Cellular 'neurothekeoma': an epithelioid variant of dermatofibroma?

AIMS

Cellular neurothekeoma is a rare benign cutaneous neoplasm with conflicting opinions regarding its histogenetic origin (nerve sheath, smooth muscle, myofibroblasts) as well as its relation to myxoid neurothekeoma (nerve sheath myxoma). The present series describes 15 cases whose clinicopathological features indicate a relationship to dermatofibroma.

METHODS AND RESULTS

In this retrospective clinicopathological study, the lesions preferentially occurred in adolescents to young adults on the upper half of the body, often clinically diagnosed as some kind of fibrohistiocytic tissue response. Besides characteristic whorled nests to fascicles of palely eosinophilic epithelioid cells, all lesions showed variable clues pointing to dermatofibroma: acanthosis, ill-defined storiform periphery, peripherally accentuated prominent sclerosis and lymphocytic demarcation/infiltration. Immunohistochemically, all cases were positive with NK1C3 (CD57), KiM1p and proliferating cell nuclear antigen, seven were positive for neurone specific enolase, five for factor XIIIa, six for smooth muscle specific actin and three for E9, an antimetallothionein marker. These findings are similar to those of conventional dermatofibromas, the variability of the profile being best explained by time cycle and function dependent changes. Ultrastructurally, two cases showed microfilaments, attachment plaques, prominent pinocytosis and focal remnants of basal lamina. A careful study of the data and photomicrographs from the literature reveals that in many cases similar conclusions could be reached. Obvious discrepancies are most likely due to the confusion with myxoid neurothekeoma, a well circumscribed, more spindly and myxoid, S100 positive lesion of Schwannian origin.

CONCLUSION

The appearance of dermatofibromas is markedly influenced by architectural, e.g. in deep penetrating dermatofibroma, and/or cellular/stromal criteria, e.g. in epithelioid cell histiocytoma or sclerosing dermatofibroma. Cellular neurothekeoma seems to be a variant of dermatofibromas with both architectural and cellular/stromal peculiarities, i.e. plexiform pattern, epithelioid cytology and stromal sclerosis.

Cutaneous angiosarcoma of the face: clinicopathologic and immunohistochemical study of a case resembling rosacea clinically

An unusual cutaneous angiosarcoma resembling rosacea clinically is described. A 66-year-old man presented with a red discoloration and a diffuse swelling on his nose over a 2-year period that was diagnosed as rosacea. Despite antiinflammatory treatment, the infiltration increased and, after repeated skin biopsies, the diagnosis of a well-differentiated cutaneous angiosarcoma associated with a prominent inflammatory infiltrate was considered. The neoplasm was treated by surgery. The described case emphasizes that diffuse swelling and rosacea-like clinical features should be added to the variably clinical features of cutaneous angiosarcoma.

A new application of BCG antibody for rapid screening of various tissue microorganisms

BACKGROUND

In routine dermatopathology there is growing demand for a simple, fast, cost-effective, and highly sensitive screening tool for the detection of microorganisms.

OBJECTIVE

Our purpose was to determine whether immunostaining with polyclonal anti-Mycobacterium bovis (BCG), which is known for its interspecies cross-reactivity, is a suitable screening method for many common microorganisms in dermatopathologic specimens.

METHODS

A total of 254 formalin-fixed, paraffin-embedded skin specimens of viral, protozoal, fungal, and bacterial infections were stained with appropriate histochemical stains and with anti-BCG.

RESULTS

Anti-BCG labeled bacteria and fungi with high sensitivity and minimal background staining, but did not react with spirochetes, viruses, or protozoa (Leishmania). The quality and sensitivity of anti-BCG staining were superior to conventional histochemical stains.

CONCLUSION

Because of its cross-reactivity with many bacteria and fungi as well as its high sensitivity and minimal background staining, the anti-BCG immunostain is a promising screening tool for the detection of the most common bacterial and fungal microorganisms in paraffin-embedded skin specimens.

