Lentigo maligna melanoma

Skin melanocytic tumor
Melanoma
Lentigo maligna melanoma

Topic Completed: 1 May 2013

Revised: 28 May 2019

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Table of Contents

Cite this page: Hale CS. Lentigo maligna melanoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skintumormelanocyticlentigomaligna.html. Accessed December 7th, 2019.

Definition / general

Atypical melanocytes in basal layer, individually and in nests (theques), associated with sun damage (eMedicine)

Terminology

Also called melanoma arising in Hutchinson freckle, actinic melanosis, melanoma on sun damaged skin and solar melanoma
Note: lentigo maligna (a subtype of melanoma in situ), by definition, does NOT infiltrate into dermis but lentigo maligna melanoma has at least single cell infiltration into papillary dermis

Clinical features

Flat, tan to black with irregular hyperpigmentation, > 2 cm
5 - 15% of (invasive) melanoma; increasing prevalence, particularly among men age 65+ years (J Invest Dermatol 2005;125:685)
Slow growing lesion of sun exposed skin of elderly whites, often cheek; partial regression is common
Similar behavior to other melanoma subtypes when depth of invasion is considered but unusual to die of disease
Possible origin from progenitor stem cell (strongly CD133+ and CD34+) in outer root sheath of mid lower hair follicles (Dermatol Ther 2008;21:S1)

Case reports

51 year old woman with Fitzpatrick skin type III (Dermatology 2008;217:66)
Collision tumors: 79 year old man with coexisting Merkel cell carcinoma (J Cutan Pathol 2008;35:203), 82 year old woman with coexisting basal cell carcinoma (Am J Dermatopathol 2005;27:319), with coexisting gastrointestinal stromal tumor (Am J Clin Dermatol 2012;13:64)

Treatment

Excision with careful margin control (J Am Acad Dermatol 2008;58:142)
Staged excision for peripheral margin control using permanent sections is required because frozen sections are unreliable (Plast Reconstr Surg 2007;120:1249)
Possibly radiation (Surg Clin North Am 2003;83:323)
Possibly imiquimod without (Ann Plast Surg 2008;61:419) or with surgery (Dermatol Surg 2008;34:147)
Possibly cryotherapy

Dermoscopy

Annular granular pattern (Br J Dermatol 2012;167:280), asymmetric pigmented follicular openings, dark rhomboidal structures and homogeneous areas

Dermoscopy Images

Images hosted on other servers:

Annular granular pattern

With slate gray dots

Typical dermoscopy features

Clinical images

Images hosted on other servers:

Various Images

Microscopic (histologic) description

Contiguous growth of atypical melanocytes in basal layer, individually and in nests (theques)
Cells may be spindled, pleomorphic and have cytoplasmic retraction
Dermis shows solar elastosis
Also epidermal atrophy, actinic damage and basilar keratinocyte hyperpigmentation

Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Angel Fernandez-Flores, M.D., Ph.D.

Various images

Images hosted on other servers:

Atypical melanocytes

Molecular / cytogenetics description

p.R163Q variant of MC1R gene is associated with lentigo maligna melanoma in Mediterranean populations (Br J Dermatol 2013;169:804)

Differential diagnosis

Desmoplastic melanoma: may arise secondary to lentigo maligna
Lentiginous nevi
Lentigo maligna in situ melanoma