Proliferation and differentiation of the keratinocytes in hyperplastic epidermis overlying dermatofibroma: immunohistochemical characterization

Histologic Mimics of Basal Cell Carcinoma

CONTEXT

- Basal cell carcinoma (BCC) is the most common human malignant neoplasm and is a frequently encountered diagnosis in dermatopathology. Although BCC may be locally destructive, it rarely metastasizes. Many diagnostic entities display morphologic and immunophenotypic overlap with BCC, including nonneoplastic processes, such as follicular induction over dermatofibroma; benign follicular tumors, such as trichoblastoma, trichoepithelioma, or basaloid follicular hamartoma; and malignant tumors, such as sebaceous carcinoma or Merkel cell carcinoma. Thus, misdiagnosis has significant potential to result in overtreatment or undertreatment.

OBJECTIVE

- To review key features distinguishing BCC from histologic mimics, including current evidence regarding immunohistochemical markers useful for that distinction.

DATA SOURCES

- Review of pertinent literature on BCC immunohistochemistry and differential diagnosis.

CONCLUSIONS

- In most cases, BCC can be reliably diagnosed by histopathologic features. Immunohistochemistry may provide useful ancillary data in certain cases. Awareness of potential mimics is critical to avoid misdiagnosis and resulting inappropriate management.

Primitive follicular induction in molluscum contagiosum

BACKGROUND

Molluscum contagiosum (MC) is the commonest human poxvirus infection. Follicular induction has rarely been observed in the epidermis surrounding lesions of MC. A virus-induced localized proliferation of germinative/stem cells of the folliculosebaceous-apocrine unit has been suggested as the underlying cause, however few reports of this peculiar phenomenon exist in the literature and the mechanisms involved in this proliferation require further study.

METHODS

We prospectively collected MC cases showing multifocal areas of primitive follicular induction involving the adjacent undersurface epidermis. Immunohistochemical expression of BerEP4, PHLDA1 and cytokeratin 20 (CK20) was evaluated in the basaloid germs surrounding the lesions. For PHLDA1, we used epidermal melanocytes as a positive internal control. For BerEP4, we employed a basal cell carcinoma (BCC) and for CK20, colon as positive external controls. An incubation without the primary antibody functioned as an external negative control.

RESULTS

All the cases studied showed an intense positive staining of the basaloid buds with BerEP4 and weaker stain for PHLDA1. CK20 showed the presence of scattered Merkel cells within the induced epidermal basaloid proliferations favoring their reactive origin.

DISCUSSION

The pathogenetic mechanisms behind the development of these microscopic features and the link between follicular induction and poxvirus infection are explored. Awareness of this unusual phenomenon by dermatopathologists will be helpful in avoiding a misdiagnosis of a superficial BCC in such cases.

CONCLUSIONS

BerEP4 and PHLDA1 were consistently expressed in the areas of primitive follicular induction surrounding lesions of MC. CK 20 stained the Merkel cells present in the basaloid buds. All these findings support the reactive origin of this phenomenon, which we believe is most probably viral-induced.

Sebaceous induction in dermatofibroma: a common feature of dermatofibromas on the shoulder

BACKGROUND

Dermatofibroma (DF) has multiple histopathological variants and overlying acanthosis, hyperkeratosis and hyperpigmentation are often present. We have frequently observed sebaceous induction in DFs on the shoulder and wanted to assess if this is a site-specific finding.

METHODS

We prospectively collected 100 DFs and assessed for sebaceous induction, the histopathologic pattern of the DF and any associated-epidermal changes. We retrospectively searched for DFs with sebaceous induction to assess the anatomic site of the biopsy.

RESULTS

In the 100 prospectively collected DFs, 49% occurred on the lower extremities, 39% on the upper extremities, 10% on the trunk and 2% on the head. Sebaceous induction was present in 16 DFs, 81% of which occurred on or near the shoulder. The most common variant was fibrocollagenous DF (64%), including in DFs with sebaceous induction. The retrospective search for DFs with sebaceous induction found 19 cases in which 95% occurred on the shoulder area. Sclerotic pattern DFs were most common in this retrospective cohort (47%), and seborrheic keratosis-like hyperplasia occurred in 100% of these cases.

CONCLUSION

DFs occurring on the shoulder have a high incidence of sebaceous induction with seborrheic keratosis-like epidermal hyperplasia and a fibrocollagenous or sclerotic pattern.

