Table 1 Clinical, morphologic and immunohistochemical features of MCPyV-negative (n = 21) and -positive MCC (n = 80) cases. Characteristics of the two subsets were compared by non-parametric Mann Whitney and Fisher’s exact tests for quantitative and qualitative data, respectively. For survival analyses, log rank test was used. Positive likelihood ratios for MCPyV positivity were assessed for markers that differed between the two groups (p < 0.05), by MCPyV status, by real-time PCR as the gold standard and predetermined cutoffs (underlined criteria vs rest) [4, 6, 11]

Clinical features

Age, years

0.25

–

  Median, quartiles

81 (76–85)

78 (69–84)

  Missing data

3

4

Sex

0.8

–

  F/M

12/8

45/35

  Missing data

1

0

Immunosuppressive status

0.67

–

  Yes

1 (7%)

9 (16%)

  No

13 (93%)

46 (84%)

  Missing data

7

25

AJCC stage

0.45

–

  I

7 (47%)

18 (27%)

  II

3 (20%)

22 (32%)

  III

5 (33%)

24 (36%)

  IV

0

2 (3%)

  Missing data

6

14

Location

0.09

–

  Head

9 (60%)

21 (30%)

  Trunk

0

4 (6%)

  Upper limb

0

5 (7%)

  Lower limb

5 (33%)

28 (39%)

  Unknown primary

1 (6.7%)

13 (18%)

  Missing data

6

9

Recurrence free, month

0.005

–

  Mean survival, 95% CI

11 (9–13)

66 (54–79)

  Missing data

8

13

Specific death, month

0.027

–

  Mean survival, 95% CI

30 (5–21)

88 (76–99)

  Missing data

8

13

Morphologic features

Nuclear shape

0.005

1.39

  Regular

14 (67%)

74 (93%)

(1.02–1.89)

  Elongated

7 (33%)

6 (7%)

  Uninterpretable cases

0

0

Nucleoli

0.002

1.30

  None/inconspicuous

16 (76%)

78 (99%)

(1.02–1.65)

  Present

5 (24%)

1 (1%)

  Uninterpretable cases

0

1

Cell size

0.026

1.20

  Small (<2 Lc)

5 (24%)

17 (22%)

(0.97–1.49)

  Moderate (2–3 Lc)

12 (57%)

58 (75%)

  Large (>3 Lc)

4 (19%)

2 (3%)

  Uninterpretable cases

0

3

Cytoplasm volume

4×10 ^–7

2.70

  None/inconspicious

7 (33%)

71 (90%)

(1.47–4.96)

  Abundant

14 (67%)

8 (10%)

  Uninterpretable cases

0

1

Clear cytoplasm

2×10 ^-6

1.73

  No

12 (57%)

78 (99%)

(1.19–2.50)

  Yes

9 (43%)

1 (1%)

  Uninterpretable cases

0

1

Rosette-like structure

0.02

1.35

  No

14 (67%)

71 (90%)

(0.99–1.84)

  Yes

7 (33%)

8 (10%)

  Uninterpretable cases

0

1

Intraepidermal component

0.04

1.1

  No

19 (90%)

80 (100%)

(0.96–1.27)

  Yes

2 (10%)

0

  Uninterpretable cases

0

0

Divergent differentiation

0.001

1.24

  No

17 (81%)

80 (100%)

(1–1.52)

  Yes

4 (19%)

0

  Uninterpretable cases

0

0

Associated intraepithelial neoplasia

0.04

1.1 (0.96–1.27)

  No

19 (90%)

80 (100%)

  Yes

2 (10%)

0

  Uninterpretable cases

0

0

Immunohistochemical profile

Cytokeratin 20

0.02

4.5

  Negative

2 (10%)

6 (8%)

(0.64–31.63)

  Diffuse

2 (10%)

0

  Mixed

14 (75%)

52 (68%)

  Dot-like pattern

1 (5%)

18 (23%)

  Uninterpretable cases

2

4

Cytokeratin 8

0.02

1.73

  Negative

0

0

(0.90–3.33)

  Diffuse

0

0

  Mixed

10 (63%)

26 (35%)

  Dot-like pattern

6 (37%)

48 (65%)

  Uninterpretable cases

5

6

Cytokeratin 18

0.006

2.18

  Negative

1 (5%)

0

(1.01–4.70)

  Diffuse

0

0

  Mixed

13 (69%)

28 (39%)

  Dot-like pattern

5 (26%)

43 (61%)

  Uninterpretable cases

2

9

TTF-1

4×10 ^–6

1.92

  Negative

10 (40%)

72 (96%)

(1.24–2.98)

  Positive

10 (50%)

3 (4%)

  Uninterpretable cases

1

5

ATOH1

0.05

–

  Negative

0

1 (1%)

  Low/heterogenous

3 (15%)

29 (38%)

  High and diffuse

17 (85%)

46 (61%)

  Uninterpretable cases

1

4

Neurofilament

0.04

1.49

  Negative

9 (47%)

17 (22%)

(0.95–2.31))

  Dot-like pattern

10 (53%)

61 (78%)

  Uninterpretable cases

2

2

SATB2

0.07

–

  Negative

5 (25%)

6 (8%)

  Low/heterogenous

6 (30%)

19 (24%)

  High and diffuse

9 (45%)

54 (68%)

  Uninterpretable cases

1

1

CD99

0.02

8.08

  Negative

1 (5%)

12 (15%)

(2.16–30.21)

  Dot-like pattern

2 (10%)

63 (81%)

  Diffus

17 (85%)

3 (4%)

  Uninterpretable cases

1

2

PAX5

0.90

–

  Negative

16 (80%)

57 (74%)

  Low/heterogenous

4 (20%)

16 (21%)

  High and diffuse

0

4 (5%)

  Uninterpretable cases

1

3

TdT

0.34

–

  Negative

16 (89%)

60 (76%)

  Positive

2 (11%)

19 (23%)

  Uninterpretable cases

3

1

EMA

0.003

2.70

  Negative

5 (25%)

22 (29%)

(1.10–6.64)

  Low/heterogenous

11 (55%)

13 (17%)

  High and diffuse

4 (20%)

41 (54%)

  Uninterpretable cases

1

4

Cytokeratin 7

0.006

1.36

  Negative

12 (71%)

69 (96%)

(1–1.85)

  Positive

5 (29%)

3 (4%)

  Uninterpretable cases

4

8

p53

2×10 ⁻⁹

3.63

  No expression

7 (37%)

2 (3%)

(1.71–7.7118)

  Heterogenous expression

5 (26%)

63 (95%)

  Overexpression

7 (37%)

1 (2%)

  Uninterpretable cases

2

14

Large T antigen

2×10 ⁻⁹

–

  Negative

17 (100%)

17 (23%)

  Positive

0

58 (77%)

  Uninterpretable cases

4

5