Juan Rosai Memory - Thymomas Classification.

Introduction Thymomas classification dates from 1976 Juan Rosai/Gerald Levine established the epithelial nature of the "thymoma" and correlated morphology and biological behaviour with the degree of thymus capsule invasion at surgery. Surgical staging was fundamental for the subsequent classification of Masaoka et al in 1981, still commonly used in routine. Muller-Hermelink Histogenetic Classification (1999) supported WHO 2004/2014 classification, allowing the actual naming Thymomas in A and/or B typing. Overall survival for types AB and B1 Thymomas is very good - 80-100% at 5 and 10 years and for type B2, 70-90% at 10 years has seen recognized. Objectives Juan Rosai (August 20, 1940 - July 7, 2020) legate calls attention for the actual 2014 WHO thymomas classification. A broad morphology recognition is demanded instead of a single cut apart language - case report of a Thymoma AB, with B1 and B2 components. Materials and Methods Solid 11,3x7cm antero-superior mediastinum mass detected at CT was proposed for surgical removal in a 65-years old woman hospitalized suspecting of Rickettsial infection. Results Surgical specimen weighing 329g and measuring 12x9x7cm, delimited by thymus thin and shiny capsule showed tumoural cut surface, vaguely lobulated, tan to pink and smooth. Microscopic evaluation detected two intermingled different components: a clear nodular pattern with bland spindle cells bundles - thymoma A, interspersed with B pattern where quantity variable population epithelial superimposing T cells (CD3+) defined patterns of thymomas type B1 and type B2. Conclusions Thymomas are a rare malignancy in general, but the most common mediastinal tumours in adults over fourties, with type AB as the most common, between 11 and 89 years old followed by type B2 and B1. Type AB thymoma encompasses poverty of lymphocytes over spindle cells (type A) besides other epithelial component rich in T lymphocytes (type B). In the present a case it was possible to subtype B component thymoma in either B1 and B2 by applying 2014 WHO recommendations. Taking into account Type B2 thymoma poorer outcome compared to Type AB and Type B1 thymomas, it is important to differentiate and subtype B component when present, to preview of possible therapeutic strategies in follow up. No etiologic factor has been still attributable for the appearance of this kind of neoplasia, but there are some reports and putative thymic epithelial cells precursors.