David R. Lucas

Context.—: Liposarcoma is divided into myxoid, pleomorphic, well-differentiated, and dedifferentiated subtypes. Dedifferentiated liposarcoma displays the greatest histomorphologic diversity, including a subset with myofibroblastic differentiation that shares similarities with a spectrum of reactive, benign, and malignant soft tissue lesions. Misdiagnosis may lead to deleterious consequences, as dedifferentiated liposarcoma differs significantly in its prognosis and treatment from its mimics. Objective.—: To review the clinicopathologic, immunohistochemical, and molecular features of the myofibroblastic variant of dedifferentiated liposarcoma as well as the key distinguishing features from its mimics. Data Sources.—: Review of pertinent literature on major features and current understanding of dedifferentiated liposarcoma with myofibroblastic differentiation. Conclusions.—: The myofibroblastic variant of dedifferentiated liposarcoma is an uncommon and underrecognized sarcoma with several important differential diagnoses, and likely represents the major subset of aggressive retroperitoneal tumors that may have been misdiagnosed as desmoid-type fibromatosis, inflammatory myofibroblastic tumor, or another type of sarcoma in the past.

Myxoinflammatory fibroblastic sarcoma is a rare soft tissue tumor with most occurring in the distal extremities of adult patients. It has a high rate of local recurrence and a low rate of metastasis. Because it may appear benign on clinical examination, and because the microscopic features are generally underrecognized, it is often inadequately treated and misdiagnosed. In this review, based upon experience and that of the literature, the intent is to highlight salient clinicopathologic features, detail the broad microscopic spectrum including high-grade aggressive variants, review the molecular features, and discuss its relation to hemosiderotic fibrolipomatous tumor.

Tenosynovial giant cell tumors are a group of generally benign intra-articular and soft tissue tumors with common histologic features. They can be roughly divided into localized and diffuse types. Localized types include giant cell tumors of tendon sheath and localized pigmented villonodular synovitis, whereas diffuse types encompass conventional pigmented villonodular synovitis and diffuse-type giant cell tumor. Localized tumors are generally indolent, whereas diffuse tumors are locally aggressive. Recent developments indicate that tenosynovial giant cell tumors are clonal neoplastic tumors driven by overexpression of CSF1. Herein, I report a case of intra-articular, localized tenosynovial giant cell tumor (or localized pigmented villonodular synovitis) and review the classification, histopathology, and recent developments regarding its pathogenesis.

Osteoblastoma is a rare benign bone tumor. Although the histologic features in most cases are distinctive, there are various permutations that make the diagnosis challenging. It can mimic a variety of other benign bone tumors, but more importantly, distinguishing it from osteoblastoma-like osteosarcoma can be difficult. In this case report, I describe the clinicopathologic findings for a 13-year-old adolescent boy with T7 spinal osteoblastoma and review salient clinical, radiographic, and pathologic features of osteoblastoma, as well as the differential diagnoses.

Osteoblastoma is a rare benign bone tumor. Although the histologic features in most cases are distinctive, there are various permutations that make the diagnosis challenging. It can mimic a variety of other benign bone tumors, but more importantly, distinguishing it from osteoblastoma-like osteosarcoma can be difficult. In this case report, I describe the clinicopathologic findings for a 13-year-old adolescent boy with T7 spinal osteoblastoma and review salient clinical, radiographic, and pathologic features of osteoblastoma, as well as the differential diagnoses.

The dedifferentiated component of dedifferentiated liposarcoma shows wide histologic variation including tumors with heterologous differentiation. Myofibroblastic differentiation has been recognized in dedifferentiated liposarcoma. However, tumors closely resembling inflammatory myofibroblastic tumor have not. We report the clinicopathologic, immunohistochemical, and molecular finding in 6 cases of dedifferentiated liposarcoma with inflammatory myofibroblastic tumor-like features treated at our institution. The tumors occurred mostly in middle age or elderly men, involved mostly the inguinal/scrotal region or retroperitoneum, and behaved aggressively. Microscopically, the dedifferentiated component closely resembled or, if taken out of context, was indistinguishable from inflammatory myofibroblastic tumor. All 3 major patterns seen in inflammatory myofibroblastic tumor (myxoid, cellular, and hypocellular fibrous) were represented. Areas resembling nodular fasciitis or desmoid fibromatosis were frequent findings. One tumor had heterologous osseous differentiation. In 4 tumors the inflammatory myofibroblastic tumor-like areas were diffuse, whereas in 2 they were combined with noninflammatory myofibroblastic tumor-like high-grade sarcoma. Five tumors stained for smooth muscle actin or desmin, none stained for ALK-1, 5 stained for MDM2, and 5 had amplified MDM2 by fluorescence in situ hybridization. Well-differentiated liposarcomatous components were present in every tumor. All patients developed locally recurrent or metastatic disease. At last follow-up 2 patients had died of disease and 2 were alive with disease. Dedifferentiated liposarcoma can have prominent inflammatory myofibroblastic tumor-like features, a finding that further expands its histologic spectrum. Awareness of this finding can prevent one from misdiagnosing dedifferentiated liposarcoma as inflammatory myofibroblastic tumor, a much less aggressive neoplasm.

