Antoinette B. Thomas

Myeloid leukemia cutis: a histologic and immunohistochemical review.

Background:  The histologic diagnosis of myeloid leukemia cutis (LC) can be difficult, requiring confirmatory immunohistochemical stains.

Utility of p63 in the differential diagnosis of atypical fibroxanthoma and spindle cell squamous cell carcinoma

Atypical fibroxanthoma (AFX), spindle cell squamous cell carcinoma (SCSCC) and spindle cell melanoma are the primary entities in the differential diagnosis of a cytologically atypical spindle cell tumor arising on sun‐damaged skin. AFX is generally regarded as a diagnosis of exclusion in this context: in the absence of S100 or keratin reactivity, a diagnosis of AFX is favored. However, keratin reactivity may be focal or even absent in SCSCC, and although numerous positive markers of AFX have been proposed, none has shown sufficient sensitivity and specificity for routine diagnostic use. We evaluated 20 AFX and 10 SCSCC with a panel of cytokeratins and p63 to assess the utility of the latter antibody in this differential diagnosis. All 10 SCSCC showed strong expression of p63, whereas all 20 AFX were p63 negative. Two additional cases (excluded from the study) were negative for keratins and S100 on initial shave biopsies, resulting in a favored diagnosis of AFX, but p63 stains performed retrospectively were positive. However, review of the excision specimens in both cases revealed deep subcutaneous extension, excluding AFX. p63 reactivity argues against the diagnosis of AFX and is therefore a useful addition to the standard immunohistochemical panel for cutaneous spindle cell neoplasms.

Expression of MiTF may be helpful in differentiating cellular neurothekeoma from plexiform fibrohistiocytic tumor (histiocytoid predominant) in a partial biopsy specimen.

Background Overlapping histopathologic features of cellular neurothekeoma (CNT) and plexiform fibrohistiocytic tumor (PFHT), when both are predominantly composed of histiocytoid cells, make distinction between these entities challenging. Some have suggested that CNT and PFHT are related entities. No prior study has demonstrated a reliable immunohistochemical panel to differentiate these entities. Methods Skin biopsies diagnosed as CNT and PFHT, from 2004 to 2010 were retrieved with accompanying pathology reports. Each case was reviewed by at least 2 dermatopathologists and 2 soft tissue pathologists for confirmation of diagnosis. All cases were then evaluated for immunohistochemical expression of PAX2, NKIC3, CD10, and microphthalmia transcription factor (MiTF). Results Histopathologically, the histiocytoid areas of each tumor shared similar architecture, demonstrating nests and fascicles of histiocytoid to spindled cells, with some separation of nests by collagen bands. Both CNT and PFHT were uniformly positive for NKIC3 and CD10, and both were frequently PAX2 positive. MiTF was strongly and diffusely positive in CNT and was consistently negative in the PFHT. Conclusions CNT and PFHT share many histopathologic features and immunohistochemical staining patterns. Of the stains we evaluated, we found that expression of MiTF may be a reliable marker for distinguishing CNT from histiocytoid-predominant PFHT, especially in instances where only a small part of the tumor is sampled for evaluation.

Sebaceous carcinoma of the nipple.

Sebaceous carcinoma (SC) is an uncommon neoplasm that usually presents as an ocular or extraocular cutaneous lesion of the head and neck. We report a case of an 83‐year‐old woman with SC of the nipple. To our knowledge, this is the first report of SC arising in the nipple.

Extra-acral cutaneous/soft tissue sclerosing perineurioma: an under-recognized entity in the differential of CD34-positive cutaneous neoplasms.

Background: Perineuriomas are an uncommon group of tumors composed of perineurial cells of peripheral nerve sheath lineage. Variants include soft tissue (extraneural), intraneural, sclerosing, reticular and plexiform forms. Sclerosing perineuriomas have been reported to occur almost exclusively on the hands of young men. Herein, we report three extra‐acral cutaneous/soft tissue perineuriomas that show significant associated sclerosis.

