Collision of Subungual Neurofibroma and Onychomatricoma: S100 Positivity as a Clue.

We present a 41-year-old man with a hemionychodystrophy of the first toe, appearing as a longitudinal thickening of the nail plate, overcurved and with holes in its thickened free margin, thus leading to the clinical diagnosis of onychomatricoma. Complete excision showed typical nail plate of onychomatricoma and, underlying it, curvy disorganized neural-looking fascicles without atypia and with diffuse positivity for S100, interpreted as subungual neurofibroma (NF). Subungual NF is a very rare tumor, with only 12 previous cases reported. Its diagnosis is based on histopathology, as the tumor presents waves or whorls of disorganized neural-looking cells positive for S100. Regarding onychomatricoma, it is characterized by typical glove finger digitations (which were present in our case) and an underlying stroma composed by a cellular superficial layer (this layer expresses CD34 but not CD99) and a more sclerotic and deeper area. As we did not find information on S100 expression in the stroma of onychomatricoma, we have stained 4 typical cases, and all were negative with S100 and positive with CD34, as expected. In conclusion, as "subungual NF" is so rare and, in our case, seems to collide with a typical onychomatricoma, we recommend adding S100 staining to properly characterize tumors involving nail plate, to detect underlying neural tumors, as has happened in our case.

Solid carcinoma is a variant of microcystic adnexal carcinoma: A 14-case series.

BACKGROUND: Solid carcinoma is a poorly characterized malignant apocrine neoplasm as only 16 cases have been published. OBJECTIVE: To characterize its clinical, histopathological, and immunohistochemical features. METHODS: We compiled 14 cases of solid carcinoma and clinical information were updated. Hematoxylin and eosin slides were reviewed and we stained all the cases for CEA, EMA, SMA, PHLDA-1, BerP4, nestin, p53, p63, p75, CK5/6, CK7 and some with remaining material for CK14, 15, CK10, CK19, S100, CD117, and CAM5. RESULTS: All the lesions were located on the scalp. Histopathologically, all the cases were characterized by solid aggregates of neoplastic epithelial cells without nuclear atypia or mitotic figures involving all the dermis. All the cases presented perineural infiltration and most of them had cornified cystic structures. CK5/6 and p63 were positive. CEA and EMA underlined the scarce ducts. Ki67 was lower than 1%. BerEP4 and PHLDA-1 were negative. CONCLUSION: Solid carcinoma is a solid variant of MAC affecting the scalp more frequently than classic MAC, mostly in old males and showing variable-sized nests involving the entire dermis and composed by poroid, clear-cells, or a mixture of both. It is positive for p63 and CK5/6 and negative for BerEP4 and PHLDA-1. Staining features with CK19 and PHLDA1 differ from classic MAC.

Late-Stage Erythema Elevatum Diutinum Mimicking a Fibroblastic Tumor: A Potential Pitfall.

Erythema elevatum diutinum (EED) is a rare dermatosis with evolving histopathological features that vary according to the age of the lesions, with a variable fibrosis and a fascicled proliferation of spindle cells in late phases. The authors present an otherwise healthy 57-year-old woman with multiple indurated nodules on the inner aspect of both feet. Skin biopsy showed storiform interlacing bundles of spindled cells with plump nuclei and some areas with neutrophils and leukocytoclasia. CD34 and S100 were negative. This case is noteworthy clinically due to its location and its histopathological presentation that comprises a wide differential diagnosis, including inflammatory pseudotumor, dermatofibrosarcoma protuberans, superficial nodular fasciitis, hyalinized leiomyoma, sclerosing spindle cell perineuroma, and sclerotic fibroma. The authors have reviewed the main histopathological and immunohistochemical features that help in the differential diagnosis of this rare variant of EED. A careful search for leukocytoclasia and neutrophilic vasculitis is mandatory to establish the right diagnosis of nodular or late-stage EED and avoid the pitfall of considering this a neoplastic process.

Clues in Histopathological Diagnosis of Panniculitis.

BACKGROUND: Panniculitides comprise a group of heterogeneous inflammatory diseases. Nevertheless, histopathological study along with clinicopathological correlation usually led to a specific diagnosis. In most textbooks, the first step in the diagnosis is to classify them as mostly septal or lobular depending on where the inflammatory infiltrate is located. The second step is deciding if vasculitis is present or not. Finally, the third step is further characterizing the inflammatory infiltrate. However, in addition to the algorithmic approach to panniculitis diagnosis, some subtle changes may help to the diagnosis. OBJECTIVE: To review some clues in panniculitis dermatopathological diagnosis such as presence of granulation tissue, sclerotic connective tissue septa, small granulomas arranged around a central clear space, so-called ghost adipocytes, needle-shaped crystals, small lobules with a proliferation of capillaries, Splendore-Hoeppli phenomenon, refractile microspheres, neutrophilic infiltrates, granulomas and fibroplasia or presence of adipose tissue in dermis. METHODS: We have compiled 12 clues based in our personal experience in this field. LIMITATIONS: Specificity and sensibility of every clue may vary and these clues are a guide to correct diagnoses that should rely in clinicopathological correlation. CONCLUSION: Knowledge of these 12 clues will help to increase the diagnostic accuracy in panniculitis diagnosis.

Histopathologic clues for the diagnosis of Wiesner nevus.

The dermatologic hallmark of a recently described BAP1-associated cancer susceptibility syndrome is a dome-shaped nevus with distinct clinicopathological features, first delineated by Wiesner and colleagues. Here we describe the leading histopathological criteria of Wiesner nevus. Wiesner nevus is composed of various nevomelanocytic populations all showing different degrees of atypia ranging from hyperchromatic nevus cell-like to large atypical epithelioid cells. Immunohistochemically, Wiesner nevus is BAP1 negative and VE1 positive.

Granulomatous variant of pigmented purpuric dermatosis.

Granulomatous pigmented purpuric dermatosis is a rare entity. Historically, it has been seen in Asians. In this article, we report the case of a white man with this unusual variant. A 65-year-old, white man presented with a 1-year history of asymptomatic purpuric to brown papules on both lower legs and more confluent on dorsum of feet. He had an underlying history of hypertension and hyperlipidemia. Skin biopsy revealed a granulomatous lympho-histocytary inflammatory infiltrate in papillary dermis and superficial reticular dermis with extravasation of red blood cells and siderophages. Periodic acid schiff (PAS), Giemsa and Ziehl-Neelsen stains were negative. A diagnosis of granulomatous pigmented purpuric dermatosis was made. From the 10 cases reported of this granulomatous variant, 6 were associated with hyperlipidemia. We report an additional case with this association.