Key diagnostic features of additional soft tissue neoplasms

Chapter 20a

Key diagnostic features of additional soft tissue neoplasms


Images appear in the accompanying soft tissue atlas.

Atypical vascular lesion (AVL)

Atypical vascular lesion is generally located on the breast and appears several years after irradiation. Clinically, the lesions are initially small purple-pink to red-brown multifocal papules that are well circumscribed histopathologically. While initially described as benign (acquired progressive lymphangioma or benign lymphangiomatous papules of the skin), many authors now consider these lesions to be potential precursors of angiosarcoma. Thus, close clinical follow-up or sometimes complete excision has been recommended. Amplification of MYC and FLT4 expression suggests a diagnosis of angiosarcoma rather than AVL.

Microscopically, there is a spectrum of “more banal to more worrisome”. Banal lesions appear well-delimited in the superficial dermis, with non-atypical endothelial cells in a single layer lining vessel lumens with minimal luminal anastomosis. More worrisome lesions show deeper, infiltrative involvement of the dermis with anastomosing vessels. Features that are absent include significant cytologic atypia, papillated endothelial cells, and lakes of blood. Such findings would be suspicious for angiosarcoma.

Carcinosarcoma (biphasic)

Carcinosarcoma is composed of two different malignant cell types: epithelial and mesenchymal spindle cells. Examples of carcinosarcoma in the skin include tumors with foci of basal cell carcinoma or squamous cell carcinoma intimately associated with a malignant spindle cell population that is negative with keratin stains. This spindle cell population sometimes has some resemblance to the cells of atypical fibroxanthoma. The differential diagnosis includes other malignant epithelial and spindle cell tumors, with the key to carcinosarcoma being recognition of the close admixture of two different malignant cell types.

Extra-abdominal desmoid (extra-abdominal fibromatosis)

Extra-abdominal desmoids originate from the fascia and connective tissue surrounding muscles, especially in the shoulder/pelvic girdle/thighs. Adolescents and young adults are most commonly affected. Although less common in children, extra-abdominal desmoids can present on the head/neck in this age group. Tumors can be multicentric and large and erode into bone or other nearby structures. Histologic findings include slender, elongated, bland spindle cells that are separated by collagen in long fascicles. Tumor cells may infiltrate surrounding structures, especially striated muscle. Tumor cell differentiation is fibroblastic/myofibroblastic, as suggested by positive staining with smooth muscle actin and muscle-specific actin and, rarely, desmin. Tumor cells are also positive with beta-catenin. The main differential diagnosis includes fibrosarcoma and reactive fibroblastic/myofibroblastic proliferations.

Apr 26, 2016 | Posted by in Dermatology | Comments Off on Key diagnostic features of additional soft tissue neoplasms
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