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Page 2 of 16 De Iaco et al. Mini-invasive Surg 2020;4:63 I http://dx.doi.org/10.20517/2574-1225.2020.37

INTRODUCTION
Thymic neoplasms and malignancies are relatively uncommon. Approximately 90% of the tumors of
the thymus are thymoma, accounting for about 0.2%-1.5% of all cancers. The remaining 10% are thymic
carcinoma, carcinoid tumors, or lymphomas. Indications for thymectomy include suspected thymoma,
[1-4]
myasthenia gravis (MG) with and without thymoma, and thymic cists .
Radical thymectomy is the gold standard treatment for thymoma; in particular, completeness of surgical
[5,6]
resection and adequate margins are considered the most important prognostic factors . Complete surgical
resection of a well-encapsulated and noninvasive thymoma is usually curative, with low risks of local
[7]
recurrence . Invasive thymoma and thymic carcinoma could be treated with multimodal therapy including
induction or adjuvant chemo- or chemoradiotherapy associated with en-bloc surgical resection. Surgery is
[8]
also indicated for treatment of local recurrences and, in some cases, pleural and pericardial implants . To
achieve the most complete surgical resection, the International Thymic Malignancy Interest Group (ITMIG)
has suggested two surgical procedures for patients with or without MG [Table 1], respectively: extended
thymectomy, including the en bloc removal of the contiguous right and left mediastinal pleura, mediastinal,
and pericardiophrenic fatty tissues, and dissection of aorta-pulmonary window, in addition to complete
thymectomy [Figure 1] or complete thymectomy, including the en bloc removal of the upper cervical poles
[9]
and the surrounding mediastinal fat [Figure 2] .
Along with the en bloc resection of thymoma, a no-touch surgical technique should be performed; the
thymoma, in fact, should not be grasped or squeezed with retractors because of the possible rupture of the
[9]
capsule with subsequent pleural dissemination, as Kamel et al. demonstrated. Moreover, areas of potential
[10]
tissue disruption should be marked immediately during dissection on both the specimen and the patient .
Completeness of thymectomy should be assessed by macroscopic inspection of the thymic bed, specimen,
[11]
and subsequent pathological analysis . Complete resection (R0) is defined when there is no evidence of
residual tumor (macroscopically and/or microscopically) while incomplete resection is defined when there
is evidence of microscopically (R1) or macroscopically (R2) residual tumor. When dealing with thymomas,
there is often little tissue surrounding the tumor and quite often the capsule itself constitutes the outer
surface of the specimen, leading to misleading interpretations of the margins [Figure 3].

In such cases, only through-and-thorough penetration of the capsule by tumor which reaches the outer
[12]
surface should be interpreted as a positive margin . After an R0 resection or a complete radiographic
response has been previously achieved and an adequate 5-10 years of follow up has been carried out,
[10]
recurrence can be defined . Given the indolent behavior of many of these tumors, ITMIG has suggested
that freedom-from-recurrence (FFR), as calculated from the date of resection to the date of first recurrence,
[13]
is a better measure than survival in patients who have successfully undergone curative treatment .
Average recurrence rates are low for Masaoka Stage I tumors (3%) but increase progressively to 11% and
[14]
30% for Stage II and III tumors, respectively .
For years, the optimal surgical approach, combining the best degree of resection with minor surgical
invasiveness, has been discussed [15-18] . Minimally invasive approaches have become increasingly relevant
in the last two decades and a proved alternative to open techniques, which are still considered the gold
[19]
standard treatment because of technical advantages and proved good oncological results . According
[10]
to the above-mentioned general principles about radical thymectomies, ITMIG guidelines have been
proposed for minimally invasive resections. They should involve no rib spreading or sternal cutting,
dissection, and visualization of innominate vein, both phrenic nerves, and pleura in the case of suspected
invasion. Moreover, the access incision for retrieval should be large enough to prevent specimen disruption;
retrieval should always be done in the bag; and a correct examination of the removed specimen to assess
for completeness of the resection is required .
[10]