Sarcomatoid renal cell carcinoma presenting in the oropharynx

Metastasis stemming from a distant malignancy is far less common than an oropharyngeal primary and represents only 1% of all oral neoplasms. The difficulty in diagnosing a metastasis in the oropharynx may be compounded if the lesion is poorly differentiated and bears little resemblance to the primary tumor. We present the case of synchronous metastatic renal cell carcinoma of the mandibular gingiva in a woman with sarcomatoid clear cell renal cell carcinoma. The metastatic lesion was poorly differentiated and lacked expression of the renal cell carcinoma (RCC) antigen. In contrast, PAX‐8 staining was strongly positive. This case serves to highlight the diagnostic difficulty posed by poorly differentiated lesions in the oropharynx and reinforces the sensitivity of the cell lineage‐specific transcription factor PAX‐8 in poorly differentiated RCC.

Cellular neurothekeoma with fascicular growth features mimicking cellular dermatofibroma.

Background:Cellular neurothekeoma (CNT) is a benign cutaneous mesenchymal neoplasm. Most demonstrate a lobulated to micronodular architecture. Rarely, CNT demonstrates a predominantly fascicular growth pattern, without prominent sclerosis and thus can mimic cellular dermatofibroma (DF). Methods:Three CNT with a predominantly fascicular pattern were obtained. The clinicopathologic features and accompanying immunohistochemical stains were evaluated. Results:All cases demonstrated a moderately cellular proliferation of epithelioid to spindle cells with pale to eosinophilic slightly granular cytoplasm, vesicular nuclei, and a single nucleolus arranged in a fascicular pattern with thick collagen bundles at the periphery (collagen trapping). One case had prominent epidermal hyperplasia. The neoplastic cells expressed NKI-C3, CD10, and micropthalmia transcription factor and lacked expression of factor XIIIa, S-100, epithelial membrane antigen, and CD34. Conclusions:Our cases showed an unusual pattern of CNT with a predominantly fascicular growth pattern, thickened collagen bundles at the periphery, and occasionally epidermal hyperplasia. The overlap with cellular DF is striking. The presence of plump to epithelioid cytomorphology with abundant cytoplasm, with focally prominent nucleoli; the presence of focal lobulated to micronodular growth pattern along with micropthalmia transcription factor positivity; and lack of factor XIIIa expression are helpful in distinguishing fascicular CNT from cellular DFs.

Clinicopathologic findings in (anti‐FcepsilonR1alpha) autoimmune‐related chronic urticaria

One cause of chronic urticaria is autoreactivity which is diagnosed by detecting autoantibodies against the IgE receptor alpha subunit (anti‐Fc R1alpha).

An audit of dermatopathology requisitions: hand written vs. electronic medical record data entry accuracy

At our institution, dermatopathology case requisitions are received in hand written form or via electronic medical record (EMR). Categories for requisition data entry include patient demographics, physician name and procedure site/date. Systematic data entry problems potentially cause considerable documentation error, propagate inaccurate patient information and potentially delay billing/revenue collection.

Cutaneous meningioma: a potential diagnostic pitfall in p63 positive cutaneous neoplasms

Cutaneous meningiomas are divided into three groups. Type I lesions present at birth and are derived from ectopic arachnoid cells. Type II lesions usually present in adults and are derived from arachnoid cells surrounding nerve bundles. Type III lesions are due to direct extension or metastasis from dural‐based neoplasms. Dural‐based meningiomas are known to express p63. The aim of our study is to examine the expression of p63 in type II and type III meningioma. Two cases of cutaneous meningioma (type II and type III) were evaluated for the expression of p63, EMA, CK 5/6, S100 and CD31. The cells of interest were spindled to epithelioid and arranged in a whorling pattern. Immunohistochemical staining showed expression of EMA and p63 in both cases, while stains for CK 5/6, S100 and CD31 were negative. Among cutaneous tumors, p63 is considered a marker of epithelial derivation, as it is positive in epidermal and adnexal neoplasms. It is important to be aware of p63 expression in the context of cutaneous meningioma to avoid misinterpretation as an epithelial tumor. On the basis of our small study, it is unlikely that p63 expression would be helpful in distinguishing between type II and type III meningioma, as both may be p63‐positive.