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Journal of Clinical Oncology, Vol 25, No 24 (August 20), 2007: pp. 3785-3786 © 2007 American Society of Clinical Oncology. DOI: 10.1200/JCO.2007.12.3091
Merkel Cell Carcinoma As a Solitary Metastasis to the TestisDepartment of Surgery, Urology Service, Walter Reed Army Medical Center, Washington, DC
Department of Pathology, Walter Reed Army Medical Center, Washington, DC A 70-year-old white man with a past medical history significant for Merkel cell carcinoma (MCC) of the right gluteal region presented with a solitary right testicular mass. The patient's original skin lesion was 2 cm in size and treated with wide local excision and sentinel lymph node biopsy after negative metastatic work-up 15 months before presentation. Both inguinal and femoral sentinel lymph nodes were positive, prompting a complete inguinal and femoral lymph node dissection where all nodes were negative (0 of 18). He refused further treatment with chemotherapy or radiation. A testicular ultrasound was obtained that revealed a well-circumscribed, hypoechoic solid mass in the lower pole of the right testis measuring 1.4 x 1.9 x 1.8 cm. Metastatic work-up with computed tomography of the chest, abdomen, and pelvis, positron emission tomography (PET), liver-associated enzymes, beta human chorionic gonadopropin, alpha fetoprotein, and lactate dehydrogenase were negative. An uncomplicated right radical orchiectomy was performed, and pathologic examination revealed a 2.4 x 1.5 x 1.4 cm tan, pink, well-circumscribed, lobulated mass in the lower pole of the testis (Fig 1; testis bisected, exhibiting 2.4-cm circumscribed mass.). Microscopically, the tumor infiltrated around seminiferous tubules and exhibited a solid, organoid, and trabecular growth pattern. Extensive lymphatic invasion was present. The neoplastic cells were monotonous, small, and round with evenly distributed chromatin, inconspicuous nucleoli, and abundant mitotic figures (> 100/10 high-power fields; Fig 2; top: hematoxylin and eosin, 600x; bottom, immunohistochemistry for CK20, 600x). The immunoprofile was similar to the primary cutaneous tumor. The neoplastic cells were immunopositive for neuroendocrine markers (chromogranin/synaptophysin) and cytokeratin 20 (perinuclear dot positivity), and were negative for cytokeratin 7, S-100, prostate-specific antigen, and carcinoembryonic antigen (Fig 2B). Ki-67 was positive in approximately 50% of the neoplastic cells. The pathologic findings supported the diagnosis of metastatic MCC. At the time of publication, the patient is 6 months from his orchiectomy and has no evidence of disease.
MCC is a rare neuroendocrine tumor of the skin that has a poor prognosis. It occurs most commonly in white people and appears on skin of sun-exposed areas. Although uncommon, its incidence in recent years is increasing with a rise of 8% per year since 1986.1 The rapid growth of these tumors makes metastasis common, with only 50% of patients having localized disease at time of diagnosis.2 The most common metastatic sites are skin, lymph nodes, liver, lung, bone, and brain (Table 1). 3
Stage at initial diagnosis has significant impact on outcome. The mainstay of therapy is surgical excision with a 2-cm margin and sentinel lymph node biopsy or formal regional lymphadenectomy. In the absence of nodal disease, the survival rate at 5 years is 75% to 97%. If lymph node–positive disease is documented, survival at 5 years is 25% to 52%.2,4 Radiation can be administered to the region of the primary lesion in stage I and II disease (regional lymph nodes only), whereas chemotherapy is reserved for stage III disease (distant metastasis). Fifty-five percent to 79% of patients experience recurrence, with most doing so within 1 year.5 MCC metastasizing to the genitourinary tract is rare. There have only been six previous cases of testicular metastasis documented in the literature.6-10 To our knowledge, this is the first report of a solitary testicular lesion without concomitant diffuse disease. Interestingly, metastasis to the testis can occur from any primary tumor site. Those described in the literature are upper lip, left elbow, right gluteal region, and forearm in two cases.7,6,9,10 It is also noteworthy that MCC thrives in the immunocompromised patient, suggesting that immune surveillance is important both to prevention and spread of the disease.5 The presence of narrow tight junctions and myoid cell layer producing a blood testis barrier combined with the absence of T lymphocytes in the testis due to Fas ligand binding may allow micrometastatic disease to grow unchecked in this location. As described previously, the incidence of MCC is growing at an alarming rate. Furthermore, five cases (including this case) of testicular metastasis have been documented in the past 5 years.6,8,9,10 In contradistinction, there were only two reports before 2001.7 This may represent an epidemiologic phenomenon, a change in tumor biology, or a result of increased survivorship that allows for growth in unsuspected locations. Regardless, genital exams are not routinely done in surveillance of MCC and present imaging may not include this region. Because surgical resection is a mainstay of cure, finding disease in an amenable location for extirpation is clinically relevant. Our recommendation is to counsel patients on self examination, incorporate examinations into practice patterns, and further report metastatic disease to the testis in order to document trends. AUTHORS’ DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST The author(s) indicated no potential conflicts of interest.
REFERENCES
1. Alam M: Management of Merkel cell carcinoma: What we know. Arch Dermatol 142:771-774, 2006 2. Agelli M, Clegg LX: Epidemiology of primary Merkel cell carcinoma in the United States. J Am Acad Dermatol 49:832-841, 2003[CrossRef][Medline] 3. Voog E, Biron P, Martin JP, et al: Chemotherapy for patients with locally advanced or metastatic Merkel cell carcinoma. Cancer 85:2589-2595, 1999[CrossRef][Medline] 4. Allen PJ, Bowne WB, Jaques DP, et al: Merkel cell carcinoma: Prognosis and treatment of patients from a single institution. J Clin Oncol 23:2300-2309, 2005 5. Goessling W, McKee PH, Mayer RJ: Merkel cell carcinoma. J Clin Oncol 20:588-598, 2002 6. Gleason JM, Kohler TS, Monga M: Merkel cell carcinoma metastatic to testis. Urology 67:423, 2006[CrossRef] 7. Ro JY, Ayala AG, Tetu B, et al: Merkel cell carcinoma metastatic to the testis. Am J Clin Pathol 94:384-389, 1990[Medline] 8. Rufini V, Perotti G, Brunetti M, et al: Unsuspected testicular metastases from Merkel cell carcinoma: A case report with therapeutic implications. Am J Clin Oncol 27:636-637, 2004[CrossRef][Medline] 9. Schwindl B, Meissner A, Giedl J, et al: Merkel cell carcinoma –a rarity in the urogenital tract. Onkologie 29:326-328, 2006[CrossRef][Medline] 10. Tummala MK, Hausner PF, McGuire WP, et al: A sanctuary site in Merkel cell carcinoma. J Clin Oncol 24:1008-1009, 2006
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Copyright © 2007 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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