Metastatic Melanomas of the Groin Lymph Nodes without Known Primary Lesion in a Developing Community

Melanoma could present with metastasis from an unknown primary. It is an event reported to happen in 2-3%. In particular, lymph nodes could be the organs involved as reported in a USA case recently. Therefore, the author reports 8 cases obtained from a histopathology data pool situated in a developing community; this idea followed the suggestion of a Birmingham (UK) group, namely, that such a pool promotes epidemiological analysis.


Introduction
In a recent USA case report [1], a 58-year-old Caucasian male presented with a right sided swelling in the inguinal region. It was surgery that revealed it to be due to metastatic melanoma. As no cutaneous lesion was identified by history or physical examination, it was theorized that spontaneous regression was a possibility. Accordingly, it is desirable to publish such cases worldwide. The present cases were documented in a Nigerian community due to following the suggestion made by a Birmingham (UK) group [2], namely, that the establishment of a histopathology data pool promotes epidemiological analysis. The establishment of a Regional Pathology Laboratory in 1970 in Enugu, the capital of the Eastern Region of Nigeria, helped matters, seeing that the author became the pioneer pathologist. Therefore, this investigation concerns the benefitting Nigerian ethnic group, the Igbos or Ibos [3]. In particular, the clinicians working among them were encouraged to send formalin-fixed biopsy specimens complete with notes as to age, sex, complaints and any interesting findings [ Table 1].

Investigation
OO, a 70-year-old man, presented at the University of Nigeria Teaching Hospital, Enugu, with a lump in the right groin of 3 years duration. There was no associated history of ulceration in the drainage area. This was carefully biopsied. The submitted skin ellipse measured 12 x 10 cm and there was a central ulcer. Below

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it, there was a 15 x 5 x 4 cm mass. On section, it was inky black and necrotic in the center. There were solid satellites up to 2 cm across. Microscopy revealed an ulcerated growth undermined by a necrotic melanin forming spindle called growth. There was no junctional activity. Malignant melanoma was diagnosed.

Remarks
As regards both site and structure, the probability is that this is a metastasis. The primary is either healed as is known to occur rarely or hidden in urethra, anus or rectum.

Discussion
In the treatment of melanoma, the standard of cure for palpable groin lymph nodes is dissection [4,5]. This was undertaken in the present series.
Surprisingly, the nearer group is not the groin but the popliteal group in terms of pedal primaries. Therefore, it must have been skipped, a well known mechanism in metastasis [6]. Little wonder that case reports have been recorded lately in terms of the melanoma [7][8][9]. Indeed, the author has personally challenged researchers [10]; they should explain why this is a rarity in lung cancer in which millions of cancer cells necessarily enter the circulation [11].
Perhaps, in the case of melanomas, one is up against a tumor endowed with molecular and genetic diversity [12]. Incidentally, there is even inter-observer variation in the histopathological diagnosis of clinically suspicious pigmented skin lesions [13]. In the circumstances, what is new, asked Evoy's group [14], "in the management of malignant melanoma?" As they answered, "The combination of sentinel lymph node mapping coupled with immunotherapy in node-positive patient may have potential to increase survival." Of course, this concept is a far cry in terms of a developing community!