Abstract
A 51-year-old Thai woman presented with bilateral leg edema and painful left inguinal mass for 6 months. Physical examination revealed matted bilateral inguinal lymph nodes up to 9 cm in size. Otherwise, physical examinations including skin were unremarkable. The result of the lymph node incisional biopsy is consistent with that of metastatic melanoma. The extensive investigation demonstrated multiple intra-abdominal and inguinal lymph nodes without detectable primary tumor. Palliative radiation and conventional chemotherapy were prescribed. The CT scan between treatments showed that the response was stable disease, but the following CT scan demonstrated a gradual decrease in size from August 2012 to November 2017 including the lesions outside radiation fields. Moreover, she developed vitiligo during a follow-up visit. The previous data reported the median overall survival among the patients who were treated with conventional chemotherapy ranging from 9.1 to 9.3 months and whose 5-year survival was less than 10%. This case represented a metastatic melanoma of unknown primary who achieved a durable response by conventional treatment. The clinical features including nodal-only disease, vitiligo, and abscopal effect of radiation were considered to be the favorable factors.
Highlights
Malignant melanoma is an uncommon skin malignancy accounting for about 4% of skin cancer [1, 2]
This case report represents a patient with metastatic melanoma of unknown primary with durable response by conventional chemotherapy and palliative radiation
The aforementioned hypotheses of unknown primary including an immunological response that leads to spontaneous regression of primary tumor, unrecognized primary tumor, and the occurrence of malignant ectopic nevus cells in the lymph node itself can be considered the etiology of melanoma of unknown primary (MUP) in this patient, who denied previous removal of cutaneous lesion [2, 8, 9]
Summary
Malignant melanoma is an uncommon skin malignancy accounting for about 4% of skin cancer [1, 2]. An incidence rate of melanoma is increasing worldwide but varies between different studies ranging from 0.3 to 3.6% [1] depending on the predominant skin type and geographical location. Most of the literatures in the different geographic regions demonstrated better overall survival of MUP than of MKP [2, 5, 6]. A 5-year overall survival of MUP before the era of the immune checkpoint inhibitor was reported to range from 8 to 18% [3, 4, 7]. The most common metastatic site is the lymph node and GI tract [2, 3]. This study was aimed at reporting a patient with metastatic melanoma of uncertain primary who achieved durable response longer than expected after being treated with conventional treatments
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