Micronodular thymic tumor with lymphoid stroma: A case report and review of the literature

Table 1 Summary of the immunohistochemistry results in our case

	Tumor cells	Lymphocytes in stroma
CD5	Diffuse, strong, cytomembrane	Focal, strong, cytomembrane
CD3	Negative	Focal, strong, cytomembrane and cytoplasm
CD20	Negative	Focal, strong, cytomembrane
CD117	Diffuse, strong, cytomembrane and cytoplasm	Negative
CK-pan	Diffuse, strong, cytoplasm	Negative
CK-19	Diffuse, strong, cytoplasm	Negative
Bcl-2	Focal, strong, cytomembrane and cytoplasm	Focal, strong, cytomembrane and cytoplasm
Her-2	Negative	Negative
P53	Mottled expression	Negative
Ki-67	Approximately 30% of cells, strong, nucleus	Focal, especially in the germinal center, strong, nucleus
TdT	Negative	Negative

Table 2 Summary of cases in the literature

Variable item	Number of cases	Percentage (%)
Age (median, age span)	63, 41-83	-
Sex
Male	51	53.7
Female	44	46.3
Benignity and malignancy[2,27]
Benign (MNT)	77	81.1
Malignancy (MNC)	18	18.9
Site
Thymic source	92	96.8
Extra-thymic source	3	3.2
Clinical symptoms
No obvious symptoms	76	80.0
Local symptoms	11	11.6
Immune related symptoms	8	8.4
Masaoka stage
1	52	59.8
2a	16	18.4
2b	13	14.9
3	4	4.6
4	2	2.3
Tumor size (cm) (mean, standard deviation, size span)	5.14 ± 2.32, 1.2-10	-
Tumor cross section
Cystic or cystic and solid	35	44.3
Solid	44	55.7
Tumor cell atypia
No	58	66.7
Mild	6	6.9
Moderate	7	8.0
Severe	16	18.4
Mitotic figures[25]
≤ 2/10 HPF	62	78.5
2/10 HPF	17	21.5
Necrosis
No	38	77.6
Yes	11	22.4
CD5 staining in tumor cells
Negative	43	79.6
Focally positive or diffusely positive	11	20.4
Ki-67 staining[25]
≤ 2% of tumor cells	15	51.7
2% to 10% of tumor cells	5	17.2
≥ 10% of tumor cells	9	31.0
TdT positive lymphocytes
No	12	42.9
Few	7	25.0
Many	9	32.1
Treatment
Resection	84	93.3
Resection + radiotherapy or chemotherapy	4	4.4
Radiotherapy + chemotherapy	1	1.1
No treatment	1	1.1
Follow-up time	2 d to 22 yr
Follow-up results
Loss to follow-up	18	21.2
No relapse or metastasis	60	70.6
Tumor relapse	1	1.2
Death caused by nontumorous reason	5	5.8
Tumor-caused death	1	1.2

HPF: High power fields.

Table 3 Characteristics of micronodular thymoma with lymphoid stroma and micronodular thymic carcinoma with lymphoid hyperplasia

	MNT group	MNC group	t or χ2	P
Age	63.4 ± 9.45	63.4 ± 9.45	1.954	0.054
Sex			0.31	0.860
Male	41	10
Female	36	8
Clinical symptoms			0.577	0.749
No	65	14
Local symptoms	8	3
Immune related symptoms	4	1
Masaoka stage			18.980	< 0.001
I	44	8		< 0.001
II	26	3
III	1	3
IV	0	2
Mitotic figures			41.214	< 0.001
≤ 2/10HPF	61	1
> 2/10HPF	6	11
Cell atypia			75.792	< 0.001
No	57	1
Mild	6	0
Moderate	6	1
Severe	0	16
Tumor size	43.34 ± 43.094	53.00 ± 73.04	0.539	0.591
Tumor necrosis			12.459	< 0.001
No	31	7
Yes	0	4
Follow-up results
No relapse or metastasis	51	9	9.582	0.002
Tumor relapse or tumor-caused death	0	2
CD5 staining in tumor cells			5.264	0.022
Negative	44	12
Positive	1	4
Ki67 staining in tumor cells			13.426	0.001
≤ 2%	15	0
2-10%	5	0
≥ 10%	4	5
TdT positive lymphocytes			14.933	000
No	4	8
Yes	16	0
Treatment			9.697	0.021
Resection	71	13
Resection + radiotherapy or chemotherapy	3	1
Radiotherapy + chemotherapy	0	1
No treatment	0	1

MNT: Micronodular thymoma with lymphoid stroma; MNC: Micronodular thymic carcinoma with lymphoid hyperplasia; HPF: High power fields.