Tanas, Munir R.

Aims Limited data exist on atypical lipomatous tumour (ALT)/well‐differentiated liposarcoma (WDL) and de‐differentiated liposarcoma (DDLPS) in children and young adults. Methods and results Cases of ALT/WDL/DDLPS arising in patients aged ≤ 40 years were collected from multiple institutional and consultation archives. A total of 116 cases of ALT/WDL (75) and DDLPS (41) were identified, representing fewer than 5% of these tumours seen at our institutions during this time‐period. The patients (59 male/57 female) ranged in age from 8 to 40 years. Sites included deep central (abdomen/retroperitoneum/pelvis/groin) ( n = 60), extremity ( n = 42), trunk ( n = 5), head/neck ( n = 8) and mediastinum ( n = 1). De‐differentiated patterns included: high‐grade pleomorphic sarcoma, myxofibrosarcoma‐like, heterologous rhabdomyoblastic differentiation, low‐grade spindle cell sarcoma and homologous lipoblastic differentiation. Forty‐one patients experienced a local recurrence and 11 patients with DDLPS developed metastasis. ALT arising in the extremities had lower recurrence rates than deep central WDL (5‐year recurrence‐free survival 88.9% versus 59.0%; P = 0.002), while patients with deep central DDLPS experienced significantly more adverse events compared to WDL at this site (5‐year event‐free survival 11.9% versus 59.0%) ( P < 0.0001). Seven (of eight) head/neck tumours had follow‐up available; five recurred, and one patient (DDLPS) with recurrence also experienced a metastasis. The single mediastinal tumour (DDLPS) recurred and metastasised. Conclusion ALT/WDL and DDLPS occurring in patients aged ≤ 40 years is rare, but exhibits similar morphological features to its counterparts in older adults, including potential for heterologous and homologous de‐differentiation in the latter. Although case numbers are limited, tumours arising in the head and neck exhibit high rates of adverse events, suggesting that classification as WDL rather than ALT is more appropriate.

Objectives. Desmoplastic small round cell tumor (DSRCT) is an aggressive round cell sarcoma that arises in the abdominal cavity/pelvis of young males. We sought to expand its clinicopathologic spectrum. Methods. Cases of DSRCT presenting in patients >30 years of age or tumors arising outside of the abdominal cavity/pelvis were retrieved. Results. Thirty-four cases were identified. Sixteen tumors arose at atypical sites (head/neck, intracranial, thigh, axilla/shoulder, inguinal/paratesticular, intraosseous, and uterine corpus). The remaining 18 patients were older than 30 years, and their tumors involved the abdomen or pelvis. The majority of cases showed areas with classic histology, while 6 cases exhibited solid growth and 5 showed macronodular architecture. Cytologic appearance included round cell, rhabdoid, epithelioid, and small cell. Conclusion. DSRCT may arise at nonabdominal locations in both pediatric and adult populations, as well as intra-abdominally in older adults, and these tumors exhibit high rates of metastasis and morbidity.

AimsEpithelioid haemangioendothelioma (EHE) is a malignant vascular neoplasm. Subsets have been characterized previously by translocations resulting in either WWTR1–CAMTA1 or YAP1–TFE3 fusion. We sought to develop molecular and immunohistochemical (IHC) assays to aid in the diagnosis and characterization of EHE.Methods and resultsFifty‐two formalin‐fixed, paraffin‐embedded (FFPE) cases diagnosed between 2002 and 2014 were retrieved from the pathology files of our institutions. Reverse transcription–polymerase chain reaction (RT–PCR) assays were optimized to detect WWTR1–CAMTA1 and YAP1–TFE3 fusion transcripts in FFPE tissue and transcription factor E3 (TFE3) protein accumulation was examined by immunohistochemistry (IHC). RNA was extracted from 33 adequate samples, with more recent cases providing a greater yield of high quality RNA. Fourteen of 18 informative cases were positive for WWTR1–CAMTA1 fusion transcripts, four of which showed higher‐grade cytological features termed by some as ‘malignant EHE’. Novel in‐frame fusion transcripts were identified in four cases by direct sequencing. IHC revealed variable nuclear TFE3 staining in six of 17 cases; three with patchy staining showed WWTR1–CAMTA1 fusion. One of 18 informative cases was positive for YAP1–TFE3 fusion and showed strong nuclear TFE3 staining by IHC.ConclusionsThis study confirms the high incidence of WWTR1–CAMTA1 and YAP1–TFE3 rearrangements in EHE and indicates that the staining pattern for TFE3 IHC is critical for specificity.

A newly identified gene fusion defines the vascular cancer epithelioid hemangioendothelioma and encodes a chimeric transcription factor.