Melanoma with unknown primary: report and analysis of 24 patients

Abstract

In the literature, there are some papers reporting on patients with metastatic melanoma from an unknown primary lesion (MUP). The pathogenesis of this phenomenon and the prognosis of these patients are still debatable. Therefore, we reviewed our casistics on MUP patients. We identified 24 MUP patients out of all patients registered into a melanoma database from June 1996 to June 2011. The incidence was 1.4%. We compared the survival rate of all patients with MUP stage III-IV with all patients with metastatic melanoma known primary (MMKP) stage III-IV observing a clear survival improvement for MUP patients in front of MMKP patients (p<0.01). In a second instance, we compared stage III MUP patients with only lymph nodal involvement with stage III MMKP patients with only lymph nodal involvement, and again we found statistically significant better survival for MUP patients (p<0.05). In this retrospective study, the number of lymph nodes involved (p=0.8), the sex (p=0.9), and S100 value (p=0.2) were not statistically relevant for prognosis. The better prognosis for these patients is very similar to better survival rate for metastatic melanoma patients and vitiligo. This correlation may be in accord with the hypothesis of a regression of primary lesion by immunological system of the host and also the median age of patients at the time of diagnosis, commonly older than melanoma patients, may correspond to a long period of immunological interferences between the host and the melanoma disease.

Melanoma Characteristics in Patients with a History of UV Tanning Bed Usage

“…Our study found that the average age at biopsy for people who reported tanning bed usage was significantly lower compared to those who had not reported using a tanning bed but that age at biopsy was not found to be significant associated with 5 year OS. Characteristics of tanning bed users in our cohort were consistent with other studies, Caucasian women 1 with a young age at presentation. 2…”

“…No primary site is identified in 1% to 8% of all melanomas. 1 Questions remain about MUP reflecting effective immune clearance of the cutaneous primary lesion, and our finding may implicate a detrimental effect on immune clearance induced by tanning bed exposure. This finding requires further exploration in clinical and basic studies.…”

“…The incidence of melanoma is increasing at a rate greater than any other cancer, 1 possibly due to increasing use of indoor tanning devices. Melanoma is an aggressive skin cancer and an increasingly important public health concern.…”

Unknown Primary Melanoma: Worldwide Survey on Clinical Management

“…MUP is by definition a metastatic melanoma [1] . After Das Gupta et al [3] had first defined MUP criteria, many authors investigated the prognosis of this entity with conflicting results [1,[9][10][11] .…”

Current management of melanoma

“…The overall survival of patients with MUP who present with lymph node involvement or visceral organ disease is no worse than, and is perhaps better than, the overall survival of patients with MKP who have stage III or stage IV disease, respectively. 132,135,136 Adjuvant therapy…”