cutaneous myxoma

WKP

PO

Definition: A cutaneous myxoma, a.k.a. superficial angiomyxoma, consists of a multilobulated myxoid mass containing stellate or spindled fibroblasts with pools of mucin forming cleft-like spaces. There is often a proliferation of blood vessels and an inflammatory infiltrate.

Synopsis

 hypocellular tumors / hypocellularity
 composed of bland cells,
 no mitotic activity,
 no lipoblasts,
 scant blood vessels;
 may have focal histiocytes
 Slightly more cellular with collagenized capsule at periphery
 May have areas of increased vascularity or be hypercellular (Am J Surg Pathol 1998;22:1222)
 Slightly basophilic matrix with usually a few spindle cells at high power with oval nuclei
 May have central mucinous cyst
 At periphery, may infiltrate striated muscle and be associated with muscle atrophy

Immunochemistry

Immunostaining is :
 positive for vimentin ,
 negative for cytokeratin and desmin ,
 variable for CD34 (50%), Factor VIIIa , SMA , MSA and S-100.

Clinically, it may present as solitary or multiple flesh-colored nodules on the face, trunk, or extremities. Local recurrence is common.

It may occur as part of the Carney complex , and is sometimes the first sign.

Differential diagnosis : cutaneous myxoid tumors

Myxoid or mucinous background change is a common finding in a wide variety of cutaneous tumors and other diseases.

Myxoid tumors often have overlapping features and may show significant heterogeneity from area to area within a given specimen and from individual case to case.

As prognosis and treatment vary considerably between many of these entities, accurate diagnosis is essential.

Myxoid tumors include :
 superficial angiomyxoma (cutaneous myxoma )
 superficial acral fibromyxoma (digital fibromyxoma )
 dermal nerve sheath myxoma (conventional neurothekeoma )
 myxoid dermatofibrosarcoma protuberans ,
 giant cell fibroblastoma ,
 low-grade fibromyxoid sarcoma ,
 myxofibrosarcoma ,
 myxoinflammatory fibroblastic sarcoma

Molecular biology

 GNAS1 mutations in 61% of intramuscular myxomas (Mod Pathol 2009;22:718)
 No cytogenetic aberrations

See also

 angiomyxoid tumors
 cutaneous tumors
 myxomas