Michael Sidiropoulos

γδ T-cell-rich variants of pityriasis lichenoides and lymphomatoid papulosis: benign cutaneous disorders to be distinguished from aggressive cutaneous γδ T-cell lymphomas

T cells with a γδ phenotype have been associated with aggressive lymphomas. Yet, inflammatory skin disorders and low‐grade lymphoproliferative disorders have rarely been described with a predominant γδ T‐cell infiltrate.

Superficial paramucosal clear cell sarcoma of the soft parts resembling melanoma in a 13‐year‐old boy

Clear cell sarcoma (CCS) of tendons and aponeuroses, also known as melanoma of soft parts, represents an aggressive rare malignancy that is characterized by a nested or fascicular pattern of spindled cells and a pathognomonic reciprocal translocation, t(12;22)(q13;q12), that results in the fusion of EWSR1 and ATF1 genes. Numerous recent studies have recognized the importance of a cutaneous CCS variant that can mimic a broad spectrum of entities, including spindle cell melanoma, spindle cell squamous carcinoma, cutaneous leiomyosarcoma and atypical fibroxanthoma. We report a case of a 13‐year‐old boy with cutaneous CCS who presented with a few months history of an asymptomatic papule on the lower lip that was suggestive of a mucocele. Biopsy of the lesion showed a wedge shaped neoplasm arranged in nests and fascicles of epithelioid‐ to oval‐shaped cells with pale cytoplasm, open chromatin and prominent nucleolus. The superficial component was closely opposed to the basal epithelium resembling the junctional nests of a melanocytic neoplasm. The process extended into and involved the striated muscle of the lip. The cells expressed S‐100, CD99 and synaptophysin by immunohistochemistry, and there was focal HMB‐45 and microphthalmia transcription factor (MiTF) positivity as well. Fluorescence in situ hybridization confirmed the presence of the t(12;22) (ESWR1‐ATF1) translocation.

Desmoplastic nevus of chronically sun-damaged skin: an entity to be distinguished from desmoplastic melanoma.

Abstract:Desmoplastic (sclerotic) nevus (DSN) can often be difficult to differentiate from desmoplastic melanoma (DM). This can be especially difficult when DSNs occur in a background of heavy solar elastosis. We have observed numerous examples of DSNs occurring in chronically sun-damaged (CSD) skin. In a subset of these cases, we have observed notable pleomorphism and nuclear atypia raising concern for the possibility of DM. In this study, we evaluated the clinical, histopathologic, and immunohistochemical findings in 23 cases of DSN occurring in CSD skin and compared them with 10 cases of DM. DSN on CSD skin is seen in adults (mean, 53.2 years) with a female predominance (70%) and upper (57%) and lower (17%) extremity anatomic locations. Most DSNs present as small flesh-colored macules or papules. Typical histologic features include symmetry, limited junctional growth, presence of a lentiginous component often with focal and limited pagetoid spread (extension across only a few rete ridges), and lack of deep extension. DSN and DM had a statistically significant difference in immunohistochemical staining for Melan-A and p75. Melan-A was positive in 18 of 20 DSNs and only 2 out of 10 DMs, whereas p75 was positive in all DMs (10/10) and was weakly positive in 11 of 20 DSN cases. We believe that our study offers some useful clinical, histologic, and immunohistochemical clues to help differentiate DSNs on CSD skin from DMs.

Chronic actinic dermatitis/actinic reticuloid: A clinicopathologic and immunohistochemical analysis of 37 cases

Abstract:Chronic actinic dermatitis/actinic reticuloid (CAD/AR) is an eczematous hypersensitivity reaction to ultraviolet rays that can vary from mild eczematous cases to AR, the most severe cases which may resemble cutaneous T-cell lymphoma. Diagnosis is based on clinical, histopathologic, and photobiologic features. In this study, we characterize the histopathologic and immunohistochemical features of 40 biopsies from 37 patients with established CAD. The cohort included 30 men and 7 women, ranging in age from 38 to 84 years (median, 62 years) and with a median duration of symptoms at presentation of 3 years (range, 1 to 40 years). All patients presented with erythematous lichenified plaques on sun-exposed areas. Severe cases (12/37) had extension to non-exposed areas. Positive photo-testing (20/20) and patch-testing (10/10) results, and cases with a high peripheral blood eosinophila (7/24) and HIV positivity (4/37) were noted. Skin biopsies demonstrated eczematous features including parakeratosis, acanthosis, spongiosis, and prominent dermal fibroplasia. Dermal dendrocytes were prominent in all cases with frequent multinucleated giant cells positive for factor XIIIa and S100 protein. Most cases displayed a brisk lymphocytic infiltrate with subtle exocytosis, atypical lymphocytes, and increased numbers of Langerhans cells, eosinophils, and plasma cells. There was a predominance of CD8 T cells within the epidermis (20/25) and a low CD4:CD8 ratio was noted in 20 of 25 cases. T-cell clonality studies were negative in 10 of 10 cases. CAD/AR may be difficult to distinguish from eczematous variants of cutaneous T-cell lymphoma. Important clues to differentiate both conditions include the identification of prominent dermal dendrocytes with multinucleated giant cells, eosinophils, plasma cells, and a low CD4:CD8 ratio.

