Case 28 Male, 55 years. Skin tumour, backShow diagnosis & comments
Desmoplastic melanoma with neurotropism
- Usually arises in chronically sun-damaged skin
- Nondescript papule, plaque or more diffuse induration and thickening of the skin
- Punch biopsy diagnosis requires a high level of suspicion (S-100 immune stain is mandatory and usually clinches the diagnosis).
- Nonpigmented proliferation of elongated atypical cells within the dermis, associated with newly formed collagen
- Mitotic figures usually uncommon
- Enlarged hyperchromatic elongated nuclei, often with coarse chromatin and plump nucleoli
- No melanin pigment
- Cells lie singly or in small elongated cell groups
- S-100 stain strongly positive, most other melanocyte markers such as Melan-A and HMB-45 negative.
- Perivascular round cell inflammatory infiltrates
- There may or may not be an intraepithelial atypical melanocytic proliferation
- Peri- or intraneural growth resulting in increased likelihood of local recurrence (NEUROTROPIC MELANOMA')
- Metastasis is rare in pure demoplastic melanomas; not rare when the melanoma also shows a non-desmoplastic component
- Busam KJ. Cutaneous desmoplastic melanoma. Adv Anat Pathol. 2005;12(2):92-102.
- Busam KJ, Mujumdar U, Hummer AJ, Nobrega J, Hawkins WG, Coit DG, Brady MS. Cutaneous desmoplastic melanoma: reappraisal of morphologic heterogeneity and prognostic factors. Am J Surg Pathol. 2004;28(11):1518-25.
- Magro CM, Crowson AN, Mihm MC. Unusual variants of malignant melanoma. Mod Pathol. 2006 Feb;19 Suppl 2:S41-70.