By Gary M. White, MD
Desmoplastic melanoma (DM) represents about 4% of melanomas. Since it often does not appear like a classic melanoma, delay in diagnosis and a poorer prognosis is a concern.
A deep dermal or subcutaneous nodule best appreciated by palpation and usually not pigmented is characteristic. The mean age of onset is approximately 60 years, and the majority of patients are men. The most common location is the head and neck, especially underlying a lentigo malignant melanoma but it may also occur as a feature of acral lentiginous melanoma. It may affect other parts of the body, including the mucosa. Due to the difficulty in diagnosis, both clinically and histologically, adequate treatment is often delayed and prognosis is often poor. There is a high recurrence rate and a propensity for metastasis. In one series, the suspected diagnosis varied widely from BCC, lentigo, verruca, Spitz nevus, pyogenic granuloma, lentigo maligna, sebaceous cyst, nodular melanoma, granuloma faciale and pilomatricoma.
Some tumors present with a pure desmoplastic invasive component (>90%) while other tumors display mixed features of DM and nondesmoplastic melanoma. This is important as pure desmoplastic melanomas (desmoplasia throughout the tumor) have less regional metastasis given the same Breslow's depth as conventional melanoma [JAAD 2013: 68:825-833].
Many experts believe that the risk of developing nodal involvement in DM is lower than for patients with nondesmoplastic melanoma. In addition, the prognostic value of a SLN may not be the same for DM as for classic melanoma. Thus, some authors are now recommending against routine SLN biopsy in the case of DM. Hopefully, more studies in the future will clarify recommendations in this area.
Wide local excision with a 2 cm margin, if possible, is recommended. If a 2 cm margin is not possible, adjuvant radiation therapy may be considered. See also melanoma.
Desmoplastic melanoma associated with an intraepidermal lentiginous lesion: case report and literature review An. Bras. Dermatol. vol.88 no.3 Rio de Janeiro May/June 2013
Dermatology Research and Practice Volume 2009
Subungual desmolplastic melanoma JEADV 2016;30;360
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