Type III cutaneous atypical meningioma of the scalp.

Meningiomas occur rarely in extracranial sites, including the skin, where they may pose a diagnostic challenge because of their histopathologic overlap with several other spindle-cell tumors. Cutaneous meningiomas are divided into type I (congenital), type II (ectopic), and type III (via direct extension) lesions. We present a rare case of atypical meningioma of the skin in a 71-year-old woman who presented with a painful and enlarging lesion on the left central frontal scalp. Biopsy showed bone and soft tissue with involvement of a spindle cell neoplasm, consisting of whorled nests with atypical features, including variably increased mitotic index, areas of hypercellularity, and sheeted architecture. The overall findings were consistent with an atypical meningioma (World Health Organization grade 2). Atypical meningiomas constitute only 5% to 15% of all meningiomas. Magnetic resonance imaging of the skull later demonstrated a left frontal tumor consistent with an atypical meningioma that had eroded through the skull. Dermatopathologists should consider cutaneous meningioma as a differential diagnosis of spindle-cell neoplasms of the skin and subcutaneous tissue in head and neck.

Primary cutaneous histiocytoid carcinoma with distant metastasis.

Distinguishing primary cutaneous adnexal carcinoma from metastatic carcinoma of unknown primary can be a diagnostic challenge due to the frequent overlap of histologic and immunohistochemical features. A 58-year-old man presented with a tender, indurated plaque on axillary skin. Biopsy revealed infiltrating atypical cells throughout the dermis, without connection to the epidermis. Tumor cells had a histiocytoid appearance and displayed mild pleomorphism. The tumor was discohesive and had areas with a single file pattern. Signet ring cells were also present. Cells were reactive with CK7, CK5/6, p63, GATA3, GCDFP-15 and Her 2-neu. Additional studies were negative, including TTF-1, CDX2, E-cadherin, mammaglobin, estrogen receptor and progesterone receptor. Thorough clinical and radiologic evaluation failed to identify an occult primary extracutaneous malignancy; however, regional lymphadenopathy, widespread osteoblastic lesions and multiple subcentimeter liver hypodensities were noted. Considering the clinical and histopathologic features, the diagnosis of primary cutaneous histiocytoid carcinoma with distant metastasis was favored.