The involvement of fibroblast growth factor receptor signaling pathways in dermatofibroma and dermatofibrosarcoma protuberans

Fibroblast growth factors (FGFs) and their receptors (FGFRs) control a wide range of biological functions; however, their involvement in the pathogenesis of dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) is currently unknown. In this study, we first confirmed the histological diagnosis by detecting fusion COL1A1-PDGFB transcripts in DFSP, and examined the expression of all FGFRs (FGFR1-4), some of their ligands (FGF1, 2, 9), and forkhead box N1 (FOXN1) as a downstream target of FGFR3 in DF and DFSP by immunohistochemical analysis. Although we failed to detect the expression of FGF1 and FGF9 as specific ligands for FGFR3 in DF, overexpression of FGFR3 and FOXN1 was observed in the epidermal regions of DF, suggesting that the epidermal regions of DF were similar to seborrhoeic keratosis both in terms of histological features and the activation of FGFR3/FOXN1. In addition, strong expression of FGF2 and FGFR4 was observed in the tumor lesions of DF. Expression patterns of FGFR3/FOXN1 and FGF2/FGFR4 in DF were in contrast with those of DFSP. The activation of FGFR signaling pathways may be not only relevant to the pathogenesis of DF, but also very useful in the differential diagnosis of DF and DFSP.

Follicular induction overlying a dermatofibrosarcoma protuberans

The term "induction" has been used to describe epidermal changes overlying a dermatofibroma (DF). Follicular induction is most often associated with DF, but can be observed in other lesions, including focal mucinosis, nevus sebaceous, seborrheic keratosis, wart, neurofibroma, and scars. Dermatofibrosarcoma protuberans (DFSP) is a malignant fibrohistiocytic tumor that may be difficult to distinguish from DF. In contrast to DF, the epidermis overlying DFSP is usually attenuated or ulcerated. Here, we report a case of DFSP exhibiting follicular induction of the overlying epidermis. This epidermal change has been rarely reported in DFSP and may present a diagnostic pitfall in superficially sampled lesions.

[Folliculosebaceous cystic hamartoma: anatomo-clinical study]

BACKGROUND

Folliculosebaceous cystic hamartoma (FSCH) is a relatively recently described malformation with follicular and sebaceous components and a particular type of stroma with adipocytes. We conducted an anatomo-clinical study in order to clarify the clinical and histological characteristics of FSCH.

MATERIALS AND METHODS

We included all cases of FSCH diagnosed between 1985 and February 2011 at our dermatopathology laboratory. Clinical information was obtained from medical records and requests for histological examination.

RESULTS

We studied 25 cases of FSCH in 25 patients of mean age 51 years. The sex ratio was 1.3. The mean disease duration was 9 years. Lesions were described mainly as flesh-colored, occasionally pedunculated nodules and were found primarily on the face (60%). The diagnosis of FSCH had never been mentioned by the clinician. Histological examination revealed in all cases one or more follicular cystic structures surrounded by sebaceous glands in a stroma containing adipocytes. A number of variants were identified, such as the presence of a mucinous stroma, a neuroid component with protein S 100 expression, and rudimentary hair follicles in adjacent dermis. One case involved a proliferating cyst while another was on the scalp in the area of pre-existing radiodermatitis. Only one relapse was noted, 5 years after the initial excision.

DISCUSSION

FSCH is a benign, underdiagnosed lesion, localized on the face, particularly on the nose. It is dome-shaped or pedunculated and grows slowly. Differential diagnoses include nevus lipomatosus superficialis and "sebaceous" trichofolliculoma. FSCH can be readily identified by the presence of adipocytes and a fibrous stroma. One case was unique in its appearance of a large pedunculated nodule with a proliferating cyst. Prior to the invidualization of this entity, such cases were interpreted as nevus lipomatosus superficialis or "sebaceous" trichofolliculoma, although their histological appearance was inconsistent with such a diagnosis.

The man behind the eponym: Hans Biberstein and follicular hyperplasia overlying dermatofibroma

Hans Biberstein first described the basaloid follicular hyperplasia overlying dermatofibromas in 1923 and published his extensive observations on the subject in 1931. Part of Josef Jadassohn's department in Breslau, he was forced to leave German by the National Socialist regime and spent the rest of his career in New York. After a hiatus of 30 years, the dermatopathologic literature once again began addressing his seminal finding but never gave him proper credit. We suggest Biberstein's sign as an appropriate term for basaloid follicular hyperplasia overlying a dermatofibroma and as a small tribute to a pioneer dermatopathologist.

