Desmoplastic melanoma: a review

Abstract

Desmoplastic melanoma (DM) is a variant of spindle cell melanoma typically found on chronically sun-damaged skin of older individuals. Early diagnosis can be challenging because it is often amelanotic and has a predominantly dermal component. DM can be difficult to diagnose not only clinically but also histologically, and can be mistaken for a variety of benign and malignant nonmelanocytic spindle cell tumors when viewed on prepared histopathology slides. Pathologists have observed that DMs can manifest significant variation with respect to the extent of intratumoral cellularity, fibrosis, and/or perineural invasion. Furthermore, some tumors present with a pure desmoplastic invasive component (>90%) while other tumors display mixed features of DM and nondesmoplastic melanoma. This has led to the separation of DM into 2 histologic subtypes, pure and mixed. With a focus on the distinction between pure and mixed DM, this review will detail what is currently known about the diagnostic features of DM, discuss risk and prognostic factors, and examine the current literature on disease progression and management.

Figure 1

Clinical and dermoscopic features of desmoplastic melanoma, pure type. (A) overview (B) close-up shows a firm cystic to scar-like nodule on the chest of 67 year-old male with a history of multiple primary melanomas. Biopsy revealed a 6.1mm DM, pure subtype, Clark's level V, Mitotic index 1, with perineural invasion. (C) Under dermoscopy, atypical dotted vessels were observed (arrow)

Figure 2

Clinical and dermoscopic features of desmoplastic melanoma, mixed type. (A) overview (B) close-up shows an erythematous plaque on the mid-back of 71 year old male (arrow). This proved to be a 0.95mm superficial spreading melanoma with focal invasive desmoplastic melanoma, mixed subtype. (C) Under dermoscopy, regression structures, vascular blush and polymorphous vessels were observed.

Figure 3

Desmoplastic melanoma, pure type (H&E). A: Amelanotic spindle cell melanoma is associated with collagenous stroma and lymphocytic aggregates. B: Individual hyperchromatic fusiform melanocytes are dispersed in a fibrous matrix.

Figure 4

Desmoplastic melanoma, mixed type (H&E). A: One part of the invasive melanoma displays a fibrosing spindle cell component. B: Another part of the melanoma is composed of densely cellular aggregates of epithelioid tumor cells.