Subungual desmoplastic melanoma in an aboriginal woman

Non-infectious skin disease in Indigenous Australians

The burden of non-infectious skin disease in the Indigenous Australian population has not been previously examined. This study considers the published data on the epidemiology and clinical features of a number of non-infectious skin diseases in Indigenous Australians. It also outlines hypotheses for the possible differences in the prevalence of such diseases in this group compared with the general Australian population. There is a paucity of literature on the topic but, from the material available, Indigenous Australians appear to have a reduced prevalence of psoriasis, type 1 hypersensitivity reactions and skin cancer but increased rates of lupus erythematosus, kava dermopathy and vitamin D deficiency when compared to the non-Indigenous Australian population. This article profiles the prevalence and presentation of non-infectious skin diseases in the Indigenous Australian population to synthesise our limited knowledge and highlight deficiencies in our understanding.

Desmoplastic melanoma: a diagnostic trap for the unwary

Desmoplastic melanoma (DM) is an uncommon type of spindle cell melanoma in which the malignant cells are separated by collagen fibres or fibrous stroma. DM is prone to misdiagnosis because of unfamiliarity with its often bland appearance and dissimilarity to other conventional types of melanoma. It displays variable cytological atypia, cellularity and stromal fibrosis and more often than not has an accompanying atypical junctional component. Neurotropism is a common associated feature (in at least 30% of cases) and when it occurs such tumours are termed 'desmoplastic neurotropic melanomas' (DNM). The neurotropism may be perineural or intraneural and often extends beyond the desmoplastic component. In addition, some DMs show evidence of neural differentiation ('neural transformation'). DM may also present as a recurrence or occasionally as a metastasis from other types of melanoma. A high index of suspicion and knowledge of its often subtle morphological appearance are necessary to avoid misdiagnosis.

Desmoplastic melanoma of the nail

Desmoplastic melanoma represents a variant of melanoma that is difficult to diagnose because 71% of patients have amelanotic skin lesions. In the acral region of the limbs, the clinical diagnosis is more difficult, especially in cases in which there are not clear, rapidly growing, pigmented nail streaks. Histopathological identification of desmoplastic melanoma is confusing because of the intense fibrous reaction in the dermis and minimal, atypical melanocytic proliferation at the dermal-epidermal junction. For these reasons, it is still misdiagnosed unfortunately as a variety of entities, including simple scar, fibrohistiocytic neoplasms, neural tumors, and superficial fibromatoses-with potentially devastating consequences. In equivocal cases, the use of immunohistochemistry (in particular S-100 and neuron-specific enolase) may be helpful in establishing the diagnosis. Because of the high local recurrence rate for desmoplastic melanoma of the finger, amputation is recommended in an effort to gain effective tumor control. Lymph node dissection may be reserved for patients with positive axillary nodes.

Longitudinal melanonychia

BACKGROUND

Ungual melanoma is the most serious disease affecting the nail. The majority start with a longitudinal brown streak in the nail.

OBJECTIVE

To outline the different nail pigmentations, their differential diagnoses, treatment, and prognosis.

METHOD

Clinical and histologic evaluation of dark nail pigmentations.

CONCLUSION

Brown to black nail pigmentation may be due to different coloring substances of exogenous and endogenous origin. Exogenous pigmentations usually are not streaky or do not present as a stripe of even width with regular borders. Bacterial pigmentation, most commonly due to Pseudomonas aeruginosa or Proteus spp., have a greenish or grayish hue and the discoloration is often confined to the lateral edge of the nail. Subungual hematoma may result from a single heavy trauma or repeated microtrauma which often escapes notice. The latter is usually found on the medial aspect of the great toe. Although oval in shape, it commonly does not form a neat streak. Melanin pigmentation in the form of a longitudinal streak in the nail is due to a pigment-producing focus of melanocytes in the matrix. Neither the color intensity nor the age of the patient are proof of benignity or malignancy although subungual melanomas are very rare in children and malignant longitudinal melanonychia is usually wider than 5 mm. Hutchinson's melanotic whitlow, nail dystrophy, and a bleeding mass strongly suggest malignancy. Treatment is as conservative as possible in order to keep the tip of the digit; once the melanoma is completely removed, amputations have not been shown to prolong the disease-free survival time.