Atypical Placental Site Nodule (APSN) and Association With Malignant Gestational Trophoblastic Disease; A Clinicopathologic Study of 21 Cases

Abstract

The WHO Classification of Gestational Trophoblastic Tumors classifies placental site nodule (PSN) as a benign tumor-like trophoblastic neoplasm. Cases of PSN with atypical features were described [atypical placental site nodule (APSN)] and we started registering APSN in our unit in 2005. The aim of this study is to present our initial experience with these lesions. The Trophoblastic Disease Unit database was searched to identify all patients who were either referred with, or on review were diagnosed with, APSN from September 2005 to May 2013. Case notes and the pathology findings for these patients were retrieved and reviewed. A total of 21 cases of APSN were included, 3 of which were associated with gestational trophoblastic neoplasm on follow-up or review. Malignant gestational trophoblastic disease was associated with 3/21 (14%) cases of APSN, either concurrently or developing/manifesting within 16 mo of APSN diagnosis. None of these patients had raised serum hCG levels either at presentation or follow-up. Presence of APSN should indicate a thorough clinical and radiologic investigation and follow-up if diagnosed on curettage specimens. With increased recognition of this entity and corresponding larger series with longer follow-up, more accurate patient counseling will be possible.

Update on the diagnosis and management of gestational trophoblastic disease

“…ETT may coexist with choriocarcinoma or PSTT [10][11][12]. Emerging data indicate that atypical placental site nodules (APSN) can co-exist and/or preceded ETT and PSTT, suggesting that at least APSN cannot be regarded as benign [13].…”

Gestational Trophoblastic Tumors: A Timely Review of Diagnostic Pathology

“…56 In the most recent series of 21 APSNs, 3 patients had concurrent or subsequent malignant trophoblastic tumors: 1 patient had concurrent APSN and PSTT, 1 patient developed PSTT after 16 months, and 1 patient received a diagnosis of ETT 6 months after the diagnosis of APSN. 57 Therefore, it is clinically relevant that patients with APSN should undergo imaging studies to rule out underlying mass lesion and require clinical follow-up, including serum hCG measurement.…”

Update on the pathology of gestational trophoblastic disease

“…The histologic features of the APSN were intermediate between PSN and PSTT/ETT, with lesions larger than the usual PSN, which rarely exceed 4 mm. APSNs also had increased cellularity, mild atypia, and an increased ki‐67 index compared to usual PSN .…”

“…). A potential pitfall, although rare, are atypical placental site nodules (APSN) . On one series, 3/21 lesions termed APSN were associated with GTD on follow‐up, developing into either PSTT or ETT.…”