Mankey C C, McHugh J B, Thomas D G & Lucas D R (2010) Histopathology 56, 364–371 Can lymphangiosarcoma be resurrected? A clinicopathological and immunohistochemical study of lymphatic differentiation in 49 angiosarcomas Aims:  The term lymphangiosarcoma has largely been abandoned in the current classification of endothelial neoplasms. Recently, a number of lymphatic‐associated antibodies have been developed for immunohistochemistry, which frequently stain angiosarcomas, implying lymphatic or mixed lymphatic and blood vascular differentiation is common. The aim was to investigate further lymphatic antigen expression, and to explore the relation of immunohistochemistry to morphological and clinical findings.Methods and results:  Forty‐nine angiosarcomas in tissue microarrays were analysed with D2‐40 and antibodies to Prox‐1 and vascular endothelial growth factor receptor (VEGFR)‐3. D2‐40 was positive in 53%, Prox‐1 in 76%, and VEGFR‐3 in 57%. Tumours with features attributable to lymphatic differentiation such as hobnail and kaposiform morphologies were more often positive with these markers, including a statistical association between D2‐40 and hobnailing. Ten tumours had features suggestive of lymphatic differentiation, namely well‐differentiated histology, interanastomosing channels devoid of red cells, prominent hobnailing, lymphoid aggregates, and multi‐antigen expression of D2‐40 (100%), Prox‐1 (100%) and VEGFR‐3 (60%), which might be deserving of the appellation lymphangiosarcoma. Nine were cutaneous scalp/facial tumours in elderly patients and one arose within chronic lymphoedema.Conclusions:  Lymphatic differentiation is common in angiosarcoma, certain subsets show greater lymphatic differentiation than others, and lymphangiosarcoma may be defined pathologically, rather than clinically.

Osteomas are limited almost exclusively to craniofacial and jaw bones. Histologically, they can be divided into ivory, mature, or mixed types. Osteomas may have osteoblastoma-like areas and distinguishing it from true osteoblastoma can be challenging. Some believe osteomas with osteoblastoma-like features behave more aggressively. To perform a clinicopathologic comparison of sino-orbital osteomas both with and without osteoblastoma-like features. We studied 45 surgically excised sino-orbital osteomas. Tumors were categorized as ivory, mature, or mixed type and presence of osteoblastoma-like areas and Paget-like bone were noted. Clinical features of those with and without osteoblastoma-like areas were compared. Men outnumbered women (3:2); median age was 37 years. Frontal sinus was the most common location (62%) followed by ethmoid and maxillary sinuses. Twelve tumors (27%) involved the orbit, 2 primarily and 10 secondarily. All cases were symptomatic with headache, sinusitis, visual changes, pain, and proptosis being most common. Seventeen tumors (38%) had osteoblastoma-like areas. Extension into an adjacent sinus/anatomic compartment was more common in osteoblastoma-like tumors (47% versus 29%), including more frequent orbital involvement (41% versus 13%). Visual changes were more frequent in the osteoblastoma-like group. Distribution of histologic subtypes and Paget-like bone were similar between the 2 groups. Osteomas with osteoblastoma-like features were more often incompletely excised (25% versus 14%). However, clinical recurrence was less common (8% versus 27%). Osteoblastoma-like features are common in sino-orbital osteomas, but it does not correlate with more adverse clinical features or worse outcome. Osteoblastoma-like areas appear to represent active remodeling within an osteoma rather than defining a distinct clinicopathologic entity. Distinguishing it from osteoblastoma may require careful histologic evaluation and radiographic correlation.