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Journal of Cancer Research and Therapeutics, Vol. 6, No. 3, July-September, 2010, pp. 353-355 Case Report Bilateral renal metastases in a case of Merkel cell carcinoma Seema Medhi1, Nilendu C Purandare2, Sumeet G Dua2, Sumeet Gujral3 1 Department of Radiodiagnosis, Tata Memorial Hospital, Mumbai - 12, India Correspondence Address:Sumeet G Dua, Bio-Imaging Unit, Tata Memorial Hospital, Mumbai - 12, India , duasum@gmail.com Code Number: cr10085 PMID: 21119275 DOI: 10.4103/0973-1482.73365 Abstract Merkel cell carcinoma is a primary neuroendocrine carcinoma of the skin. It is a highly aggressive tumor which commonly metastasizes to lymph nodes, liver, lung and bone. The diagnosis is based on histology and immunohistochemistry. Renal metastasis, with sparing of other common sites of hematogenous spread (lung and liver), is a unique feature of this case.Keywords: Kidney/renal metastases, merkel cell carcinoma, skin tumor Introduction Merkel cell carcinoma, by virtue of its inherent aggressiveness, often spreads to the draining nodes, with frequent metastatic dissemination to the lung, liver and bones. This report describes bilateral renal metastases from a Merkel cell carcinoma, never documented before with a note on the role of imaging in staging of Merkel cell cancer. Case Report A 64-year-old man presented with a skin nodule in the right thigh that had progressively increased in size over a period of three months. On clinical examination, this nodule was pink, painless and measured about 3 cm in diameter. The patient had no other symptoms and rest of the physical examination was normal. There was no inguinal adenopathy. An excisional biopsy of the nodule was performed. Histopathology revealed round cell tumor with the cells arranged in nests, cords and trabeculae. The tumor cells showed stippled chromatin without nucleoli. High degree of mitosis and apoptosis was seen. Overlying skin was infiltrated by the tumor. On immunohistochemistry, the tumor cells showed dot like positivity for cytokeratin-20 (CK-20) and also expressed epithelial membrane antigen (epithelial markers) and neuron-specific enolase. Tumor cells were negative for S-100 protein and HMB45 (melanoma markers), chromogranin and synaptophysin (neural markers), Mic2, calponin and Bcl-2 (PNET and synovial sarcoma markers). A diagnosis of Merkel cell carcinoma was rendered. A computed tomography (CT) scan of the thorax, abdomen and pelvis was performed to look for distant metastases. There were no lung nodules or liver metastases; however, multiple focal necrotic masses were noted in both kidneys [Figure - 1]. The renal masses showed perinephric extension and heterogenous contrast enhancement with hypodense areas within, suggesting an aggressive pathology. The right sided renal mass showed infiltration of the right lobe of the liver. Ultrasound-guided fine needle aspiration of bilateral renal masses revealed a cellular round cell tumor [Figure - 2] which was compatible with metastases from a known Merkel cell carcinoma of thigh. In view of metastatic disease, patient was offered palliative chemotherapy. Discussion Merkel cell carcinoma (MCC) is a rare, aggressive primary neuroendocrine carcinoma of the skin. It is also known as primary small cell carcinoma or trabecular cell carcinoma. In 1972, Toker described five cases of trabecular cell carcinoma of skin and attributed its origin to sweat glands. [1] However, in 1978, Tang and Toker, on electron microscopy discovered dense core granules characteristic of Merkel cells and other neuroendocrine cells, indicating an origin from the Merkel cell. [2] Merkel cell is a specialized mechanoreceptor situated in the basal cell layer of the epidermis. [3] The name Merkel cell carcinoma was suggested by De Wolf-Peeters et al, in 1980. [4] Most cases of MCC are reported in the elderly, with a notable high incidence in subjects with AIDS or with a prior history of organ transplantation. [5] The classical clinical presentation is a rapidly expanding, 1-2 cm sized, asymptomatic, red/pink nodule seen on sun-exposed skin. The common sites of involvement are head, neck, lower and upper extremities. [6] Spread to the draining nodes is a frequent finding and is associated with a higher local recurrence following surgery. [7] Distant metastases are seen in about half of the cases particularly involving the lung, liver and bone and correlates with adverse prognosis. [8] The diagnosis of MCC is based on histological and immunohistochemical analysis of biopsied tissue. The nodule is often localized to the dermis and can spread superficially or deep to involve the epidermis and subcutaneous tissues, respectively. Classical histological features include a triad of vesicular nuclei with tiny nucleoli, and numerous mitoses and apoptosis, with accompanying lymphovascular invasion. [9] MCC is categorized into a group of small blue cell tumors which includes other tumors such as small-cell lung cancer, lymphoma, neuroblastoma, Ewing′s sarcoma, melanoma and basal-cell carcinoma. [8] The diagnosis is based on the characteristic dot-like positivity for CK-20 expressed by MCCs on immunohistochemistry, although neuroendocrine (neurone-specific enolase, synaptophysin, chromogranin) and other cytokeratin (CAM 5.2) markers are also expressed. [10] Surgical excision is the mainstay of treatment, with adjuvant radiotherapy being offered to almost all patients. Chemotherapy is generally reserved for palliation of metastatic disease. [11] Unusual sites of distant metastases from MCC described in literature include urinary bladder, [12] prostate [12] and pancreas. [13] An extensive review of literature revealed a solitary reference of renal metastases from MCC, [14] where the patient presented with renal metastasis two years after surgery and radiotherapy for the primary tumor in the sacral region emphasizing the rarity of this finding. However in our case, bilateral renal metastases were detected on CT scan during the initial staging workup. Moreover, there were no clinical signs or symptoms attributable to the renal masses. Bilateral renal masses as seen in our case could also have been bilateral renal cell carcinomas in a case of a multisystem disorder like von Hippel Lindau disease (VHL). Radiologically, these findingsth can be very similar and differentiation between metastases and primary renal carcinomas would be difficult. The more common features of VHL like pancreatic cyts, renal cysts were not seen. Clinical features due to cerebellar and retinal hemangioblastomas seen very often with VHL were also absent though no imaging of the brain was performed to rule out these conditions. In view of the known primary disease, an FNA cytology was attempted from the renal masses which revealed metastatic MCC. The finding of bilateral renal masses with an aggressive appearance on imaging should always raise the possibility of secondary renal involvement particularly in a patient with a known malignancy, even though the primary (Merkel cell carcinoma in our case) may show a very low propensity of renal metastases. The presentation of a patient of primary MCC with bilateral renal metastases without involvement of local nodes or other commonly encountered sites of distant metastases is a unique feature of this case. This report also brings to focus the value of imaging in unmasking the common as well as rare sites of metastases in uncommon tumors like MCC. References
Copyright 2010 - Journal of Cancer Research and Therapeutics The following images related to this document are available:Photo images[cr10085f1.jpg] [cr10085f2.jpg] |
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