Dermatofibroma: a possible model of local fibrosis with epithelial/mesenchymal cell interaction

Dermatofibromas are benign dermal nodules usually seen on the extremities; however, whether a dermatofibroma is a reactive fibrous hyperplasia or a true neoplasm is still unclear. Fibrous type dermatofibromas might be regarded as the symptom of local fibrotic processes and thus present a possible model of local fibrosis. Interaction between proliferated dermatofibroma fibroblasts and overlying elongated epidermis suggests a relationship between keratinocytes and mesenchymal cells. We herein describe current insights into the pathogenesis of dermatofibromas and explore the possible involvement of immunocytes around fibroblasts and effector cells which play an important role in the development of dermatofibromas.

Cutaneous focal mucinosis causing follicular induction of the epidermis

Cutaneous focal mucinosis has been rarely reported in association with follicular induction of the epidermis. We present 2 cases of focal mucinosis with follicular induction and describe the histopathologic findings to create awareness of this association and to prevent confusion with other diagnoses such as dermatofibroma with follicular induction or superficial basal cell carcinoma.

Phenotypic characterization of human keratinocytes in coculture reveals differential effects of fibroblasts from benign fibrous histiocytoma (dermatofibroma) as compared to cells from its malignant form and to normal fibroblasts

BACKGROUND

Benign and malignant fibrous histiocytoma present with a considerable difference concerning cellular organization in their vicinity.

OBJECTIVE

Normally appearing epithelium covers the malignant form in contrast to hyperplastic epidermis for benign tumors. It is an open question as to whether the tumor-associated fibroblasts are capable to affect phenotypic features of normal keratinocytes, prompting this comparative analysis.

METHODS

Fibroblasts were isolated from benign and malignant fibrous histiocytomas, respectively, and also from normal dermis. The resulting cell populations were thoroughly characterized immunocytochemically using a large panel of antibodies. The three fibroblast preparations were cocultured with normal interfollicular keratinocytes. Their phenotype was characterized for distinct properties including differentiation and proliferation.

RESULTS

Fibroblasts prepared from both tumor types were phenotypically practically identical with normal dermal fibroblasts. Their activities on keratinocytes were different. Cells prepared from benign fibrous histiocytoma were capable to effect strong expression of keratin 19 and production of a galectin-1-rich extracellular matrix. Fibroblasts isolated from malignant fibrous histiocytoma led to a phenotype very similar to that when keratinocytes were cocultured with normal dermal fibroblasts.

CONCLUSION

Fibroblasts prepared from benign fibrous histiocytoma were biologically active on keratinocytes in a particular manner. Our results on fibroblast activity are suggested to be relevant for morphologic differences observed in vivo between normal epidermis and epidermis adjacent to the studied tumor types.

Melanoma associated with a dermatofibroma

BACKGROUND

Dermatofibromas are common benign cutaneous fibrohistiocytic neoplasms, whereas melanomas are potentially aggressive malignancies. Differentiating these two entities can occasionally be difficult.

METHODS

We report the case of a 56-year-old female presenting with a firm pink papule on the left thigh.

RESULTS

Histopathology revealed atypical melanocytes in the epidermis and papillary dermis with numerous mitotic figures and intraepidermal pagetoid spread. Within the dermis was a poorly demarcated collection of epithelioid and spindled cells with intermixed keloidal collagen. The atypical melanocytes stained for MART-1 and S-100, whereas the underlying fibrohistiocytic tumor took up factor XIIIa immunostain, confirming the diagnosis of invasive malignant melanoma occurring in association with a dermatofibroma.

CONCLUSIONS

This case emphasizes the role of immunohistochemical stains in correctly diagnosing melanocytic and histiocytic neoplasms.

Skin adnexal neoplasms--part 1: an approach to tumours of the pilosebaceous unit

Skin adnexal neoplasms comprise a wide spectrum of benign and malignant tumours that exhibit morphological differentiation towards one or more types of adnexal structures found in normal skin. Most adnexal neoplasms are relatively uncommonly encountered in routine practice, and pathologists can recognise a limited number of frequently encountered tumours. In this review, the first of two, the normal histology of the skin adnexal structures is reviewed, and the histological features of selected but important benign and malignant tumours and tumour-like lesions of pilosebaceous origin discussed, with emphasis on the diagnostic approach and pitfalls in histological diagnosis.

