Primary cutaneous Ewing's family sarcoma. Report of a case with immunostaining for glycoprotein p30/32 mic2.

The differential diagnosis of cutaneous small round cell malignancies is a relatively uncommon but recurrent problem that usually requires adjuvant techniques including special histochemical stains, immunohistochemistry (IHC), electron microscopy (EM), and cytogenetics (CG) to arrive at a definite answer. This report describes a case of a primary cutaneous malignancy that, after workup, fulfilled the criteria of extraskeletal Ewing's family sarcoma, which was corroborated by IHC with an antibody to glycoprotein p30/32 mic2 that is highly expressed in these neoplasms. The lesions consisted of a large nodular proliferation of poorly differentiated monotonous small round cells confined to the dermis and subcutaneous tissue. The cells had high nuclear to cytoplasmic (N/C) ratios, scattered prominent nucleoli, and indistinct cytoplasm. A periodic acid-Schiff (PAS) stain with and without diastase demonstrated abundant cytoplasmic glycogen. The glycogen was confirmed with EM, which did not show neurosecretory granules, but extensive sectioning of the tissue blocks demonstrated with light microscopy a single focus with pseudorosette formation. IHC was positive for monoclonal antibody (MAb) O13 to glycoprotein p30/32 mic2 and negative for lymphoid (CD45), neural (S-100, NF, GFAP), neuroendocrine (NSE), and muscle (MSA, desmin) markers. To the best of our knowledge, this is one of few reported cases of primary cutaneous (extraskeletal/extraosseous) Ewing's sarcoma (EEWS) and the first to use IHC with MAb O13, which recognizes the cell surface glycoprotein p30/32 mic2. This case further illustrates the continuum between EEWS and primitive peripheral neuroepithelioma and supports the unifying concept that these two entities are merely subtle morphologic variants of the same malignant neoplasm, which is better designated a Ewing's family sarcoma.

Mollaret's meningitis: case report with immunocytochemical and polymerase chain reaction amplification studies.

Mollaret's meningitis is a rare disease with a characteristic clinical course and distinctive cerebrospinal fluid (CSF) cytology. Although Mollaret originally described the large mononuclear cells seen in the CSF as endothelial, subsequent ultrastructural and immunocytochemical studies support a monocyte/macrophage lineage for these cells. To data, the pathogenesis of this entity remains uncertain, although an association with herpes simplex virus (HSV) has been reported in rare cases. In the current case study, immunocytochemistry for factor VIII-related antigen, leukocyte common antigen, and macrophage-specific antigen were performed and provide additional evidence of a monocyte/macrophage lineage for Mollaret cells. Polymerase chain reaction amplification for HSV DNA was done to further explore one possible etiology for this disease, but was negative.

Chondrosarcomatous cutaneous metastasis. A unique manifestation of sarcomatoid (metaplastic) breast carcinoma.

Breast carcinoma is the most common origin of cutaneous metastasis in women but is usually of ductal or lobular histotypes. Sarcomatoid (metaplastic) carcinoma of the breast, although a well-established aggressive neoplasm, is very uncommon. The metaplastic elements span all types of mesenchymal differentiation and have been demonstrated to be derived from carcinomatous elements. Skin metastasis from such lesions is extremely rare. A case of metastatic sarcomatoid breast carcinoma to the skin is described in which the histology of the metastases was that of chondrosarcoma.

Recurrent pigmented melanocytic nevus. A benign lesion, not to be mistaken for malignant melanoma.

Melanocytic nevi that recur after incomplete removal are pigmented lesions that may clinically and pathologically simulate malignant melanoma in situ. Five examples of recurrent pigmented melanocytic nevus, with emphasis on light microscopic and immunohistochemical findings, are reported herein. Prominent HMB-45 staining in these nevi may cause further confusion in differentiating them from malignant melanoma. The differential diagnosis of recurrent pigmented melanocytic nevi is discussed, with particular emphasis on distinguishing these lesions from malignant melanoma. Our immunohistochemical observations indicate that the recurrences most likely develop as a result of proliferation of melanocytes remaining in the epidermis and/or adnexae following incomplete removal. The approach and management of recurrent nevi are also discussed.