Cutaneous reactions at sites of herpes zoster scars: an expanded spectrum

Several types of cutaneous lesions have previously been described at the sites of herpes zoster scars. We describe 16 patients with cutaneous lesions which had developed on herpes zoster scars. Biopsies were taken from these lesions, and a polymerase chain reaction assay was used to detect the viral genome in paraffin-embedded specimens. Histopathological findings enabled diagnosis of nonspecific granulomatous dermatitis in five patients, granulomatous vasculitis in two patients, lichen sclerosus in two patients, and pseudolymphoma, keloid, sarcoidal granuloma, granuloma annulare, granulomatous folliculitis, lichen planus and cutaneous Rosai-Dorfman disease, each in one patient. Varicella-zoster virus DNA was not identified in any of the patients. Granulomatous folliculitis, lichen sclerosus and cutaneous Rosai-Dorfman disease have not previously been described in herpes zoster scars, but they are three new cutaneous reaction patterns that may have developed within these scars. Our investigations indicate that the cutaneous reactions appearing in herpes zoster scars are not due to the persistence of varicella-zoster virus DNA within the lesions.

Absence of anaplastic lymphoma kinase (ALK) and Epstein-Barr virus gene products in primary cutaneous anaplastic large cell lymphoma and lymphomatoid papulosis

The prevalence of the t(2;5)(p23;q35) and/or anaplastic lymphoma kinase (ALK) gene products in cutaneous anaplastic large cell (ALC) lymphomas and a potential precursor lesion, lymphomatoid papulosis (LyP), is controversial. ALK gene products, which are absent from normal lymphohaematopoietic cells, are a phenotypic marker of lymphomas carrying the t(2;5). We used in situ hybridization and immunohistology to screen 14 cutaneous ALC lymphomas, 21 cases of LyP, and one nodal ALC lymphoma associated with LyP for ALK gene products. ALK gene products were not detectable in these cases. In contrast, ALK gene products were found in a lymphonodal ALC lymphoma with subsequent extension to the skin and in t(2;5)-positive cell lines. Detection of the Epstein-Barr virus (EBV)-encoded small nuclear transcripts (EBER), and of immunoglobulin light chain transcripts served to check for the presence of cellular RNA in the tissue sections. EBER transcripts were found in scattered reactive lymphoid cells, but not in atypical or tumour cells. ALK gene expression and EBV infection seem to be a rare finding in cutaneous ALC lymphomas and LyP. This points to a molecular aetiology of primary cutaneous ALC lymphomas and LyP distinct from that of extracutaneous CD30+ lymphoproliferative disease. Detection of the t(2;5) or ALK gene products in cutaneous lymphoproliferative lesions therefore requires exclusion of extracutaneous ALC lymphoma in such patients.

Granular cell dermatofibroma

AIMS

To describe a series of five granular cell dermatofibromas as an unusual and rare manifestation of fibrohistiocytic tissue response.

METHODS AND RESULTS

Five granular cell dermatofibromas were collected out of 136 tumours filed as granular cell tumours. Clinically, all lesions occurred on the shoulder or back of middle-aged adults (two women, three men), mostly with the clinical diagnosis of a fibrohistiocytic lesion. Histology revealed well-circumscribed, dermal to subcutaneous lesions dominated by periodic acid-Schiff (PAS) positive, granular cells. Acanthosis above, as well as storiform arrangement of spindle cells, sclerotic collagen and some interspersed lymphohistiocytic infiltrate at the periphery of the lesion, indicated the fibrohistiocytic origin. Lesions showed prominent reactivity with NK1C3 (CD57), as well as for macrophage markers KiM1p and KP1 (CD68). In contrast to classic Schwannian/neurogenic granular cell tumours, granular cell dermatofibromas were S100 protein negative, but showed variable reactivity for factor XIIIa (10-50%) in 4/5, for smooth muscle specific actin (10-50%) in 2/5 and with E9 (10-30%) in 3/5 lesions. Electron microscopy in one case revealed large pools of phago-lysosomes and variably sized glycogen granules in granular cells.

CONCLUSION

Our series delineates granular cell dermatofibroma as a distinct clinicopathological variant of fibrohistiocytic tissue response which needs to be distinguished from other tumours with granular cell features.

