Carcinoma ex-pleomorphic adenoma of the salivary glands has a high risk of progression when the tumor invades more than 2.5 mm beyond the capsule of the residual pleomorphic adenoma

Carcinoma ex-pleomorphic adenoma (CPA) is subclassified based on the extent of penetration of the malignant component beyond the fibrous capsule of the pre-existing pleomorphic adenoma (PA). These subclasses are considered to be prognostically significant since the non-invasive/minimally invasive groups have an excellent outcome. Nevertheless, there is no consensus as to the cutoff value to distinguish between minimal and wide invasion, even though the 2005 WHO classification defines 1.5 mm as cutoff. The objective of this study is to evaluate a consecutive series of CPA, in order to establish what the effect is of the extent of extra-capsular invasion on prognosis. Fifty-eight cases of CPA were reviewed to obtain demographic and pathological information. Extent of invasion was measured. Eleven cases were non-invasive, 9 had ≤1.5 mm invasion, and for the remainder, the depth of invasion ranged between 2.5 and >10 mm. Distant metastases or death did not occur in the first two groups. In the group with ≥2.5 mm invasion, 15 patients had progressive disease and 9 of them died. The minimum extent of invasion associated with tumor progression and death was 2.5 mm. Two histologically non-invasive carcinomas had regional lymph node metastasis. CPA with ≤1.5 mm depth of invasion has good prognosis. Nevertheless, the lymph node metastases found in two cases of this group question the concept that intracapsular/minimally invasive CPA has a prognosis similar to that of PA. The minimum extent of invasion associated with death was 2.5 mm, which is at variance with findings in other recent series. Thirteen cases with depth of invasion exceeding 2.5 mm did well, confirming that additional factors should be considered in the clinical management of these patients.