lentigo maligna

Introduction

Macular intra-epidermal neoplasm. Precursor of lentigo maligna melanoma.

Epidemiology

• most common in elderly
• lifetime risk:
  • 4.7% 45 years of age
  • 2.2% 65 years of age

Pathology

• early lesions confined to epidermis
• thickening & invasion of underlying tissue indicates progression to lentigo maligna melanoma
• insult to DNA of basilar layer melanocytes in sun-exposed skin
• prolonged radial growth phase may precede progression to lentigo maligna melanoma
• atypical cells are not distributing uniformly throught the lesion

Clinical manifestations

• begins as uniformly pigmented light brown macule
  • evolves to pigmented macular lesions with variation in hues of brown & black
• focal papular & nodular areas indicate invasion into the dermis & progression to lentigo maligna melanoma
• 3 mm to 2 cm or larger in size
• distribution:
  • single isolated lesion on sun-exposed surface (head & neck)
• shape: irregular but sharply defined borders with inlets & peninsulas
• enlarges gradually, over a period of years
• other manifestations of sun-damaged skin
  • telangiectasia
  • marked freckling
  • atrophy & solar keratosis
  • basal cell carcinoma

Laboratory

• shave biopsy
  • exception to do not shave a pigmented lesion

Differential diagnosis

• lentigo maligna melanoma
• solar lentigo

Management

• check for regional lymphadenopathy
• surgical excision
  • margin of at least 1.0 cm beyond clinically visible lesion
  • use of Wood's lamp may help define borders
  • excision down to or including the fascia
  • skin graft will be necessary
  • dissection of regional lymph node only if clinically palpable
  • neoadjuvant topical imiquimod, 5%, cream prior to conservatively staged excision may allow for negative histologic margins of 2 mm

More general terms

• lentigo; melanocytic macule

Additional terms

• lentigo maligna melanoma
• solar (senile) lentigo