Desmoplastic Malignant Melanoma: A Clinicopathologic Analysis of 113 Cases

Department of Dermatology, Hospital de Santa Maria, Universidade de Lisboa, Lisboa, Portugal.
The American Journal of dermatopathology (Impact Factor: 1.39). 06/2008; 30(3):207-15. DOI: 10.1097/DAD.0b013e3181716e6b
Source: PubMed


Desmoplastic melanoma (DM) is a rare variant of spindle cell melanoma, which usually develops in sun-damaged skin of elderly patients. Often the lesion is nonpigmented and frequently mistaken for a nonmelanocytic proliferation, which delays diagnosis and treatment and therefore worsens the prognosis. The spindle shape of neoplastic melanocytes, the prominent desmoplasia, and the frequent neurotropism of neoplastic melanocytes are its most characteristic histopathological features. We have studied the clinicopathologic features of 113 cases of DM. The mean age of the patients was 71.1 years; 48% of the patients were males and 52% were females. The neoplasm was located on the head in 72% of the cases. Malignant melanoma was the initial clinical diagnosis in only 27% of the cases. Histopathologically, all lesions appeared as poorly demarcated neoplasms that involved the entire dermis and often extended into the subcutaneous tissue. The neoplasms were composed of ill-defined fascicles of spindle cells. Desmoplasia was defined as the presence of spindle cells associated with a fibrotic stroma. Fifty-one cases (45%) were classified as "pure DM" when the lesion was entirely desmoplastic, and 62 cases (55%) were considered as "combined DM" when a recognizable desmoplastic component was seen in an otherwise conventional malignant melanoma. In 81% of the cases, an atypical intraepidermal melanocytic component (in situ malignant melanoma) was identified, whereas in the remaining 19% of the cases the intraepidermal component was lacking. Seventy-one percent of the cases were histologically amelanotic, 23% showed a small amount of pigment, and only 6% were heavily pigmented. Neural involvement was identified in 40/113 cases (35%), predominantly in the thickest tumors. Lymphoid nodules, found in 42/113 cases (37%), were significantly more frequent in pure DM than in combined DM (53% vs 24%). The null hypothesis of homogeneity of the "pure" and "combined" subgroups should be rejected (P < 0.002). Solar elastosis, with variable intensity, was seen in 82% of the cases. Mean Breslow thickness was 4.1 mm (4.6/3.7 mm, in the pure/combined subgroups, respectively), median was 4.0 mm (4.0/3.0 mm); Breslow thickness ranged from 0.3 to 11.0 mm, with half of the cases thicker than 4 mm. Only 4% of the cases showed Clark level below IV. The predominant neoplastic cells consisted of spindle-shaped melanocytes in 85% of the cases, whereas the remaining 15% of the cases demonstrated round neoplastic cells forming the main mass of the neoplasm. The mitotic rate of the neoplastic cells was low in 72% of the cases, 23% had an intermediate mitotic rate, and 5% showed a high mitotic rate. On follow-up, 55/113 patients (49%) (with an average of 55 months) demonstrated persistence of the disease. About 4% had local recurrences, 2% of lymph node invasion, 9% systemic metastases, and 12% died from the disease (2 cases of pure DM and 5 cases of combined DM). Although a better prognosis has been postulated for DM when compared with conventional cutaneous malignant melanomas of the same thickness, in most cases, a DM is diagnosed only in established long-standing and thick melanomas. Therefore, dermatologists and dermatopathologists should be more aware of this clinicopathologic variant of cutaneous malignant melanoma.

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Available from: Luís Soares-de-Almeida, Jun 21, 2015
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    • "Desmoplastic melanoma represents a minority (4%) of cutaneous melanomas.5,6 However, a recent study has shown that it is highly represented in malpractice claims related to melanoma.9 "
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    ABSTRACT: Desmoplastic melanoma tends to present as firm, amelanotic papules. Microscopically, it reveals a proliferation of fusiform cells in the dermis and variable collagen deposition, as well as intraepidermal melanocytic proliferation of lentiginous type in most cases. Biopsy in a 61-year-old white male patient, who had received a diagnosis of lentigo maligna on his face 10 years before, revealed a proliferation of dermal pigmented spindle cells and collagen deposition, reaching the deep reticular dermis, with a lentiginous component. Immunohistochemistry with S-100, Melan-A and WT1 showed positivity, but it was weak with HMB45. Desmoplastic melanoma associated with lentigo maligna was diagnosed. Several authors discuss whether desmoplastic melanoma represents a progression from the lentiginous component or arises "de novo". Desmoplastic melanoma represents a minority of cases of primary cutaneous melanoma (less than 4%). Identification of lentigo maligna indicates that desmoplastic melanoma should be carefully investigated.
    Anais brasileiros de dermatologia 06/2013; 88(3). DOI:10.1590/abd1806-4841.20131817 · 0.72 Impact Factor
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    • "The desmoplastic and neurotropic MM patterns often occur together in the same neoplasm [61–63]. The neurotropic features of the neoplasm are regarded as a crucial clue to the diagnosis of desmoplastic MM. "
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    ABSTRACT: During malignant melanoma (MM) progression including incipient metastasis, neoplastic cells follow some specific migration paths inside the skin. In particular, they progress along the dermoepidermal basement membrane, the hair follicles, the sweat gland apparatus, nerves, and the near perivascular space. These features evoke the thigmotropism phenomenon defined as a contact-sensing growth of cells. This process is likely connected to modulation in cell tensegrity (control of the cell shape). These specifically located paucicellular aggregates of MM cells do not appear to be involved in the tumorigenic growth phase, but rather they participate in the so-called "accretive" growth model. These MM cell collections are often part of the primary neoplasm, but they may, however, correspond to MM micrometastases and predict further local overt metastasis spread.
    Dermatology Research and Practice 01/2012; 2012(24):362784. DOI:10.1155/2012/362784
    • "In most cases, a DM is diagnosed only in established long-standing and thick melanomas. Therefore, dermatologists and dermatopathologists should be more aware of this clinicopathologic variant of cutaneous malignant melanoma, de Almeida et al., 2008.[15] Accordingly, this case was reported to increase familiarity of treating physicians with this misleading and disastrous malignancy presenting in an innocent manner; and to introduce a simple technique to close the “difficult-to-close” excisional defects that can be used by surgeons of all specialties and capacities. "
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    ABSTRACT: An elderly female patient was referred to the author for the treatment of a large recurrent pyogenic granuloma in the sole of right foot for a period of 2 years. She underwent excisional surgeries at an outside facility twice in the past. This time, she was treated with wide excision biopsy and the surgical defect was closed with a new technique, the "adjustable suture technique". Histopathology report confirmed "desmoplastic melanoma" with complete marginal clearance. The wound had healed uneventfully. There were no recurrences at 4-year follow-up.
    Indian Journal of Dermatology 04/2010; 55(3):284-9. DOI:10.4103/0019-5154.70706
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