Page 883 - Robbins Basic Pathology by Vinay Kumar, Abul K. Abbas, Jon C. Aster

Benign and Premalignant Tumors 869
AB

CD

Figure 23–22 Melanoma. A, On clinical evaluation, lesions tend to be larger than nevi, with irregular contours and pigmentation. Macular areas
indicate early superficial (radial) growth, while elevated areas often indicate dermal invasion (vertical growth). B, Radial growth phase, with spread of
nested and single-cell melanoma cells within the epidermis. C, Vertical growth phase, with nodular aggregates of infiltrating tumor cells within the
dermis (epidermis is on the right). D, Melanoma cells have hyperchromatic nuclei of irregular size and shape with prominent nucleoli. Mitoses, including
atypical forms such as seen in the center of this field, often are encountered. The inset shows a sentinel lymph node containing a tiny cluster of meta-
static melanoma cells (arrow), detected by staining for the melanocytic marker HMB-45.

melanoma have been seen, especially to antibodies that • In most cases, melanoma progresses from an intraepithe-
block endogenous inhibitors of immune responses such as lial (in situ) to an invasive (dermal) form. Characteristics
CTLA-4 and PD-1, and thus “release the brakes” on host of the dermal tumor such as depth of invasion and mitotic
antitumor immunity. activity correlate with survival.

S U M M A RY BIBLIOGRAPHY

Melanocytic Lesions, Benign and Malignant Curtin JA, Fridlyand J, Kageshita T, et al: Distinct sets of genetic altera-
tions in melanoma. N Engl J Med 353:2135, 2005. [A modified classi-
• Most melanocytic nevi have activating mutations in BRAF or fication of melanoma based on both clinical and genetic features. Such
less often NRAS, but the vast majority never undergo molecular classification schemes are critical for progress in targeted
malignant transformation. therapy.]

• Most sporadic dysplastic nevi are best regarded as markers Elder DE: Dysplastic nevi: an update. Histopathology 56:112, 2010.
of melanoma risk rather than premalignant lesions. They [Balanced presentation of the histology and pathogenesis of dysplastic nevi
are characterized by architectural and cytologic atypia. and their relationship to melanoma.]

• Melanoma is a highly aggressive malignancy; tumors only a Epstein EH: Basal cell carcinomas: attack of the hedgehog. Nat Rev
few millimeters in thickness can give rise to deadly Cancer 8:743, 2008. [Epidemiology, clinical presentation, molecular
metastases. pathogenesis, and novel treatment options are succinctly reviewed.]