Myxoid liposarcoma of the scalp: case report and literature review

Differential diagnosis of soft scalp lumps

A 56-year-old man presented with a painless cyst on the top of his head which has been increasing in size in the last 6 months. Due to his learning disability, he could not be dissuaded from his belief that the lump was a sign of brain prolapse which led to increasing agitation in the next 2 weeks. A provisional diagnosis of benign lipoma was made and prompt excision was performed in his best interests. The lesion was more cystic and fluctuant than that of a lipoma and hence it was sent for histological diagnosis. The report came back as a trichilemmal cyst with no signs of proliferation. Cosmetic outcome was reasonable at follow-up after 3 months. The patient was scheduled for regular review every 6 months.

Mixed myxoid/round cell liposarcoma of the scalp

Liposarcoma of the head and neck is rare. Only 12 cases of scalp liposarcoma have been previously reported. In this report, we describe a case of myxoid/round cell liposarcoma in the scalp of a 28-year-old woman. This case report highlights a histologic pattern rarely reported in the head and neck but consistent with the evolving classification of liposarcomas.

Benign recurring lipoblastoma in an adult versus well differentiated subcutaneous myxoid liposarcoma: clinicopathologic, immunohistochemical and molecular analysis of a unique case

Subcutaneous myxoid liposarcoma (ML) is exceedingly rare, with only two or three cases having been reported. Lipoblastoma (LB), a rare fatty tumor that arises in infants and children, is unknown after adolescence. In contrast to ML, LB is often superficial. The two tumors can be difficult to distinguish due to many histologic similarities. We examined a 0.9 cm superficial subcutaneous nodule from the dorsal neck of a 48 year old man that had been growing slowly. Three and one half years later, a 0.4 cm palpable recurrent nodule was excised from the scar. The patient is now free of disease at 7.5 years. Because of these unusual features, we performed clinicopathologic, immunohistochemical and molecular analysis of this unusual tumor to decide if this represented a rare cutaneous ML or an unprecedented example of LB in an adult. The primary featured a thick fibrous pseudocapsule with foci of lymphocytes and infiltrating nests of semi-mature fetal-appearing adipocytic tissue. This surrounded a more immature cellular-but-cytologically-bland myxoid tissue featuring stellate cells and signet lipoblasts. There were fibrous sep at the periphery and the vasculature was rather inconspicuous. The 0.4 cm diameter recurrence was distinctly lobular and had minute satellite nodules. It was composed of uniform fetal-appearing bland myxoid lipoblastic tissue featuring signet ring lipoblasts surrounded by a few spindle cells. In both tumors, lipoblasts expressed S-100 protein. In the primary, 5% of the lesional cells were FXIIIa+ dendritic stromal histiocytes while in the recurrence, 15% of the lesional cells were FXIIIa+ dendritic cells. CD34 stained only scattered small capillaries. The Ki67 proliferation index was 1% in the primary and 3% in the recurrence. RT-PCR assay for TLS/FUS-CHOP fusion transcripts was negative despite three repeat tests performed on paraffin sections of the primary tumor in the presence of good m-RNA internal controls. We reviewed the clinicopathologic and cytogenetic features of ML and LB. Based on this review and on the growth pattern, anatomic features and molecular data from the present case, we conclude that this tumor may represent the first reported case of adult LB.