[Basal cell carcinoma overlying a dermatofibroma]

The epidermis over a dermatofibroma may show changes that range from simple hyperplasia to the proliferation of basaloid cells, which can become morphologically indistinguishable from basal cell carcinoma. The existence of a true basal cell carcinoma overlying a dermatofibroma is infrequent. These basaloid proliferations have usually been considered to be the result of the inductive effect of the fibrohistiocytic proliferation of the dermatofibroma on the epithelial cells of the hair follicle; therefore, it would be a reactive phenomenon and not truly neoplastic. We describe a case of dermatofibroma that presented with a basaloid proliferation identical in appearance to a basal cell carcinoma on the overlying epidermis.

Anti-cytokeratin 20 staining of Merkel cells helps differentiate basaloid proliferations overlying dermatofibromas from basal cell carcinoma

BACKGROUND

Basaloid epidermal proliferations (BEP), morphologically resembling basal cell carcinoma (BCC), have been described overlying dermatofibromas. Distinguishing the two is important because of non-aggressiveness of BEP and local aggressiveness of BCC. The aim of this study is to determine whether CK20 antibody staining for Merkel cells can be used as an adjunct method to differentiate BEP from BCC.

METHODS

Ten cases of BEP overlying dermatofibromas were selected. Ten cases of BCC were used as control. The two groups were stained with CK20 antibody. Numerical density of CK20 stained Merkel cells in peri-lesional epidermis, BEP and BCC was determined by examining 300 cells at 400X in two separate areas by three independent pathologists. To determine statistical significance, the results were compared using t-test method.

RESULTS

Density of Merkel cells in peri-lesional epidermis was 0.2-0.3%. No merkel cells were detected in the BCC. BEP overlying dermatofibromas showed an obvious increase in CK 20 stained Merkel cells. The difference was statistically significant (P < 0.02) CONCLUSIONS: We report a significant increase in CK20 stained Merkel cells in BEP overlying dermatofibromas as compared to BCC. CK20 antibody staining for Merkel cells can be used as an adjunct method to differentiate BEP overlying dermatofibromas from BCC. Mahmoodi M, Asad H, Salim S, Kantor G, Minimo C. Anti-CK20 staining of Merkel cells helps differentiate basaloid proliferations overlying dermatofibromas from basal cell carcinoma.

Alteration of the TGF-β/SMAD pathway in intrinsically and UV-induced skin aging

In an effort to characterize transforming growth factor (TGF-beta) signaling and to determine its association with the aging and photoaging processes, we directly compared the expressions of TGF-beta/SMAD in intrinsically aged and photoaged human skin in vivo. By using an RNase protection assay and by immunohistochemistry, we found that the expression levels of TbetaRII mRNA and protein in the epidermis of the forearm (sun-exposed) of the elderly were significantly lower than that of the upper-inner arm (sun-protected) skin of the same individual. In the epidermis, the expressions of Smad7 mRNA in both the intrinsically aged and photoaged skin of the elderly were higher than in the sun-protected skin of the young, and this was elevated in the photoaged epidermis. Decreased pSmad2 immunoreactivity was observed in the epidermis of photoaged forearm skin versus matched intrinsically aged skin. This decrease was also found in the epidermis of upper-inner arm skin of the elderly versus the young. These results suggest that the UV-induced down-regulation of TbetaRII and the concerted over-expression of Smad7 may trigger the inhibition of the TGF-beta-induced phosphorylation of Smad2.

Combined Mastocytoma-Junctional Nevus

A unique combined mastocytoma-junctional nevus presented as a 4-mm dark brown macule in the axilla of a 57-year-old white female. Histopathologic examination revealed a proliferation of mast cells partially or completely filling the dermal papillae, hyperpigmentation of the basal keratinocytes and mildly increased basal melanocytes. Overlying the mast cell proliferation, pigmented junctional nevus nests were present. The mast cells were strongly positive with Giemsa stain and mast cell tryptase immunohistochemical stain; nevomelanocytic cells were negative. Nevomelanocytes were strongly immunoreactive for S100, HMB-45, Mart-1, and tyrosinase; mast cells were negative. The clinicopathologic features suggested a synchronous proliferation of 2 cell types in the same small cutaneous field rather than a collision tumor. While the cutaneous mast cells probably originated as a disseminated clone, it is postulated that local mast cell growth factor induced nevomelanocytic proliferation and modulated mast cell growth. In fact, the tumor exhibited strong immunoreactivity for the mast cell growth factor receptor (CD117) in mast cells, basal melanocytes, and nevus nests. The incidence of dual mast cell-melanocytic tumors appears to be very low, as only 3 total cases have now been reported. However, since in patients with multiple mastocytomas only a small fraction of lesions are biopsied, the true incidence may be higher than supposed.

