaque on the left hip that was present for 2 weeks prior to presentation (Figure 1). Both lesions were subsequently biopsied.

Figure 1. Clinical appearance of Merkel cell carcinoma lesions on the left buttock and left hip on initial presentation.

Microscopic examination of both lesions was consistent with the diagnosis of MCC. On histopathology, both samples exhibited a dense cellular dermis composed of atypical basophilic tumor cells with extension into superficial dilated lymphatic channels indicating lymphovascular invasion (Figure 2). Tumor cells were positive for the immunohistochemical markers pankeratin AE1/AE3, CAM 5.2, cytokeratin 20, synaptophysin, chromogranin A, and Merkel cell polyomavirus.

Figure 2. Merkel cell carcinoma tumor consisted of dense cellular dermis composed of atypical basophilic tumor cells with extension into superficial dilated lymphatic channels indicating lymphovascular invasion (H&E, original magnification ×20).

Total-body computed tomography and positron emission tomography revealed a hypermetabolic lobular density in the left gluteal region measuring 3.9×1.1 cm. The mass was associated with avid disease involving the left inguinal, bilateral iliac chain, and retroperitoneal lymph nodes. The patient was determined to have stage IV MCC based on the presence of distant lymph node metastases. The mass on the left hip was identified as an in-transit metastasis from the primary tumor on the left buttock.

The patient was referred to surgical and medical oncology. The decision was made to start palliative chemotherapy without surgical intervention given the extent of metastases not amenable for resection. The patient was subsequently initiated on chemotherapy with etoposide and carboplatin. After one cycle of chemotherapy, both tumors initially decreased in size; however, 4 months later, despite multiple cycles of chemotherapy, the patient was noted to have growth of existing tumors and interval development of a new 7×5-cm erythematous plaque in the left groin (Figure 3A) and a 1.1×1.0-cm smooth nodule on the right upper back (Figure 3B), both also found to be consistent with distant skin metastases of MCC upon microscopic examination after biopsy. Despite chemotherapy, the patient’s tumor continued to spread and the patient died within 8 months of diagnosis.

Figure 3. Metastatic Merkel cell carcinoma on the left groin (A) and on the right upper back (B) 4 months after initial presentation.