Superficial spreading melanoma
Nodular melanoma
Acral lentiginous melanoma
(from C. Urso: Lesioni melanocitiche cutanee. Guida alla diagnosi istologica, Suppl.2/96 Derm. Amb.1996)
Lentigo maligna melanoma
Melanoma of the skin is a tumor which virtually can arise in every cutaneous region. Four types of melanoma occur.
Superficial spreading melanoma is a flat or barely raised, unevenly pigmented, brown, black or pink-gray, asymmetric, with possible white areas of depigmentation and irregular borders. It is generally larger than 1 cm and may be large several centimeters and presenting one or more nodules. Nodules may be entirely or partially pigmented, sometimes achromic. Histologically, it is a large and asymmetric lesion. Its invasive component is composed of round atypical melanocytes,epithelioid, spindle shaped or nevus cell-like, infiltrating the dermis and the subcutaneous fat. Cells are arranged in defined nests, alveolar structures, or solid masses. Melanin is contained in tumor cells in a variable amount, in superfial areas or in deep ones; it may also be lacking (achromic melanoma). In early invasive tumors, atypical melanocytes infiltrate the papillary dermis in nests or alveolar structures; subsequently malignant cells tend to fill the entire thickness of the papillary dermis, and then they infiltrate the reticular dermis. Sometimes, the tumor has a polipoid esophytic architecture, often with epidermal ulceration. The epidermis adjacent to the invasive component shows a histologic features of melanoma in in situ: numerous round atypical melanocytes, single or in nests, infiltrate all the epidermal layers (pagetoid infiltration); Nests are pleomorphic, confluent, variable in size and in shape. At the periphery of the tumor, melanocytic proliferation is less marked towards the normal skin. However, at least 3 rete ridges are involved. At the base of the neoplasm and below the in situ component, a dense lichenoid limphocytic infiltrate may be seen. Sometimes in some zones the melanocytic proliferation may disappear, being replaced by inflammatory infiltrate, fibrosis, melanophages and blood vessels (regression).
Lentigo maligna melanoma is a large macule, brown-black, irregularly pigmented, with one or more nodules, occurring in photoexposed areas (face,neck,extremities) of elderly people. It is the invasive phase of lentigo maligna. It comprises about 5% of all melanomas. Histologically, the lesion is asymmetric, composed of atypical, mostly splindle shaped, melanocytes, infiltrating the dermis and sometimes the subcutaneous fat. Cells, variable in size and in shape, form irregular fascicles. Melanin amount is quite variable. The adjacent epidermis is hypotrophic and flattened and show an increased number of atypical melanocytes, often spindle shaped, as solitary units at the dermoepidermal junction, involving pilosebaceous follicles. Rarely, melanocytes form small nests, sometimes some malignant cells are seen in the suprabasal layers. The superficial dermis shows solar elastosis, melanophages and a dense lichenoid lymphocytic infiltrate.
Nodular melanoma is a cutaneous nodule, sometimes polipoid and/or ulcerated, black, bluish or pink; the adjacent skin is not pigmented. Histologically, it is composed of round atypical melanocytes, sometimes pagetoid, with ample clear or weakly pink cytoplasm, sometimes containing fine granules of melanin. Malignant cells, arranged in alveolar structures or solid masses, infiltrate the dermis deeply, sometimes the subcutaneous fat. Sometimes, the tumor is limited to the papillary dermis (level III). Neoplastic nuclei are large, atypical, hyper- or hypochromatic, and vesicular (empty nuclei), with a prominent eosinophilic nucleolus. Mitoses and cellular necrosis may be present. Melanin is variable, in superficial and in deeper zones, and may be absent (achromic melanoma). At the base of the tumor or among neoplastic cells a lymphocytic infiltrate may be observed. The epidermis is infiltrated by numerous atypical melanocytes and may be ulcerated; neoplastic cells tend to infiltrate toward bottom; pagetoid infiltration may be lacking or minimal. The adjacent epidermis is not involved by malignant cells; however, involved rete ridges are less than 3.
Acral lentiginous melanoma is a large black-brown, irregularly pigmented flat lesion, which may present nodules, sometimes ulcerated. It may show grey zones due to the thickness of the horny layer or irregualr white areas of regression. The involved sites are the plantar region of the foot, the palmar region of the hand or subungueal tissues. Histologically, the lesion is large and asymmetric, formed by atypical melanocytes, often spindle shaped, infiltrating the dermis deeply, sometimes the subcutaneous fat. Cells may be epithelioid or nevus cell-like and contain fine granule of melanin.
Melanin is contained in tumor cells in a variable amount, in superfial areas or in deep ones; it may also be lacking (achromic melanoma). At the base of the tumor or among neoplastic cells a lymphocytic infiltrate may be observed.
Desmoplasia is frequent, solar elastosis absent. The epidermis, markedly hyperplastic with tall epidermal papillae, is infiltrated by atypical melanocytes and may be ulcerated. The adjacent epidermis shows an increased number of round atypical melanocytes. Cells may be pagetoid, spindle shaped or dendritic, and are located at the dermoepidermal junction, mostly as single units; upper layers are generally involved.
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The other pages
page 13: Merkel cell carcinoma
page 14: Basal cell carcinoma
page 15: Melanoma in paediatric age