Simulators of squamous cell carcinoma of the skin: diagnostic challenges on small biopsies and clinicopathological correlation.

Squamous cell carcinoma (SCC) is a common and important primary cutaneous malignancy. On skin biopsies, SCC is characterized by significant squamous cell atypia, abnormal keratinization, and invasive features. Diagnostic challenges may occasionally arise, especially in the setting of small punch biopsies or superficial shave biopsies, where only part of the lesion may be assessable by the pathologist. Benign mimics of SCC include pseudoepitheliomatous hyperplasia, eccrine squamous syringometaplasia, inverted follicular keratosis, and keratoacanthoma, while malignant mimics of SCC include basal cell carcinoma, melanoma, and metastatic carcinoma. The careful application of time-honored diagnostic criteria, close clinicopathological correlation and a selective request for a further, deeper, or wider biopsy remain the most useful strategies to clinch the correct diagnosis. This review aims to present the key differential diagnoses of SCC, to discuss common diagnostic pitfalls, and to recommend ways to deal with diagnostically challenging cases.

Tamoxifen-induced eccrine squamous syringometaplasia.

A 74-year-old woman had carcinoma of her right breast for which surgery was performed. Four weeks following the start of tamoxifen therapy, she developed papules and plaques over her face, trunk and limbs. A skin biopsy showed perivascular and periadnexal mixed inflammatory cellular infiltrate with fibroplasia. Notably, the dermis also showed squamous epithelial islands, which in foci were noted to be closely associated with eccrine epithelium. This was confirmed with double peroxidase - alkaline phosphatase immunohistochemistry - the eccrine lumina highlighted with carcinoembryonic antigen (polyclonal) and the squamous metaplasia positive for cytokeratin 5/6. Eccrine squamous syringometaplasia was diagnosed. With close clinicopathological correlation, the cutaneous eruption was attributed to tamoxifen. Following discontinuation of the drug, the eruption resolved. Eccrine squamous syringometaplasia has been reported to occur in association with diverse conditions, including skin ulcers, burns and as a cutaneous adverse drug reaction, most commonly to chemotherapeutic drugs. This is believed to be the first report involving tamoxifen.

Fibro-osseous pseudotumor of the digit: Presentation as an enlarging erythematous cutaneous nodule.

Fibro-osseous pseudotumor of the digit is an unusual ossifying fibro-proliferative lesion. The current case is a 54-year-old woman who presented with an enlarging reddish nodule on the distal aspect of her left big toe. Excision biopsy was performed and the histopathology featured a dermal-centered lesion composed of osteoblast-rimmed bony trabculae lying amidst fibrovascular stroma. This entity resembles and may be within the spectrum of myositis ossificans, the prototype post-traumatic reactive fibro-osseous proliferation, although the latter is typically more proximally located and features a zonation pattern on histopathology. The distinguishing features from other pathological differential diagnoses, such as subungual exostosis and extraskeletal osteosarcoma, are discussed. The growth is considered benign and local recurrence following complete excision is unusual.

Immunoexpression of Bcl-x in squamous cell carcinoma and keratoacanthoma: differences in pattern and correlation with pathobiology.

AIMS: Bcl-x is an important anti-apoptotic member of the Bcl-2 family. The aim was to determine its immunoexpression in cutaneous squamous cell carcinoma (SCC) and keratoacanthoma (KA). METHODS AND RESULTS: Sixteen SCCs and 39 KAs were investigated by Bcl-x immunohistochemistry. Bcl-x immunoreactivity was mostly diffuse in SCC (75% of cases), whereas that in KA was typically confined to the mid-to-upper spinous keratinocytes (95%) (P < 0.0001). There was a trend for SCC to have a higher likelihood of immunopositivity (weighted staining score > or =6 of 12) compared with KA (88% versus 59%, P = 0.058). Twenty-nine per cent of regressing KA had immunopositivity, whereas 47% and 82% of its stable and proliferating counterparts, respectively, had equivalent positivity (P = 0.024). CONCLUSIONS: These results provide some insight into the pathobiology of SCC and KA. The generally diffuse and stronger Bcl-x immunoreactivity in SCC suggests that the protein contributes to the survival advantage and aggressiveness of the tumour. In KA, the preferential reactivity of the mid-to-upper neoplastic keratinocytes can plausibly be explained by such differentiated cells attempting to prolong their existence under rapidly evolving circumstances, whereas the reduced reactivity in regressing KA is consistent with the end stage of the tumour.

Eosinophilic pustular folliculitis.

Classical eosinophilic pustular folliculitis, or Ofuji's disease, is a chronic and relapsing dermatosis that is predominantly reported in East Asian populations. Clinically, the disease typically begins as small papules, which enlarge and coalesce into a large plaque, usually on the face. The histopathology is characterized by a prominent eosinophilic infiltrate in the dermis with concentration around pilosebaceous units, often with eosinophilic microabscess formation. The differentiation of eosinophilic pustular folliculitis from other eosinophilic dermatoses is practically challenging and requires close clinicopathologic correlation. Eosinophilic pustular folliculitis may also be associated with human immunodeficiency virus infection, various drugs, and some lymphomas and could also be thought of as a nonspecific dermatopathologic pattern in such settings. The cause of classical eosinophilic pustular folliculitis is unknown, although immune processes are almost certain to play a key role in its pathogenesis.