Verocay body--prominent cutaneous schwannoma

We report on eight cases of a distinct variant of cutaneous schwannoma characterized by prominent Verocay body formation (75-100% of the tumor bulk) that may cause considerable diagnostic difficulties. Like ordinary cutaneous schwannomas, these lesions preferred the head and neck region of young adults without sexual predilection and were clinically interpreted as cyst, basal cell carcinoma, or nevus. Histological examination revealed well-circumscribed nodules. Three of them consisted exclusively of nodular or ribbon-like Verocay bodies. A variable admixture of Antoni A or B type of differentiation (< 25%) was seen in five other cases. The following patterns were seen: fascicular spindle-shaped, onion-like epithelioid, myxoid-hypocellular, and degenerated ("ancient") with prominent fibrosis/hyalinosis and occasional bizarre giant cells. Immunohistochemically, the lesions were positive for S-100 protein (and vimentin) but negative for a broad panel of neurogenic and intermediate filament markers. The capsule showed focal labeling for EMA and--when it was markedly thickened--also for SMA. Labeling with E9, an anti-metallothionein marker indicative of cell activity, was negative, underscoring the slow growth potential of these lesions. No recurrence was seen in the six patients with follow-up information. The differential diagnosis includes other lesions with prominent palisading. (Amianthoid) myofibroblastoma and palisading leiomyoma are consistently positive for SMA and desmin, respectively. Palisading cutaneous fibrous histiocytoma and myofibroblastic dermatofibroma are variably positive for Factor XIIIa, SMA, and E9 and/or NK1C3 (CD57). Palisaded encapsulated neuromas are primarilly differentiated by the presence of nerve fibers with myelin sheaths.

Cutaneous adult myofibroma: a vascular neoplasm

Infantile myofibromatosis is a distinctive type of fibromatosis that usually develops during the immediate perinatal period. There are variants with solitary and multiple tumors. Lesions confined to the skin, soft tissue, and bone carry a good prognosis, showing spontaneous regression. The prognosis, however, is much less favorable when visceral lesions are present and the outcome may be fatal. Only recently it became obvious that there is an adult counterpart of infantile myofibromatosis, characterized by solitary lesions that have a predilection for involve the dermis and show no tendency to regression, although they have an entirely benign biological behavior. These lesions have been named cutaneous myofibroma or solitary myofibroma of adults. We have studied the clinical, histopathological and immunohistochemical characteristics of 53 examples of cutaneous adult myofibroma. In addition, 2 cases were examined ultrastructurally. The patients were mostly adults with ages ranging from 6-83 years. The lesions presented as solitary, usually painless nodules of variable duration on the skin, usually located on the extremities. Histopathologically, four patterns were identified: nodular or cellular type, multinodular or biphasic type, leiomyoma-like or fascicular type, and vascular type. A correlation between the histopathologic pattern and the lesional age was observed: vascular type of cutaneous adult myofibroma in early lesions, nodular and multinodular lesions in fully developed lesions, and leiomyoma-like or fascicular type in late lesions. Immunohistochemically, the spindle cells were desmin negative, but expressed immunoreactivity for vimentin, pan-smooth muscle actin, and alpha-smooth muscle actin. Ultrastructurally, neoplastic cells showed characteristics of undifferentiated mesenchymal cells with features of fibroblasts, myofibroblasts and pericytes. Primitive vascular formations were seen in the form of irregular clefts between adjoining cells. We conclude that cutaneous adult myofibroma is a little-known benign vascular neoplasm probably derived from myopericytes.

[Desmoplastic malignant melanoma. Clinical and histopathologic results of a study in 34 patients]

Clinical and histopathological findings of 34 cases of desmoplastic malignant melanoma (DMM) are summarized and compared to the literature. DMM develop mostly in sun damaged skin of elderly patients, they are rare and often nonpigmented tumors that are difficult to diagnose clinically. In all cases the tumor parameters showed level IV or V melanomas (level IV: 55.9%, level IV-V: 14.7%, level V: 29.4%) and the tumor thickness measured 3.85 mm +/- 2.31 mm (1.0-11.0 mm). In 22 cases, the follow-up time was between 2 and 7 years. Local recurrences were observed in 7 ( = 31.8%) patients, metastases in 4 ( = 18.2%) and tumor-related deaths in 3. The prognosis for our patients seems to be slightly better than that described in the literature. The main reason is an improved histological diagnosis of this special type of melanoma. Using immunohistochemical staining with anti-S100 antibody it is possible to establish the melanocytic nature of these fibrotic spindle cell tumors earlier that is, in small initial biopsies, and tumor margins can be defined more accurately. As a consequence, surgery is done earlier and is more likely to be curative.

