Patel, Nimesh R.

Nodular fasciitis is a benign self‐limited myofibroblastic neoplasm, which usually involves the upper extremities and trunk of young patients. These tumors have been shown to harbor a translocation involving the MYH9 and USP6 genes, leading to overexpression of the latter. We report seven cases of nodular fasciitis with cutaneous presentations. All cases involved the dermis, with six involving the superficial subcutis, and one auricular tumor extending into cartilage. All cases showed USP6 rearrangement by fluorescence in situ hybridization; in two of three cases, the characteristic MYH9‐USP6 fusion was shown by RT‐PCR. All patients underwent conservative resection. Nodular fasciitis is an uncommon mesenchymal neoplasm that can occasionally present in superficial locations and is sometimes mistaken for a malignant process. Molecular testing can be useful to distinguish this entity from other cutaneous spindle cell tumors.

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.