Application of Immunohistochemistry to the Diagnosis of Melanocytic Lesions PerĂş 2013 Victor G. Prieto, MD, PhD Professor Depts. of Pathology and Dermatology University of Texas MD Anderson Cancer Center Houston TX, USA
Index • Introduction • Immunohistochemistry • Differential diagnosis • New techniques (in the case discussion) • Conclusions
Introduction • Growing incidence of
melanoma • Growing number of biopsies • Gray areas (black / white) • Need for additional techniques
Immunoperoxidase in Dermatopathology
• Multiple applications • Several antibodies
S100 protein
HMB45 Nevus
Melanoma
MART1
Ki67
MITF
SOX10
IPOX in Dermatopathology: Special Situations
• Diagnosis (melanocytic differentiation)
• Depth of invasion • Distinction between benign/ malignant
Detection of Melanocytic Differentiation
• Poorly differentiated lesions • Pan-melanocytic cocktail (HMB45, anti-MART1, MelanA, anti-tyrosinase) • Keratin • SMA • 2nd line: SOX10, S100
MART1
S100 protein
Detection of Level of Invasion
• Questionable dermal invasion
• Desmoplastic melanoma
Keratin
Scar-like, but epidermal hyperplasia
S100
Differentiation between benign and malignant lesions
Blue Nevus Family vs. Melanoma • Mitotic figures • Patchy HMB45 • Necrosis • Increased MIB1 • Cytologic atypia • Biphenotypic pattern (nevus + mel.) • “Atypical” BN: – (Scalp) – Scattered mitotic figures OR – Necrosis OR – Cytologic atypia Tran et l. J Cutan Pathol 1998; 25: 252-258
Large lesion Uniform pigmentation
Elongation of rete ridges, small junctional component
Uniform cells, small nucleoli
Ki67
HMB45, Cellular blue nevus
Irregular pigmentation
Pleomorphism, irregular pigmentation
Nuclear pleomorphism
Cellular blue nevus with atypical features
Ki67/MART1
HMB45
Large nodule, originally called metastatic melanoma
Melanoma arising in a blue nevus
Necrosis, mitotic figures
Pigmented Epithelioid Melanocytoma • a.k.a. animal melanoma (pejorative term) • Epithelioid cells • Cytologic atypia • Relatively benign behavior
Zembowicz, Carney, Mihm. Am J Surg Pathol 2004;28:31-40"
Pigmented Epithelioid Melanocytoma
• Of 24 cases with LNs, 11 met and 1
liver metastasis • Follow-up (mean 32 months, range up to 67 months): No DOD • Ulceration rare; in epithelioid blue nevi of the Carney complex • Protein kinase a regulatory subunit 1α
Marked pigmentation Ulceration
Marked pigmentation Apparently densely cellular
Pigmented epithelioid melanocytoma
Melanocytes Macrophages
Key Points Blue Nevus-Type Lesions • Cellularity • Distribution of pigment • No or very rare mitotic figures • Diffuse expression of HMB45 antigen and MART1 • Low proliferation rate
• PEM Low-grade melanoma?
Spitzoid Lesions
• Current trend to designate these lesions as tumors
• Likely a spectrum between benign and malignant
• Mostly a histologic diagnosis
Spitz Nevus • Originally described as
Juvenile melanoma (Sophie Spitz) • Histologic similarities with melanoma • Mostly children and young adults
Histologic Features – Circumscription
– Maturation
– Symmetrical
– No dermal mitotic figures
– Absent or central pagetoid migration – Uniformly atypical – Vertically oriented cells nests
– Kamino bodies – IPOX
Histologic Features – Circumscription
– Maturation
– Symmetrical
– No dermal mitotic figures
– Absent or central pagetoid migration – Uniformly atypical – Vertically oriented cells nests
– Kamino bodies – IPOX
Wedge shape Papular
Infiltration of adipose tissue
Kamino bodies
Maturation
HMB45
Differential Dx: Spitzoid melanoma • Older patients (but not an exact science!) • Asymmetry • Poorly circumscribed
No junctional component No clear maturation
Vascular invasion
Irregular pigment deposition
HMB45
Metastatic melanoma
HMB45
• Irregular nests • No maturation
• Marked pleomorphism
• Confluent pattern • Atypical mitotic figures
HMB45: top bottom
Spitzoid melanoma
MIB1 (deep)
Key Points Spitzoid Lesions • Age only partially helpful • Symmetrical • Wedge shaped • No or very rare mitotic figures • Maturation (H&E and IPOX)
Desmoplastic Nevus vs. Desmoplastic Melanoma
• Head and neck • Mitotic figures • High expression of Ki67 • Expression of gp100 in the
deep region • Patchy MART1 expression
35 yo W trunk
Dense cellular infiltrate
Called melanoma at another institution
Lymphoid aggregates Focal atypia
55-yo W, shoulder
Dense cellular infiltrate
Junctional component Cellular atypia
HMB45 MART1
S100
Nevus
Melanoma
S100
MART1
Distinction Between Scar and Desmoplastic Melanoma
S100
S100
Lentigo Maligna vs. SunDamaged Skin
• Diffuse, confluent growth of atypical melanocytes in the epidermis
• HMB45 / pan mel cocktail • MiTF1 (nuclear)
MART1 HMB45
MART1 HMB45
MiTF1
Margins of Lentigo Maligna
• Discourage use of frozen sections Prieto et al, AJCP 2003; 120: 203
• “Slow” Mohs (rapid processing in paraffin to allow wound closure)
Unexpected IPOX results
Bleaching Technique • Allows better analysis of morphology in heavily pigmented lesions • Modifies some of the antigens: – HMB45 in macrophages – Melan A in macrophages • Requires standardization in each laboratory
Densely cellular neoplasm
Marked atypia
Partial loss of S100
S100
PanMel
S100 CD68 Outside Dx: Atypical fibroxanthoma
S100
MART1 CTL
S100
MART1
Primary, invasive melanoma
MART1 • Majority of melanocytes (except for
desmoplastic / spindle cell melanoma) • MART1 artefactually positive: – Diffuse labeling of dendrites in sundamaged skin – Macrophages (then use HMB45 or anti-MITF1) Trejo O, Reed JA, Prieto VG. J Cutan Pathol 2002; 29: 397-406 El Shabrawi-Caelen L, Kerl H, Cerroni L. Am J Dermatopathol. 2004;26:364-6 Wiltz KL et al. J Cutan Pathol. 2007;34:601-5
HE
MART1
CD68
HMB45 in Nevi
• Superficial cells (Spitz, blue) • Usually not in nodal nevi • Interlaboratory variation • Traumatized nevi Biddle DA, et al. Intraparenchymal nevus cell aggregates in lymph nodes: a possible diagnostic pitfall with malignant melanoma and carcinoma. Am J Surg Pathol 2003; 27: 673-681
MART1
Outside HMB45
HMB45
Irregular HMB45 in traumatized nevi Adeniran, Prieto, Chon, Duvic, Diwan. JAAD 2009
Final Summary • Melanocytic benign and malignant lesions: Histologic diagnosis
• Correlation with special studies and clinical features
• Expect the unexpected!