Metastatic Malignant Thymoma
Thymomas are epithelial tumors of the thymus accounting for ~25 % of all mediastinal tumors.
They show a cytologically benign epithelial component and tend to remain encapsulated within the
thymus. A cytologically benign thymoma can invade and metastize to other sites and is termed
metastatic malignant thymoma.
Invasive thymomas are relatively rare tumors representing less than 1% of all malignancies. Most
patients with thymoma are aged 40 through 60 years and are asymptomatic at the time of
diagnosis. They may also present with cough, chest pain, superior venacava syndrome, and
dysphagia. Many patients also have myasthenia gravis (MG).
Metastatic malignant thymoma shows the typical biphasic cell pattern of a thymoma. The tumors
are predominantly epithelial, compared with the lymphoid component. In most cases, the epithelial
cells are predominantly of the epithelioid (cortical) cell type. The nuclei may be larger, and the
nucleoli more prominent, than in the epithelial component of ordinary thymoma. The presence of
cytologic atypia and numerous mitotic figures may correlate with more aggressive behavior.
However, invasion, not cellular morphologic characteristics, is the key to the diagnosis, and invasion
cannot be assessed cytologically.
Clinical History/Findings
The patient is a 26 year-old white male with a pleural nodule and a history of thymoma.
Specimen Type
An ultrasound guided fine needle aspiration biopsy (FNAB) and core biopsy of right paraspinal lesion
was performed.
Cytologic Findings
IHC Results:
Cytologic & Surgical Diagnosis:
Metastatic Malignant Thymoma
Commentary: These results are most consistent with metastatic malignant thymoma
as evidenced by the extensive invasion to the lung, thorax, and paraspinal lesions
and the dimorphic pattern of epitheliod and lymphocytic cells. The
immunohistochemical staining is consistent with a thymoma.
Submitted by:
Ann Marie West, BS, CT (ASCP)
Parkland Health & Hospital System
Dallas, Texas
Thymomas are epithelial tumors of the thymus accounting for ~25 % of all mediastinal tumors.
They show a cytologically benign epithelial component and tend to remain encapsulated within the
thymus. A cytologically benign thymoma can invade and metastize to other sites and is termed
metastatic malignant thymoma.
Invasive thymomas are relatively rare tumors representing less than 1% of all malignancies. Most
patients with thymoma are aged 40 through 60 years and are asymptomatic at the time of
diagnosis. They may also present with cough, chest pain, superior venacava syndrome, and
dysphagia. Many patients also have myasthenia gravis (MG).
Metastatic malignant thymoma shows the typical biphasic cell pattern of a thymoma. The tumors
are predominantly epithelial, compared with the lymphoid component. In most cases, the epithelial
cells are predominantly of the epithelioid (cortical) cell type. The nuclei may be larger, and the
nucleoli more prominent, than in the epithelial component of ordinary thymoma. The presence of
cytologic atypia and numerous mitotic figures may correlate with more aggressive behavior.
However, invasion, not cellular morphologic characteristics, is the key to the diagnosis, and invasion
cannot be assessed cytologically.
Clinical History/Findings
The patient is a 26 year-old white male with a pleural nodule and a history of thymoma.
Specimen Type
An ultrasound guided fine needle aspiration biopsy (FNAB) and core biopsy of right paraspinal lesion
was performed.
Cytologic Findings
IHC Results:
Cytologic & Surgical Diagnosis:
Metastatic Malignant Thymoma
Commentary: These results are most consistent with metastatic malignant thymoma
as evidenced by the extensive invasion to the lung, thorax, and paraspinal lesions
and the dimorphic pattern of epitheliod and lymphocytic cells. The
immunohistochemical staining is consistent with a thymoma.
Submitted by:
Ann Marie West, BS, CT (ASCP)
Parkland Health & Hospital System
Dallas, Texas
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
| |
 |
Slide 1: A large cohesive
aggregate of epitheliod cells
admixed with a population of
lymphocytes.
aggregate of epitheliod cells
admixed with a population of
lymphocytes.
Slide 2: Large nuclei showing
irregular nuclear borders, prominent
nucleoli and variation in size and shape
common in metastatic thymoma.
irregular nuclear borders, prominent
nucleoli and variation in size and shape
common in metastatic thymoma.
Slide 3: Diff-Quik. Small
aggregate of cohesive epitheliod
cells.
aggregate of cohesive epitheliod
cells.
Slide 4: Positive For CD5
| The Texas Society of Cytology |
|
Slide 5: Positive For Cytokeratin
Slide 3: Tissue section showing
invasion of thymoma into the chest
wall. Similar findings were found
in diaphram and thorax.
invasion of thymoma into the chest
wall. Similar findings were found
in diaphram and thorax.
