Merkel cell carcinoma: Diagnosis, staging, sentinel lymph ... · lymph node biopsy and prognostic markers . Michael T. Tetzlaff MD, PhD . Associate Professor . Department of Pathology

Merkel cell carcinoma: Diagnosis, staging, sentinel

lymph node biopsy and prognostic markers

Michael T. Tetzlaff MD, PhD

Associate Professor Department of Pathology (Dermatopathology)

Department of Translational and Molecular Pathology

The University of Texas MD Anderson Cancer Center

Executive Officer

Translational Research Program The Alliance for Clinical Trials

Update on Merkel cell carcinoma

Merkel cell carcinoma

Diagnosis and

molecular pathogenesis

New therapeutics and implications for

pathologists

Staging Sentinel lymph node Prognostic markers

Merkel cell carcinoma

• Described 5 cases of “trabecular carcinoma” of the skin • Tumors consisted of ‘irregular, angular, anastomosing

trabeculae’ infiltrating among dermal collagen as cords • Cells with oval, vesicular nuclei and indiscernible

cytoplasm

CK20

CHG SYN

Cam5.2 TTF1

LCA

Immunohistochemical studies inform the diagnosis of Merkel cell carcinoma

Differential diagnosis of Merkel cell carcinoma

Diagnosis Morphology IHC BCC • Peripheral palisading

• Clefting • MCPy-T-antigen negative • Lacks prominent CK20+

Melanoma • Pigmented • Prominent

intraepidermal

• S100+, MART-1+, Sox-10+, HMB-45+

• Cytokeratin- Lymphoma/Leukemia • Dishesive • Positive for lymphoid markers

• Negative for cytokeratins Sebaceous carcinoma

• Lacks neuroendocrine chromatin

• CK7+ • CK20- and MCPy-T antigen

negative Metastatic neuroendorcine carcinoma

• Overlapping • TTF-1+ • CK7+ • CDX-2+ • MCPy-T-antigen negative

Immunohistochemical studies inform the diagnosis of Merkel cell carcinoma

Combination of TTF1- and CK20+

TTF-1 and CK20 in the diagnosis of Merkel cell carcinoma

CK20

TTF1

Spectrum of lesions with variable positivity for TTF1 and/or CK20. Diagnosis based on clinical and where the lesion falls on that spectrum.

CK20

TTF1

Demographics of Merkel cell carcinoma • MCC is the most aggressive form of skin cancer

• ~35% of patients with nodal disease at presentation • ~10% of patients with systemic metastases at presentation • Estimated mortality rate: 33%-46%

• Risk factors for MCC are age and immunosuppression

• Elderly • Accumulation of mutations from ultraviolet light

• Organ transplantation, HIV+, CLL • Merkel cell polyomavirus (MCPyV)

• MCC affects older Caucasian men and is most commonly on the head and neck

• 70% of patients are >70 years old • 62% of patients are male • 43% of patients head and neck

Merkel cell carcinoma driven by polyomavirus infection

In comparison to MCPyV-positive MCCs (n=12): • MCPyV-negative MCCs (n=19)

• Arise on chronic uv-exposed sites • Exhibit a much higher mutational burden

Mutational signature of Merkel cell carcinoma depends on MCPyV

In comparison to MCPyV-positive MCCs (n=7): • MCPyV-negative MCCs (n=8)

• A significantly higher mutational burden • A UV-type mutational signature

Mutational signature of Merkel cell carcinoma depends on MCPyV

Mechanisms of Merkel cell carcinomagenesis Common pathways abrogated by distinct mechanisms: mutation or virus

Viral inactivation of RB and

TP53 related pathways

Mutational inactivation of TP53 and

RB

MCPyV+ MCC

MCPyT

MCPyV- MCC

MCPyT

PRC2 Silences gene regions by methylation (H3K27me)

αMCPyVT

αH3K27me

Viral inactivation of RB and

TP53 related pathways

Mutational inactivation of TP53 and

RB

MCPyV+ MCC

MCPyT

MCPyV- MCC

MCPyT

Mechanisms of Merkel cell carcinomagenesis Common pathways abrogated by distinct mechanisms: epigenetic or virus

Staging Merkel cell carcinoma Cases with follow-up and complete staging

n=9,387

• Survival directly correlates with overall disease burden • Local disease > Nodal metastases > Distant metastases • Tumor size (and thickness) is a critically important prognostic indicator

Histopathologic features of Merkel cell carcinoma that correlate with outcome: What do we report and why?

