Prior to 1976:

Any tumor of the thymus gland was referred to as a “thymoma”

true epithelial tumors
thymic carcinoma
seminoma
lymphoma

• Rosai & Levine then defined the modern classification

• the functional unit of the thymus gland is the Lobule

• • composed of a cortex & medulla

  • epithelial cells

  • lymphocytes

Thymomas are, by definition, primary tumors of benign-appearing thymic epithelial cells

• Given this definition, most thymomas are “benign”

• • the majority behave in an indolent fashion

  • however, they can invade and metastasize (uncommon)

  • when a thymoma is contained within the thymic capsule, it is referred to as “benign” or “noninvasive”

  • when it penetrates through the capsule, it is referred to as “malignant” or “invasive”

Thymic tumors composed of truly-malignant-appearing epithelial cells are now referred to as thymic carcinoma

• rare event

• accounts for less than 10 % of all primary thymic tumors

• locally aggressive & metastasize hematogenously

• poor overall prognosis

In 1985:

A revised histologic classification system

• based primarily on the relation of tumor histology

• not on the degree of cellular atypia

• confusing and unclear metabolic behavior

• controversial etiology & development

• vague natural history & unknown incidence

Some Points

“A Mass in the Anterior Mediastinum”

Diagnostic studies: CXR & C.T. scan

Thymoma Symptoms

Staging

The most important factor in determining prognosis is the tumor stage at time of operation, which is best described by macro-invasiveness by the surgeon of record

• Stage I, II, & IIb: macroscopically negative

• Stage III, IVa, & IVb: macroscopically-invasive

• Biopsy or “No-Biopsy”

• • 85 % of patients will present with resectable disease and should proceed to extended thymectomy regardless of the biopsy result

  • these patients should be taken to the operating room without a tissue diagnosis and undergo en-bloc resection

  • patients with radiographic-unresectable disease may be candidates for open biopsy or core-biopsy

Surgical resection is the mainstay of treatment for thymoma

Following clinical stage, the most important determinant of recurrence is the ability of the operating surgeon to achieve a complete resection at the initial operation

• Extended-resection, 5-yr. Survival: 80 - 98 %

The Extended Thymectomy

A direct mediastinal approach to allow for the en bloc removal of all cervical & mediastinal soft tissue, including the thymus, mediastinal pleura, adjacent perithymic fat, epiphrenic, & perithyroidal tissue

• removes 95 - 98 % of all thymic tissue

• based on Jaretzki's study of thymic-origin

• Other Surgical Approaches

• • Transcervical Thymectomy

  • Video-assisted Thymectomy

  • Partial-mediastinal-debulking

• Operative mortality in most series is 0 - 1 %

• Permanent injury to the Phrenic or Recurrent nerves: 1 %

• Most common complications: arrythmias, residual ptx, effusions

Other Modalities of Treatment

• Primary Radiotherapy: “unresectable tumor” / SVC-syndrome

• Adjuvant Radiotherapy: the standard of care for thymoma

• • thymomas are well-known to be radiosensitive

  • decreases recurrence by 5-fold across the board

• Chemotherapy:

• • glucocorticoids & platinum-based agents

  • controversial / lack of long-term trials

Myasthenia Gravis

Question: What is the “” ?

Question: Who was the first to report his surgical experience with myasthenia gravis ?