Primary Angiomatoid Melanoma as an Exceptional Morphologic Pattern in Cutaneous Melanoma. A Case Report and Review of the Literature

Abstract

We report a case of angiomatoid melanoma on the right thigh of a 59-year-old man. The histologic growth pattern of the tumor mimicked vascular proliferation, and the cells lining the pseudovascular spaces were positive for protein S-100, HMB-45, and MITF-1. The differential diagnosis is with angiosarcoma and pseudovascular adenoid squamous cell carcinoma. The case we present is the fifth reported to date.

Primary cutaneous angiomatoid melanoma

“…As in our case, the lesion on the forehead showed clusters of HMB-45 and S-100-positive cells forming vascular channels [4]. Since then, four more cases with similar histopathology have been published [2,3]. A vessel-like morphology with pseudovascular channels has also been described in other melanocytic neoplasms [5,6]; here, due to the lack of tissue resistance to traction, vascular spaces may be formed as a result of the biopsy procedure.…”

“…As in the present case, angiomatoid melanoma usually shows an aggressive behavior. While it tends to exhibit metastatic histological features [3,4], there are at least two reports of primary angiomatoid melanoma, as in our patient [2,3].…”

“…Cutaneous melanoma is characterized by clinical and histopathological variants, the latter including an increasing number of different designations [1] (including nevoid, follicular, animal, spitzoid). Rarely reported in the literature, angiomatoid pattern is an extremely uncommon histological melanoma variant [2,3]. It was first described by Adler et al in 1997 in a patient with cutaneous metastatic melanoma of unknown origin [4].…”

Angiosarcomatous transdifferentiation of metastatic melanoma

“…Different types of divergent differentiation have been described including fibroblastic/myofibroblastic, schwannian and perineurial, smooth muscle, rhadbomyosarcomatous, osteocartilaginous, ganglionic and ganglioneuroblastic, neuroendocrine, and epithelial 1,2 . Malignant melanomas mimicking angiosarcoma have been described, but to our knowledge true divergent differentiation into angiosarcoma has never been reported in the literature 3 . In this paper, we present such a case.…”

Index report of cutaneous angiosarcomas with strong positivity for tyrosinase mimicking melanoma with further evaluation of melanocytic markers in a large angiosarcoma series

“…Those composed purely of vasoformative areas with irregular anastomosing vessels, lined by atypical hobnail cells, sometimes with multilayering and formation intraluminal papillae, are more easily recognized. However, other tumors can display pseudoangiomatous growth including melanoma, which can have cavernous pseudovascular channels containing erythrocytes and lined by atypical dyshesive cells (angiomatoid melanoma) . Angiosarcomas with poorly differentiated histology are often composed of solid areas with sheets of spindled, epithelioid and pleomorphic cells without apparent vascular differentiation.…”