Retrospective review of 156 patients with MCC with median follow up 51 months (range: 3-224 months)

• Among patients with lymph node negative early stage MCC (Stage I and II)

• Pattern of growth (Nodular versus infiltrative) • Deepest anatomic compartment of involvement • Tumor thickness (< vs ≥ 5 mm) • Lymphovascular invasion • Tumor infiltrating lymphocytes (absent vs present)

Histopathologic features of Merkel cell carcinoma that correlate with outcome: What do we report and why?

Clinical staging system for Merkel cell carcinoma Based on pathologic staging of primary and clinical evidence of metastases

T-

cN-

cM-

Pathologic staging system for Merkel cell carcinoma Based on pathologic staging of primary and metastatic disease

T-

pN-

pM-

Metastasis in MCC is relatively common and is an important predictor of survival: The sentinel node

Pan-Cytokeratin cocktail

• Approximately 50% of patients with MCC present with metastases

• 35% with nodal disease • 15% with distant metastases

• Among patients with negative lymph node following examination of initial H&E

• An additional 40% of patients with lymph node metastases are identified by examining additional tissue levels and immunohistochemical studies with pan-CK or CK20

Value of immunohistochemical studies in assessing sentinel lymph nodes for MCC

10 patients 23 SLNBs

All negative on 1st H&E

5/23 SLN+ (21.7%)

4/10 patients (40%)

IHC for PanCK

or CK20








• Lymph node status correlates with outcome • Clinically node positive disease fares worst • Pathological node negative disease fares best

SLN is an important prognostic tool for patients with MCC

59%

26%

76%

42%

Metastasis to the SLN in MCC is an important predictor of distant relapse and survival (in most studies)

721 patients 736 SLNBs

218 SLN+ (29.6%)

518 SLN- (70.4%)

• Regional nodal relapse not significantly different between SLNB+ (11.2%) and SLNB- (8.7%) patients

• Distant relapse far more frequent among SLNB+ (17.6%) compared to SLNB- (7.3%) patients (p<0.001).

• Sentinel lymph node status is a robust indicator of distant relapse and overall survival in MCC.

Pattern of sentinel lymph node positivity correlates with survival in Merkel cell carcinoma

Pattern 1 Pattern 2

Pattern 3 Pattern 4

Pattern 5

• Among patients with lymph node involvement by MCC (H&E or IHC)

• What are the patterns of involvement? • Do these patterns correlate with

clinical outcome? • What is the significance of metastatic

MCC determined only by IHC?

Pattern of involvement


Pattern 1 Pattern 2

Pattern 3 Pattern 4

Pattern 5

Number of nodes






Pattern 1 Pattern 2

Pattern 3 Pattern 4

Pattern 5

Age






Prognostic factors in Merkel cell carcinoma: p63 CK20 CHG SYN p63

• n= 47 pts with MCC • 25 p63+ • 22 p63-

p63-positive MCCs have worse survival than p63-negative MCCs

n= 70 pts with MCC • 43 p63+ • 27 p63-

Assessed for association between survival:

• Age • Gender • Anatomic site • Tumor size • Tumor thickness • Cell size • LVI • Mitotic figures • TILS • Pattern of growth • Stage • p63 • p53 • Ki-67 (MIB1) • MCPyV status

Prognostic factors in Merkel cell carcinoma: p63

Stage I-II MCC

Not all studies support the prognostic significance of p63

• n= 26 pts with MCC • 20 p63+ • 6 p63- NO ASSSOCIATION

• n= 128 pts with MCC • 42 p63+ • 86 p63-

All patients Stage I Stage II

Stage III Stage IV

No significant correlation

within a given stage

Prognostic factors in Merkel cell carcinoma: p63 ?

Prognostic factors in Merkel cell carcinoma: Status of the immune system

• Advanced patient age and male sex associate with worse prognosis(Laryngoscope. 2012. 122:1283-90.)

