Squamous Melanocytic Tumour at an Unusual Site: An Uncommon Case and Literature Review

Barbara Barbosa*, Salvador J. Diaz-Cano and Alexandre Abramavicus

Squamous Melanocytic Tumour at an Unusual Site: An Uncommon Case and Literature Review.

We herein present a case report of a 60-year-old male patient
diagnosed with squamous-melanocytic tumour in his anal region,
comprised of two intermingled different phenotypic lesions.

This dual tumour is quite uncommon and could potentially be challenging
on both diagnose and also management. It is the first case reported on this location,
moreover, the lack of consensus for these lesions makes it difficult to classify them.

We reviewed the literature of similar SMT’s and discussed its histogenesis.
As they are rare, their biological behavior and potential metastasis remain unclear.
Therefore, close follow-up is advised.

Anal squamous cell carcinoma is a rare condition. Of all cancers of the lower gastrointestinal tract, anal squamous cell carcinoma accounts for 4% of the total.

Likewise, primary malignant melanoma of the anorectal area are
quite infrequent and only represents 0.4%-1.6% of all melanomas and
less than 1% of anal canal tumours.

Not surprisingly, a combination of both is an exceeding rare tumour.
Our case is the first SMT case reported in the anorectal region.
The literature review shows nineteen SMT reported cases.

Most of them located on the head and neck and none in the perineal or
genital areas. The biological behavior remains unclear and albeit
eighteen cases have not shown any further malignant report there
is one case with SMT metastasis.

There is no definitive risk factor  for SMT lesions although
some of them have been linked to previous burn and solar conditions.

Histological examination showed on low-power magnification a
fairly well-circumscribed epidermal tumour with endophytic proliferation
displaying striking dark pigment within it.

The tumour was confined to the basal membrane.
There was no evidence of invasive malignancy.

Dermatol Open J. 2020; 5(1): 6-9. doi: 10.17140/DRMTOJ-5-139