[Tufted hemangioma. Clinicopathologic and immunohistologic analysis of 5 cases of a distinct entity within the spectrum of capillary hemangioma]

Two female and three male patients with acquired "tufted angioma" are presented. The age of these patients ranged from 10 to 62 years. Two lesions were sited in the head and neck region, two in the upper extremities, and one on the trunk. Clinically, the angiomatous lesions appeared as elevated plaques, flat lesions with papular and macular areas, or erythematous plaques with small nodules. In four cases a biopsy was done, and in one case the tumour was excised. Histologically, the neoplasms were characterized by irregularly distributed vascular tufts in the dermis, and, in one case, in the upper subcutis. The vascular tufts were composed of plump endothelial cells and spindle-shaped pericytes surrounded by crescent-shaped vascular spaces. The positive staining for CD 31 and for CD 34 and alpha-smooth muscle actin, and the negative staining of endothelial cells for factor VIII underline both the existence of two cellular components in tufted angioma and the immaturity of endothelial cells. Evidence of regular mitotic figures in two cases and increased proliferative activity in three out of four cases tested, emphasize the neoplastic nature of slowly growing tufted angioma. Benign tufted angioma is a distinct entity in the spectrum of capillary haemangiomas and must be distinguished from other vascular neoplasms.

T-cell-rich B-cell lymphoma presenting in skin. A clinicopathologic analysis of six cases

We reviewed our experience with six T-cell-rich B-cell lymphomas (TRBL) presenting in skin. Immunohistochemical studies were performed on all biopsies. The lymphoid population consisted mainly of CD3 and/or UCHL-1 (CD45RO) positive T cells. 5 to 15% of the lymphoid cells stained for the B-cell marker L26 (CD20). Monoclonality of the B-cell component was demonstrated in all cases, utilizing either light chain restriction (5 cases) or clonal immunoglobulin heavy chain gene rearrangement by polymerase chain reaction (PCR) (2 cases). One case was confirmed to be monoclonal by both techniques. Additionally, no clonal rearrangements of the T-cell receptor gamma gene were observed. There was considerable morphological variety in these cases. In H&E stained sections, the differential diagnosis included pseudolymphoma, peripheral T-cell lymphoma, Hodgkin's disease, Lennert's lymphoma and a MALT lymphoma. A significant component of monoclonal plasma cells was present in 3 of 6 cases, suggesting a possible origin from cutaneous immunocytoma. In fact, one of our cases was a biphasic lymphoma displaying TRBL with a small focus of immunocytoma. We conclude that immunophenotypic analysis is necessary for the diagnosis of TRBL. Pathologists should be aware of this type of cutaneous B-cell lymphoma to avoid misinterpretation as a pseudolymphoma.

Clear cell dermatofibroma. Case report of an unusual fibrohistiocytic lesion

A case of clear cell dermatofibroma is presented. Clinically, a 41-year-old woman exhibited a hard brown nodule on her instep that was assumed to be a dermatofibroma. Histologically, more than 90% of the lesion was composed of clear cells. Epidermal hyperplasia and a storiform arrangement of spindle cells and sclerotic collagen in some foci at the periphery of the lesion indicated the fibrohistiocytic origin. Moreover, prominent vascularity and some bizarre giant cells in the lower part of the lesion were reminiscent of multinucleate cell angiohistiocytoma. Of a broad panel of antibodies, the lesion was positive only for Factor XIIIa (and vimentin). Ultrastructurally, clear-cell changes corresponded to a mostly translucent cytoplasm, focally with some endoplasmic reticulum and prominent lysosomal structures. A review of 1,496 dermatofibromas seen during the last 15 years at our institute revealed 12 cases (1%) with similar clear-cell changes in a minor part of the infiltrate (less than 10%). The differential diagnosis includes metastases of renal-cell carcinoma, which exhibit more atypia and mitoses and are positive for epithelial cell markers; clear-cell sarcoma, a lesion of tendons or aponeurosis with some moderate cytoplasmic melanin deposition and immunoreactivity with HMB-45; and various non-X histiocytic disorders, such as the predominantly vacuolated type of juvenile (or adult) xanthogranulomas or papular xanthoma, with a mixed infiltrate of various types of mononuclear and multinucleate histiocytes positive with a variety of macrophage markers.