• Immunosuppression is a risk factor for developing MCC and correlates with worse outcome independent of stage.

• n= 471 pts with MCC • n= 430 immunocompetent • n= 41 immunosuppressed

• n=21 CLL/hematologic malignancy

• n=5 HIV/AIDS • n=15 iatrogenic

• transplant • autoimmune

Composition and density of the immune system is prognostic Merkel cell carcinoma

• n=62 MCCs • IHC CD3, CD8, PD-1, and PD-L1 • Quantified with Aperio

automated image analysis

Composition, density and distribution of the immune infiltrate is prognostic Merkel cell carcinoma

Does the composition, density and/or distribution of the associated immune infiltrate associate with survival in MCC?

CD3 IHC CD3 IHC-quantified/mm2

Density of the CD8+ T-cell infiltrate at the tumor periphery associates with survival Effect appears to be amplified in MCPyV+ compared to MCPyV- MCCs

Composition, density and distribution of the immune infiltrate is prognostic Merkel cell carcinoma

Leveraging the immune system to combat MCC

• Immunity and Merkel cell carcinoma • Immunosuppression

• Risk factor for the development of MCC • Correlates with worse prognosis independent of stage

• Immune infiltrates correlate with prognosis • Increasing CD8+ T-cells at tumor periphery associates with improved survival

• Robust frequency of neoantigens in MCC (MCPyV or high mutational burden)

• Immunity and Merkel cell carcinoma • Immunosuppression

• Risk factor for the development of MCC • Correlates with worse prognosis independent of stage

• Immune infiltrates correlate with prognosis • Increasing CD8+ T-cells at tumor periphery associates with improved survival

• Robust frequency of neoantigens in MCC (MCPyV or high mutational burden)

Leveraging the immune system to combat MCC

Response to anti-PD-1 in Merkel cell carcinoma

• 56% objective response rate to PD-1 inhibitor among stage IIIb or IV MCC patients who had not received prior systemic therapy—independent of MCPyV status or the relative

expression of PD-L1.

32% (28/88) patients with stage IV MCC who failed at least one prior systemic therapy achieved

rapid and sustained response to PD-L1

inhibitor—independent of

MCPyV status or the relative expression of

PD-L1.

Response to anti-PD-L1 in Merkel cell carcinoma

FDA approval for MCC

Merkel cell carcinoma • MCC is the most aggressive form of skin cancer

• Risk factors are age, exposure and immunosuppression

• MCC responds to immune checkpoint blockade • Thus far, independent of PD-L1 or MCPyV status

• Important parameters of the primary lesion • Size, depth, lymphocytic infiltrate, LVI, pattern of growth • Staging according to TNM criteria

• MCC is related to infection by Merkel cell polyoma virus • Viral T-antigens impact on Rb and TP53-dependent processes • MCPyV-negative MCC enriched for UV-mutations (in particular TP53 and RB)

• Prognostic biomarkers include: • Immune infiltrate • p63 expression by tumor cells, but utility is questionable

Thank you….. Department of Pathology, Section of Dermatopathology, MDACC • Victor G. Prieto MD, PhD • Carlos A. Torres-Cabala MD • Jonathan L Curry MD • Priyadharsini Nagarajan MD, PhD • Phyu Aung MD, PhD • Doina Ivan MD

Laurence Feldmeyer, MD, PhD Courtney W. Hudgens, BS Department of Pathology, Cleveland Clinic • Steven D Billings MD • Jennifer S. Ko MD, PhD

• RB expression lost in MCPyV- MCCs but preserved in MCPyV+ MCCs

Complex relationships between MCPyV and TP53 and RB

• TP53 expression detected (surrogate for TP53 mutation) in MCPyV- MCCs but not in MCPyV+ MCCs.

• Suggest MCPy machinery interferes with RB and TP53-dependent pathways while MCPyV- MCCs rely on mutational inactivation.

Documents

Merkel cell carcinoma: Diagnosis, staging, sentinel lymph ... · lymph node biopsy and prognostic markers . Michael T. Tetzlaff MD, PhD . Associate Professor . Department of Pathology