A 63-year-old woman presented with persistent postmenopausal bleeding. MRI of the pelvis showed a 6.3 cm uterine mass. The patient underwent total hysterectomy and bilateral salpingo-oophorectomy with bilateral pelvic sentinel biopsies.
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Mesonephric-like adenocarcinoma (MLA) is a recently recognized aggressive adenocarcinoma variant of the uterine corpus and ovary. Patients often present at advanced stage. MLA has a propensity to metastasize to the lung.
Morphologically, MLA exhibits heterogeneous architectural growth, including a mixture of tubular, papillary and slit-like patterns. Tubules frequently contain intraluminal eosinophilic secretions. The nuclear features are low grade and can resemble papillary thyroid carcinoma by the presence of angulated nuclei and occasional nuclear grooves.
The typical MLA immunophenotype consists of expression of TTF1 and GATA3 with limited to no expression of ER and PR. This immunoprofile assists in their distinction from endometrioid carcinoma.
MLA of the uterine corpus has considerable morphologic and immunohistochemical overlap with mesonephric adenocarcinoma of the cervix, with a significant distinguishing feature being MLA lacks associated mesonephric remnants or hyperplasia (Wolffian structures located predominantly in the para-ovarian region and deep in the lateral aspect of the cervix).
MLA and mesonephric adenocarcinoma exhibit similar molecular aberrations consisting of KRAS mutations, gain of chromosome 1q, 10 and 12, and lack of PTEN alterations. PIK3CA mutations are also found in MLA, providing evidence of both mesonephric and Mullerian differentiation.
Farah Baban, M.B., Ch.B.
Fellow, Anatomic and Clinical Pathology
J. Kenneth Schoolmeester, M.D.
Consultant, Anatomic Pathology
Assistant Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science