Spindle cell melanoma7/4/2023 ![]() ![]() The proportion of the invasive melanoma that is desmoplastic.Mitotic rate – a measure of how fast the cells are proliferating.Margins of excision, the normal tissue around a tumour.Breslow thickness to the nearest 0.1 mm.The pathologist's report should include a macroscopic description of the specimen and melanoma (the naked eye view) and a microscopic description. p75 nerve growth factor is a marker for spindle cell melanoma.HMB-45 and Melan-A are usually negative.Immunohistochemical stains for melanoma may be helpful. Lymphocytic nodular aggregates may be seen in association with desmoplastic melanoma, but are not diagnostic.Nerve infiltration or neurotropism is found in about half of desmoplastic melanomas.There is overlying melanoma in-situ, typically of lentigo maligna type, in approximately 75% of cases.A paucicellular atypical spindle cell proliferation, separated by fibrocollagenous stroma within the dermis or subcutaneous fat.Histopathological features of desmoplastic melanoma include: The pathological diagnosis of melanoma can be very difficult. If the skin lesion is suspicious of desmoplastic melanoma, it should be urgently cut out ( excision biopsy). Atypical or polymorphous vascular pattern.Regression features: scar-like areas, grey dots.Melanocytic features in about 50% (pigmented globules or network).The most frequently observed dermatoscopic features of desmoplastic melanoma are: Dermoscopyĭermoscopy can be helpful in distinguishing desmoplastic melanoma from other skin lesions. Reflectance confocal microscopy may be useful to help guide the site of the biopsy. Depending on the thickness and proportion of desmoplasia within the invasive melanoma, sentinel lymph node biopsy, imaging studies and blood tests may be advised.Īs desmoplastic melanoma is commonly found on the head and neck, and with lentigo maligna, it is possible that if such lesions are only partially biopsied, the desmoplastic melanoma may be missed. Clinical diagnosis is aided by dermoscopy and skin biopsy (usually excision biopsy). Palpation is an important step, as a large majority of desmoplastic melanoma are indurated. A careful clinical history is important, which includes noting previous treatments received for non-resolving lesions. It is essential to diagnose desmoplastic melanoma accurately. What triggers the melanocytes to become malignant is unknown, but it is likely to be a series of changes to DNA. These cells may arise within another type of melanoma or in previously normal-appearing skin. What is the cause of desmoplastic melanoma?ĭesmoplastic melanoma is due to the development of malignant pigment cells (melanocytes) within the dermis. Not uncommonly, desmoplastic melanoma can be mistaken for other benign lesions, such as: What is the differential diagnosis of desmoplastic melanoma? A greater number of colours, especially blue or black.Variable pigmentation – most often skin-coloured or pink, but may also have areas of brown, grey, blue or black.ĭeep invasive melanoma often has the following features:.Irregular or regular borders (more often irregular).Size > 6 mm and often 1–2 centimetres in diameter at diagnosis.Flat or raised papule, plaque or nodule.Firm scar-like consistency with a smooth or irregular surface.It becomes more distinctive in time, often growing over months to years before it is recognised. It is often skin coloured but may be pigmented. It presents as a slowly enlarging area of thickened skin, sometimes described as scar-like. What are the clinical features of desmoplastic melanoma?ĭesmoplastic melanoma is most common on sun-exposed areas of the head and neck (> 50%). Desmoplastic melanoma usually lacks the ABCD melanoma warning signs: Asymmetry, Border irregularity, Colour variation, large Diameter. Previous invasive melanoma or melanoma in situ.The main risk factors for desmoplastic melanoma are: Desmoplastic melanoma is more common in males (65%) than females.It usually occurs in white-skinned individuals.For up to date recommendations, refer to Australian Cancer Council Clinical practice guidelines for the diagnosis and management of melanoma Who gets desmoplastic melanoma?ĭesmoplastic melanoma accounts for about 1% of melanoma in Australia and New Zealand. ![]()
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