Histopathologic diagnosis of pigmented lesions of the skin

Metastatic malignant melanoma of palate: A review of literature and report of an unusual case

Oral malignant melanoma is a rare tumor, accounting 0.8to 1.8 % of all oral malignancies. It occurs most commonly in Japanese and Negros. Radical surgery is mainstay of the treatment. Prognosis is very poor with 5 years survival rate. We present a case of malignant melanoma in a 55 years female, metastatizing to liver spleen and vertebrae.

Equine skin tumours in 20 horses resembling three variants of human melanocytic naevi

Melanocytic tumours are important in horses, especially grey horses. Intradermal common melanocytic naevi, cellular blue naevi and combined cellular blue naevi are subgroups of human melanocytic tumours, which have not been reported in horses. In this study, we describe 20 horses with skin tumours similar to these naevi of humans. These tumours represented individual skin masses in male and female horses of different breeds. Tumours resembling human intradermal common melanocytic naevi were noted in 12 horses aged between 2 and 17 years. Seven horses aged between 4 and 15 years developed cutaneous lesions similar to human cellular blue naevi. A combined cellular blue naevus-like tumour was diagnosed in a 20-year-old horse. All tumour types formed expansile, well-demarcated, non-encapsulated, symmetrical masses. Tumours similar to intradermal common melanocytic naevi were composed of nests of round and spindeloid neoplastic cells, often embedded in myxomatous stroma. Lesions resembling cellular blue naevi were formed by intradermal bundles of ovoid to elongated cells separated by collagen fibres. The combined cellular blue naevus-like tumour resembled human cellular blue naevus with in addition, an overlying junctional common melanocytic naevus. Neoplastic cells in all groups contained varying amounts of melanin pigment and were immunopositive for S100. These equine skin tumours differ from the commonly recognized equine melanocytic tumours by their cytomorphological features, random location and the absence of an increased tumour frequency in grey horses. The resemblance of these tumours to three distinct subgroups of human naevi expands the complexity of equine proliferative cutaneous melanocytic lesions.

Doença de Paget pigmentada do mamilo simulando melanoma cutâneo: importância da imuno-histoquímica na diferenciação dessas doenças

A variante pigmentada da doença de Paget mamária é rara, com cerca de 12 casos relatados, e pode mimetizar clínica e histologicamente o melanoma. Como na forma clássica, em geral associa-se à neoplasia da mama acometida, com origem principalmente no carcinoma intraductal que se estende à epiderme através de ducto lactóforo. A fisiopatologia da hiperpigmentação permanece desconhecida. Relata-se o caso de paciente de 49 anos que apresentou lesão pigmentada do mamilo, suspeita de melanoma. O exame histológico não foi suficiente para confirmar o diagnóstico, sendo necessária realização de perfil imuno-histoquímico. Apesar de incomum, o diagnóstico de doença de Paget deve ser lembrado como diferencial de melanoma em lesões pigmentadas dessa região, em ambos os sexos.

Acral-lentiginous naevus of plantar skin

In a consecutive series of 165 plantar naevi, a group of 36 benign naevi with sufficiently distinctive histopathological features to justify their classification as a special entity, here designated acral-lentiginous naevus, was identified. The main morphological features distinguishing the acral-lentiginous naevi from other acral non-lentiginous naevi are: elongation of rete ridges, continuous proliferation of melanocytes at the dermo-epidermal junction, presence of single scattered melanocytes, or less commonly small clusters, within the upper epidermis, poor or absent lateral circumscription, melanocytes with abundant pale cytoplasm and round to oval, sometimes hyperchromatic, nuclei and prominent nucleoli present at the dermo-epidermal junction. Some histological features of acral-lentiginous naevi are similar to those of dysplastic naevi: however, anastomosing rete ridges, cytological atypia and well-formed lamellar fibroplasia are absent. The histopathological criteria to distinguish these naevi from melanoma are: the lack of pagetoid lateral spread, the absence of mitotic activity in the deep dermal component and the evidence of dermal naevocytic differentiation. The identification of this benign acral naevus, that we have identified as the benign counterpart of acral lentiginous melanoma, is important in order to avoid misdiagnoses and consequent under- or over-treatment of doubtful pigmented lesions of acral skin.

Malignant melanoma of the oral cavity--an increasing clinical diagnosis?

Oral malignant melanoma is fortunately a rare lesion. However the actual incidence in the population at present is unknown but may be increasing. The overall prognosis remains poor despite more radical surgery with adjuvant radiotherapy, chemotherapy and immunotherapy. The clinical presentation of oral malignant melanoma can vary widely from a typically pigmented macular or proliferative lesion to a non-pigmented soft vascular tumour; single or multiple, primary or metastatic. Our experience of five patients with malignant melanoma of the oral cavity is presented and the management of such lesions discussed.