Progressive macular hypomelanosis in Singapore: a clinico-pathological study.

INTRODUCTION: Progressive macular hypomelanosis (PMH), a condition of uncertain etiology, is characterized by asymptomatic hypopigmented macules predominantly located on the trunk. To date, there are no reports from South-East Asia concerning this condition. We sought to record the clinical features of PMH in Asian patients, identify etiologic factors, and study the structural and ultrastructural features of melanocytes in this disorder. METHODS: Patients who presented to the National Skin Center with acquired, hypopigmented macules on the trunk, without a history of inflammation or infection, were recruited. Erythrocyte sedimentation rate (ESR), complete blood count, fasting blood glucose, liver function tests, skin scrapings for fungi, and skin biopsy specimens (from lesional and normal skin) were obtained. Biopsies were stained with hematoxylin and eosin (H&E), Fontana Masson, an immunohistochemical panel for identification of melanocyte differentiation antibodies (HMB 45, Melan A, and S100) and CD 68. Electron microscopy (EM) was also performed. The patients were evaluated every 3 months. RESULTS: During a 9 month period, eight patients (all Chinese) presented with hypopigmented, ill-defined, confluent macules involving the lower aspect of the trunk. There were four men and four women, and the mean age was 25.9 years (range 19-45 years). Skin scrapings were negative for fungi and laboratory tests were normal. Microscopic evaluation of skin biopsy specimens showed reduced pigmentation of lesional as compared with normal appearing skin, but H&E-stained sections revealed only minimal histologic differences between lesional and normal skin. EM demonstrated a statistically significant (P = 0.047, Wilcoxon Signed Rank Test, Wilcoxon 95% CI 0.02-0.62) higher ratio of stage IV and late stage III (dark) melanosomes in normal vs. lesional skin. CONCLUSIONS: PMH may occur among young adults in Singapore. Its etiology is uncertain. The melanin content of lesional skin appears to be less than that in normal sites. EM shows a higher ratio of immature melanosomes in lesional vs. normal skin.

The myopathology of floppy and hypotonic infants in Singapore.

AIMS: This study attempts to determine the type and relative frequency of muscle diseases contributing to floppy and hypotonic infants in Singapore. METHODS: Eighty consecutive muscle biopsies in the Department of Pathology, National University of Singapore, in the period 1978-2000, in which a clinical diagnosis of floppy or hypotonic infant was made, were reviewed. RESULTS: The commonest cause of severe hypotonia in infancy was spinal muscular atrophy, which accounted for 33% of cases followed by congenital muscular dystrophy (13%). Eight cases (10%) of infantile type II glycogenosis (Pompe's disease) were encountered. There were seven cases of congenital myopathy, of which four were centronuclear myopathy, and one each of central core myopathy, nemaline myopathy and congenital fibre type disproportion. One case of centronuclear myopathy was associated with type I fibre smallness. Type II atrophy, which is generally considered a non-specific change, was encountered in five cases. Of interest is the relatively large number of muscle biopsies (29%) in which no significant pathological features were encountered at the light microscopic, histochemical as well as ultra-structural level. CONCLUSIONS: The study has revealed a great variety of pathology affecting the muscle of children presenting as floppy infants or with hypotonia. The muscle diseases included spinal muscular atrophy, congenital muscular dystrophies, congenital myopathies and metabolic myopathies. However, 23 (29%) cases showed no significant pathology. For this group of floppy and hypotonic infants further studies are needed.

Mite allergen induces allergic dermatitis with concomitant neurogenic inflammation in mouse.

Pathogenesis of atopic dermatitis involved the interactions of immune and neuroendocrine systems. Here we describe a mouse model for atopic dermatitis with concomitant neurogenic inflammation, by epicutaneous sensitization with a dust mite allergen. Allergen patching resulted in localized dermatitis characterized by pronounced epidermal hyperplasia and spongiosis, which was associated with infiltration of eosinophils and neutrophils, degranulated mast cells, CD4+ and CD8+ T cells, and dendritic cells. There was increased innervation of calcium gene related peptides and substance P in inflamed skins, interactions between nerve fibers and mast cells were seen, indicating the coexistence of neurogenic inflammation. Splenic T cells produced T helper 2-polarized cytokines in response to allergen stimulation in vitro, indicating systemic allergen sensitization. This is the first report of a mouse model of eczema, accompanied by neurogenic inflammation, which shows close resemblance to human allergic diseases. This work supports the notion that the skin is an important site for the initiation of primary allergen sensitization. Besides, this model may also be useful for study of other stress-associated neuroinflammatory skin disorders such as neurogenic pruritus and psoriasis.