Ultrastructural spectrum of cutaneous nerve sheath myxoma/cellular neurothekeoma

The histogenesis of cutaneous nerve sheath myxoma (NSM)/cellular neurothekeoma (CNT) is still controversial. In this study, we examined the ultrastructural features of 16 NSM (3 classical, 11 CNT, and 2 mixed NSM/CNT). We classified the cells into 4 groups ultrastructurally. Type I cells were undifferentiated polygonal cells with ovoid nuclei, cytoplasmic microfilaments, and occassionally with microfilament-associated dense bodies. In most cells, the cytoplasmic membrane showed focal membranous densities and occasional basal-lamina-like material. This cell type comprised approximately 90% of CNT. Type II cells were more differentiated, had ovoid or spindled shapes, were rich in intracytoplasmic filaments, and were surrounded by continuous basal lamina. These cells were consistent with Schwann cells and were present in the classical and mixed forms of NSM, and in a single case of CNT. Type III cells had features of perineurial cells and were relatively rare in classical NSM. Type IV cells resembled fibroblasts and were encountered in all variants of NSM. These results support the view that 1) the classical NSM has neural (mainly Schwann cell) differentiation, 2) CNT is predominantly composed of undifferentiated cells with partial features of Schwann cells, smooth muscle cells, myofibroblasts and fibroblasts, suggesting a divergent differentiation, and 3) CNT and NSM represent a histologic spectrum, but in CNT, the neural features are not fully expressed.

[Malignant atrophic papulosis]

A 53-year-old woman had noticed numerous papules on her trunk and proximal parts of the limbs. They had healed with a central scar surrounded by a reddish wall. Four months later she had to undergo laparotomy for ileus, resulting from a perforation in the region of the middle jejunum: it was excised and sutured over. At laparotomy white plaque-like lesions were noted on the serosa of both small and large intestine. Histological examination of the jejunal exudate and of a skin biopsy both demonstrated malignant atrophic papulosis (Köhlmeier-Dégos' disease). Treatment with ticlopidine, a platelet-aggregation inhibitor (250 mg twice daily), was initiated and she has now been free of extracutaneous symptoms for 6 years.

[Differences between plaque-like variants of dermatofibrosarcoma protuberans and plaque-like dermal fibromatosis (dermatomyofibroma)]

On the basis of two cases the differences between the plaque-like variant of dermatofibrosarcoma protuberans (PDFSP) and the plaque-like dermal fibromatosis (synonym: dermatomyofibroma; PDF) are presented. PDFSP and PDF are two clinically very similar dermal fibrous proliferations, but differentiation is important because of their different therapy and prognosis. Histologically and immunohistochemically PDFSP and PDF can be recognized as separate entities.

[Acquired benign myofibroma of the skin (adult myofibroma)]

Adult myofibroma is an acquired skin tumour that is histologically identical to infantile myofibroma. Histologically, four tumour variants can be distinguished: leiomyoma type, cellular spindle cell type, haemangiopericytoma or glomus type, and biphasic type. Practical help in diagnosis is supplied by the hamartomatous composition of the leiomyoma-type, hyalinized spindle cell whorls, endothelium-lined haemangiopericytoma-like vascular channels, and desmin-negative, muscle-actin-positive myofibroblasts, which may show spindle cell or undifferentiated mesenchymal cell differentiation. The tumours clinically present as firm, occasionally bluish cutaneous or subcutaneous nodules. Adult myofibroma should be recognized as a distinct benign neoplasm, most probably of vascular origin. Clinicians and dermatopathologists must be aware that lesions identical to those of infantile myofibroma can occur in adults.

Nerve sheath myxoma (neurothekeoma) of the skin: light microscopic and immunohistochemical reappraisal of the cellular variant

Nerve sheath myxoma (NSM) is a rare cutaneous neoplasm, the histogenesis of which is controversial. Fifteen cases of NSM were studied by routine light microscopy and with a broad panel of immunohistochemical stains. NSM were classified into three groups based on cellularity, mucin content and growth pattern. 1) The hypocellular (myxoid) type (5/15 cases) showed frequent encapsulation or sharp circumscription. Immunohistochemically this type was strongly positive for S-100 protein and collagen type IV and variably positive for epithelial membrane antigen. 2) The cellular type (4/15 cases) had scant mucin and ill-defined nodular or infiltrating growth. Immunostaining showed positive reaction for neuron specific enolase (2/4), Leu-7 (1/4) and smooth muscle specific actin (2/4), and was negative with the other antibodies. 3) The "mixed type" (6/15 cases) had variable cellularity and mucin content with poor demarcation and variable immunolabeling. We conclude that: 1) there are major light microscopic and immunohistochemical differences between the classical hypocellular (myxoid) and the cellular forms of NSM (neurothekeoma); 2) while the immunohistochemical results support the presence of nerve sheath differentiation in the classical forms of NSM, and to some extent in the mixed forms, there is an absence of convincing evidence of neural differentiation in the cellular variant by either light microscopy or immunohistochemistry; 3) the variable immunophenotypes suggest that differentiation other than neural may take place in CNT.