Angiomyxoma of the nasal dorsum treated by Mohs surgery

Cutaneous angiomyxomas are myofibroblastic neoplasms with locally aggressive behaviour and a high risk of recurrence. We describe a case of a solitary cutaneous angiomyxoma presenting on the nasal dorsum of a 28‐year‐old man, excised with Mohs surgery using permanent section control and repaired with an advancement flap. Histology showed myxoid nests of bland CD34‐positive and vimentin‐positive stellate and spindled cells in the deep dermis and abundant thin‐walled blood vessels. An echocardiogram, performed to rule out the possibility of a cardiac myxoma with cutaneous embolisation, was normal.

Focal cutaneous mucinosis after knee replacement: A rare entity successfully treated with intralesional polidocanol

Cutaneous focal mucinosis is a heterogeneous disorder characterized by abnormal deposition of mucin within the skin. It can be primary (idiopathic) or secondary (associated with a neoplasm or inflammation).1 Mucin is an amorphous, gelatinous substance important for the homeostasis of ground substance and joint fluid. It consists of hyaluronic acid and is usually produced by fibroblasts or synovial cells. Resorption of intra-articular fluid typically occurs through uptake by blood vessels, lymphatics, and perineural spaces.2 There is a paucity of published cases of cutaneous mucinosis developing adjacent to replaced joints.3, 4 Apart from presenting our patient, we review the literature, propose the pathogenesis, and suggest treatment for this unusual cutaneous presentation.

Apocrine Hidrocystoma of the Urethral Meatus: A Case Report

This is a copy of an article published in the Acta dermato-venereologica

A Tumor on the Leg of a 2-Year-Old Girl

A 6-year-old girl presented with a 6-month history of two nodules on her right cheek. Her medical history was significant for a choledochal cyst that had been treated with surgical excision when she was 2 years old with no significant long-term sequelae. Physical examination revealed two nontender, firm nodules on her right cheek with a violaceous hue but otherwise no overlying surface change (Fig. 1). She also had several pink papules on her cheeks and chin. A punch biopsy was performed on one of the nodules (Fig. 2).

Fluorescence in Situ Hybridization (FISH) Copy Number Abnormalities at 6p (RREB1), 6q (MYB), and 11q (CCND1) Reliably Distinguish Metastatic Versus Benign Melanocytic Lesions

Objectives: Malignant melanoma can be difficult to distinguish from a benign melanocytic lesion by histology. In this study, we investigated the sensitivity and specificity of FISH to distinguish between benign nevi and metastatic melanomas to lymph nodes. Methods: Multicolour FISH was performed using a commercially available probeset (Abbott Laboratories, Abbott Park, IL), on formalin-fixed, paraffin-embedded tissue samples from 40 tumours: 20 benign melanocytic nevi, and 20 metastatic melanomas within lymph nodes, as determined by histologic assessment. Fluorescent signals for each probe were enumerated by 2 observers in 30 cells each per lesion. An algorithm using signal counts from a combination of 4 probes targeting chromosome 6p25 (containing RREB1 gene), 6 centromere (CEP6), 6q23 (containing MYB gene), and 11q13 (containing CCND1 gene) was used as suggested by the manufacturer. Results: Of the 20 metastatic melanomas assessed, 18 were FISH positive. FISH detected significant abnormal nuclei for RREB1 in 17/20 cases (85%) and significant MYB loss in 12/20 cases (60%). Average signals per nuclei greater than 2.5 for CCND1 and MYB were present in only 7/20 (35%) and 4/20 (20%) cases respectively. All 20 benign nevi were FISH negative. Overall, the FISH test showed a sensitivity of 90% and specificity of 100% in the diagnosis of metastatic melanoma in lymph nodes. Conclusions: These results provide further compelling evidence for the utility of multicolour FISH directed against 6p25 (RREB1), centromere 6, 6q23 (MYB), and 11q13 (CCND1) as an aid in determining malignant behavior in melanocytic lesions.