Metastatic melanoma of unknown primary in the temporalis muscle

Abstract

Melanomas are aggressive cancers that present as cutaneous, mucosal and ocular lesions with the ability to metastasise widely. There are, however, occasions where lesions are found in distant sites such as lymph nodes, viscera and subcutaneous tissues without clinically apparent skin involvement. This is known as metastatic melanoma of unknown primary (MUP). Its presentation in skeletal muscle is rare, and the available literature is sparse. This article presents an 85-year-old woman with a MUP presenting in the right temporalis muscle, which was diagnosed with the aid of the ultrasound-guided core biopsy. The melanoma deposit was successfully excised, and no recurrence was identified. The patient is now under close follow-up.

Diagnostic dilemma in a patient with upper arm mass with history of breast cancer and melanoma

“… 8 Two mechanisms underlying this radiological appearance have been proposed: 1) paramagnetism of stable free radicals in melanin and 2) methemoglobin in nonacute haemorrhage of the tumour. 9 …”

Metastatic malignant melanoma of unknown primary in temporalis muscle

“…Malignant melanoma is an aggressive tumour of melanocytes, which are derivatives of the neural crest cells [ 1 ], and its common presentations as cutaneous, mucosal or ocular lesions allow for its classification [ 3 ]. MUP is defined as a histologically confirmed melanoma found in skin, subcutaneous or visceral tissues or lymph nodes, with no manifestation of a primary lesion [ 3 ]. MUPs comprise up to 6% of diagnosed melanomas, 60% of which are present in lymph nodes, and reports of intramuscular lesions as in this case are rare [ 3 ].…”

“…MUP is defined as a histologically confirmed melanoma found in skin, subcutaneous or visceral tissues or lymph nodes, with no manifestation of a primary lesion [ 3 ]. MUPs comprise up to 6% of diagnosed melanomas, 60% of which are present in lymph nodes, and reports of intramuscular lesions as in this case are rare [ 3 ]. To our knowledge, this is only the fourth such report [ 3–5 ]; as in Mercer and Deveraj’s [ 4 ] case, a diagnosis was reached upon excision and investigation failed to identify a primary.…”

“…Furthermore, patients with MUP and lymph node disease have similar or better survival in comparison with stage-matched patients with melanoma of known primary. Treatment depends upon the staging of the lesion and can range from surgical excision to oncological treatment with radiotherapy and chemotherapy [ 3 ] but should be the same as that for stage-matched patients with melanoma of known primary.…”