Expression of the human progenitor cell antigen CD34 (HPCA-1) distinguishes dermatofibrosarcoma protuberans from fibrous histiocytoma in formalin-fixed, paraffin-embedded tissue

BACKGROUND

Histologic distinction of dermatofibrosarcoma protuberans (DFSP) from fibrous histiocytoma (FH) may be difficult. In addition, differential diagnosis is hampered by the lack of appropriate immunohistochemical markers that reliably distinguish between these two entities.

OBJECTIVE

This study is aimed at the introduction of a monoclonal antibody (anti-human progenitor cell antigen-1; anti-CD34) that distinguishes between DFSP and FH in formalin-fixed, paraffin-embedded tissue.

METHODS

Paraffin-embedded specimens of DFSP, FH, and other soft-tissue tumors were investigated for CD34 expression by anti-human progenitor cell antigen-1/alkaline phosphatase-antialkaline phosphatase immunostaining.

RESULTS

Strong CD34 reactivity was present in each DFSP (n = 19) but was consistently absent from FH (n = 45) and other soft-tissue tumors (n = 47).

CONCLUSION

CD34 immunostaining of paraffin-embedded specimens may be useful in differentiating between DFSP and FH.

[Pigmented Paget's disease and pigmented breast cancer metastasis. Clinical and histologic simulation of malignant melanoma of the breast]

Pigmented epidermotropic breast carcinoma has to be included in the differential diagnosis of pigmented lesions of the breast. Two rare cases of pigmented Paget's disease and pigmented metastatic breast carcinoma are presented, which mimicked malignant melanoma in both clinical and histological criteria.

[Lymphoepithelioma-like carcinoma of the skin]

Lymphoepithelioma-like carcinoma of the skin (LECS) is a rare cutaneous tumour with histological features resembling those of Epstein-Barr virus-induced nasopharyngeal carcinoma. An LECS tumour may mimic lymphoid follicles in its composition. Its distinct histological pattern, however, is based on syncytial nests and cords of large pale-staining epithelial tumour cells surrounded by a dense lymphoplasmacytic infiltrate. Tumour cells show conspicuous vesicular nuclei with delicate chromatin and few prominent nucleoli. Histological differential diagnosis must include malignant lymphomas, Merkel cell tumour, squamous cell carcinoma and cutaneous metastasis of lymphoepithelioma. Immunostaining with anticytokeratin antibodies is highly significant in the differential diagnosis. Histological and immunohistological findings in an LECS removed from the upper lip of a 56-year-old women are reported. Serologic investigations did not indicate EBV-associated tumour growth.

[Systemic proliferative angioendotheliomatosis: a cutaneous manifestation of malignant B-cell lymphomas. Histologic and immunohistologic studies of two cases]

Angioendotheliomatosis proliferans systemisata (AEPS) is a rare disease entity characterized by a predominantly intravascular proliferation of tumour cells. Two forms of AEPS are differentiated: a very rare, benign and self-limiting form, which is endothelial in origin, and a more common, malignant form, which is an angiotropic intravascular malignant B-cell lymphoma. Histological and immunohistological investigations of the malignant form of AEPS are presented: In a 69-year-old woman cutaneous lesions appeared 5 months before the diagnosis of B-immunoblastic lymphoma. In a 57-year-old woman lesions were observed simultaneously with the relapse of a high-grade malignant B-cell lymphoma. Immunohistological identification of the proliferating cell type made diagnosis of intravascular B-cell lymphoma possible in paraffin-embedded biopsies.

[Solitary encapsulated neuroma]

Solitary encapsulated neuroma (EN) is a true neuroma that is seldom diagnosed clinically. EN is the most frequently excised benign neuroma of the skin and has to be included in the differential diagnosis of small nodular facial tumours of middle-aged people. We report histological studies of 79 EN. EN are distinctive true neuromas that can easily be distinguished from all other benign neural neoplasms except the neuromas in the multiple mucosal neuroma syndrome.

[Desmoplastic trichoepithelioma with nevus cell nevi]

Among a total of 270,000 skin biopsies, 87 desmoplastic trichoepitheliomas were identified, 11 (12.6%) of which were associated with nevocytic nevi. Histopathologically we found nevocytes next to horn cysts and thin strands of monomorphous basaloid neoplastic cells in a dense desmoplastic stroma. The frequency of this association suggests that it may be a combined malformation rather than a chance occurrence. On clinical examination most cases had been misdiagnosed as basal cell carcinomas. Most biopsies were taken from the faces of fairly young women.