Pseudomyogenic (epithelioid sarcoma-like) hemangioendothelioma - a rare vascular neoplasm with deceptive morphology and distinctive immunophenotype.

Pseudomyogenic (epithelioid sarcoma-like) hemangioendothelioma is a rare, low grade vascular (endothelial) neoplasm typically presenting as multicentric, superficial to deep nodules in extremities with a slight tendency of affecting young adult males. We report a case of pseudomyogenic hemangioendothelioma in a 15-year-old boy presenting initially with a 1 cm right thigh painless cutaneous lump. The lump was excised with the clinical impression of a sebaceous cyst. On microscopy, a poorly circumscribed, mild to moderately atypical spindle cell lesion in fascicular and storiform patterns with strikingly myoid-like eosinophilic cytoplasm was identified. The spindle cells were highlighted by pancytokeratin AE1/AE3, CD31, and ERG with retained INI-1, while being negative for MNF116, S100, CD34, EMA, desmin, SMA, caldesmon, myogenin, MyoD1, HHV-8 and CD163. Following the first diagnostic report, a positron emission tomography-computed tomography (PET-CT) scan revealed another 4 cm ill-defined nodule accompanied by a smaller adjacent 0.7 cm ipsilateral satellite nodule within the right psoas muscle that displayed similar morphology and immunophenotype as the cutaneous lump, supporting the multicentric feature of this unique entity. It is an uncommon yet increasingly recognised neoplasm of endothelial origin possessing a misleading myoid morphology and distinctive immunophenotype worth notifying.

Diagnosing a rare case of desmoplastic small round cell tumour on liver biopsy.

A 50-year-old male of Indian descent presented with jaundice and right hypochondrium pain. Following a computed tomography (CT) scan of the abdomen, a segment 7 liver lesion was visualized, accompanied by extensive peritoneal tumour deposits. An ultrasound guided liver biopsy was performed and histology showed loose nests and sheets of tumour cells with a small blue round cell morphology. The tumour cells showed patchy strong immunopositivity for cytokeratins (AE1/3, CK7, CK19) and synaptophysin, while showing diffuse strong perinuclear positivity for desmin. Interphase fluorescence in-situ hybridization (FISH) study using EWSR1 breakapart probe was positive for EWSR1 gene rearrangement. Desmoplastic small round cell tumour is a rare but aggressive intra-abdominal mesenchymal tumour. While the primary sites of involvement are usually the peritoneum and omentum, visceral involvement can occur. We wish to highlight the importance of considering this entity when evaluating a liver biopsy especially in a less than classical clinical context.