Epidermal basaloid proliferation in cutaneous myxomas

BACKGROUND

Basaloid epidermal proliferations, which histologically resemble basal cell carcinoma, have been described overlying dermatofibromas. Several etiologies have been proposed. Cutaneous myxomas are also benign mesynchymal tumors.

PURPOSE

Basaloid proliferations have been noted overlying cutaneous myxomas. We have undertaken a study to attempt to differentiate whether these are basal cell carcinomas or benign basaloid proliferations.

METHODS

Thirty cases of cutaneous myxomas were included in this study. The lesions were stained with hematoxylin-eosin and alcian blue. Immunohistochemical staining for both epidermal growth factor receptor (EGF-r) and p53 protein was performed on the cutaneous myxomas with epidermal basaloid proliferation.

RESULTS

Of the 30 cases of cutaneous myxomas, nine were found to have an associated overlying basaloid proliferation. The basaloid proliferations were limited to the epidermis overlying the myxoid changes within the dermis. Mitotic figures were rare. Staining for p53 protein showed scattered positive staining in the basal cells in both the basaloid proliferations and adjacent epidermis. EGF-r showed positive staining of the overlying epidermis and basaloid proliferation in five cases.

CONCLUSIONS

We report basaloid proliferations overlying cutaneous myxomas and propose that these represent benign adnexal proliferations rather than superficial basal cell carcinoma and are analogous to the basaloid proliferations overlying dermatofibromas.

Gene expression profile of tissue engineered skin subjected to acute barrier disruption

The main function of the skin is to protect the body from infection, dehydration, and other environmental insults by creating an impermeable barrier of cornified cell layers, the stratum corneum. In contrast to cells in culture, tissue-engineered skin equivalents contain well-developed basal, spinous, granular, and cornified cell layers providing an excellent model to study the tissue response to barrier disruption. After 7 d of culture at the air-liquid interface the barrier of the tissues was disrupted by short exposure to acetone and the global gene expression profile of the tissues was evaluated using DNA microarrays. We found that tissue-engineered skin responds to barrier disruption by a two-wave dynamic response. Early on, the cells upregulate signal transducing, stress, proliferation, and inflammation genes to protect the tissue and possibly to communicate the damage to the immune system and neighboring tissues. At later times, pro-inflammatory cytokines and some growth-related genes are significantly reduced but enzymes that participate in lipid synthesis increase, suggesting that the epidermal cells attempt to restore the lost barrier. Quantitative immunostaining for the proliferation antigen Ki67 revealed that barrier disruption by acetone increased proliferation by 4-fold in agreement with the microarray data and previous in vivo studies. Our work suggests that functional genomics may be used in tissue engineering to understand tissue development, wound regeneration, and response to environmental stimuli. A better understanding of engineered tissues at the molecular level may facilitate their application in the clinic and as biosensors for toxicologic testing.

Keratin 16 expression defines a subset of epithelial cells during skin morphogenesis and the hair cycle

The morphogenesis of skin epithelia and adult hair follicle cycling both require integrated signaling between the epithelium and underlying mesenchyme. Because of their unique regulation, keratin intermediate filaments represent useful markers for the analysis of determination and differentiation processes in complex epithelia, such as the skin. In this study, we analyzed the distribution of mouse type I keratin 16 during skin morphogenesis, in the adult hair cycle, and in challenged epidermis. In mature hair follicles, we find keratin 16 along with its type II keratin partner keratin 6 in the companion layer of the outer root sheath during anagen and in the club hair sheath during catagen and telogen. During embryonic development, the distribution of keratin 16 is uncoupled from its presumed polymerization partner, keratin 6. Keratin 16 initially localizes within early hair germs, but rapidly shifts to a subset of cells at the interface of basal and suprabasal cells above and around the hair germ. The presence of keratin 16 at the transition between mitotically active and differentiating cells is recapitulated in primary keratinocytes cultured in vitro and in phorbol 12-myristate 13-acetate-treated back skin in vivo. We propose that keratin 16 marks cells in an intermediate state of cellular properties in which keratinocytes retain the flexibility required for activities such as cell migration and even mitosis but are resilient enough to provide the structural integrity required of the early suprabasal layers in the context of development, adult hair cycling, and wound repair.